.-.-.-.-.-

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This is the GRUB.  Welcome.

This file contains instructions for compiling and installing the GRUB.

The Requirements
================

GRUB depends on some software packages installed into your system. If
you don't have any of them, please obtain and install them before
configuring the GRUB.

* GCC 5.1.0 or later
  Experimental support for clang 3.8.0 or later (results in much bigger binaries)
  for i386, x86_64, arm (including thumb), arm64, mips(el), powerpc, sparc64
* GNU Make
* GNU Bison 2.3 or later
* GNU gettext 0.17 or later
* GNU binutils 2.9.1.0.23 or later
* Flex 2.5.35 or later
* Other standard GNU/Unix tools
* a libc with large file support (e.g. glibc 2.1 or later)

On GNU/Linux, you also need:

* libdevmapper 1.02.34 or later (recommended)

For optional grub-emu features, you need:

* SDL (recommended)
* libpciaccess (optional)
* libusb (optional)

To build GRUB's graphical terminal (gfxterm), you need:

* FreeType 2 or later
* GNU Unifont

If you use a development snapshot or want to hack on GRUB you may
need the following.

* Python 2.6 or later
* Autoconf 2.60 or later
* Automake 1.10.1 or later

Prerequisites for make-check:

* qemu, specifically the binary 'qemu-system-i386'
* xorriso 1.2.9 or later, for grub-mkrescue and grub-shell

Configuring the GRUB
====================

The `configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation.  It uses
those values to create a `Makefile' in each directory of the package.
It may also create one or more `.h' files containing system-dependent
definitions.  Finally, it creates a shell script `config.status' that
you can run in the future to recreate the current configuration, a
file `config.cache' that saves the results of its tests to speed up
reconfiguring, and a file `config.log' containing compiler output
(useful mainly for debugging `configure').

If you need to do unusual things to compile the package, please try to
figure out how `configure' could check whether to do them, and mail
diffs or instructions to the address given in the `README' so they can
be considered for the next release.  If at some point `config.cache'
contains results you don't want to keep, you may remove or edit it.

The file `configure.ac' is used to create `configure' by a program
called `autoconf'.  You only need `configure.in' if you want to change
it or regenerate `configure' using a newer version of `autoconf'.

Building the GRUB
=================

The simplest way to compile this package is:

1. `cd' to the directory containing the package's source code.

2. Skip this and following step if you use release tarball and proceed to
     step 4. If you want translations type `./linguas.sh'.
  
  3. Type `./autogen.sh'.

* autogen.sh uses python. By default invocation is "python" but can be
       overriden by setting variable $PYTHON.

4. Type `./configure' to configure the package for your system.
     If you're using `csh' on an old version of System V, you might
     need to type `sh ./configure' instead to prevent `csh' from trying
     to execute `configure' itself.

Running `configure' takes awhile.  While running, it prints some
     messages telling which features it is checking for.

6. Type `make' to compile the package.

7. Optionally, type `make check' to run any self-tests that come with
     the package.

8. Type `make install' to install the programs and any data files and
     documentation.

9. You can remove the program binaries and object files from the
     source code directory by typing `make clean'.  To also remove the
     files that `configure' created (so you can compile the package for
     a different kind of computer), type `make distclean'.  There is
     also a `make maintainer-clean' target, but that is intended mainly
     for the package's developers.  If you use it, you may have to get
     all sorts of other programs in order to regenerate files that came
     with the distribution.

Cross-compiling the GRUB
========================

GRUB defines 3 platforms:

- "Build" is the one which build systems runs on.
  - "Host" is where you execute GRUB utils.
  - "Target" is where GRUB itself runs.

For grub-emu host and target must be the same but may differ from build.

If build and host are different make check isn't available.

If build and host are different man pages are not generated.

As an example imagine you have a build system running on FreeBSD on sparc
which prepares packages for developers running amd64 GNU/Linux laptop and
they need to make images for ARM board running U-boot. In this case:

build=sparc64-freebsd
host=amd64-linux-gnu
target=arm-uboot

For this example the configure line might look like (more details below)
(some options are optional and included here for completeness but some rarely
used options are omitted):

./configure BUILD_CC=gcc BUILD_FREETYPE=freetype-config --host=amd64-linux-gnu
CC=amd64-linux-gnu-gcc CFLAGS="-g -O2" FREETYPE=amd64-linux-gnu-freetype-config
--target=arm --with-platform=uboot TARGET_CC=arm-elf-gcc
TARGET_CFLAGS="-Os -march=armv6" TARGET_CCASFLAGS="-march=armv6"
TARGET_OBJCOPY="arm-elf-objcopy" TARGET_STRIP="arm-elf-strip"
TARGET_NM=arm-elf-nm TARGET_RANLIB=arm-elf-ranlib LEX=gflex

You need to use following options to specify tools and platforms. For minimum
version look at prerequisites. All tools not mentioned in this section under
corresponding platform are not needed for the platform in question.

- For build
    1. BUILD_CC= to gcc able to compile for build. This is used, for
       example, to compile build-gentrigtables which is then run to
       generate sin and cos tables.
    2. BUILD_CFLAGS= for C options for build.
    3. BUILD_CPPFLAGS= for C preprocessor options for build.
    4. BUILD_LDFLAGS= for linker options for build.
    5. BUILD_FREETYPE= for freetype-config for build (optional).

- For host
    1. --host= to autoconf name of host.
    2. CC= for gcc able to compile for host
    3. HOST_CFLAGS= for C options for host.
    4. HOST_CPPFLAGS= for C preprocessor options for host.
    5. HOST_LDFLAGS= for linker options for host.
    6. FREETYPE= for freetype-config for host (optional).
    7. Libdevmapper if any must be in standard linker folders (-ldevmapper) (optional).
    8. Libfuse if any must be in standard linker folders (-lfuse) (optional).
    9. Libzfs if any must be in standard linker folders (-lzfs) (optional).
    10. Liblzma if any must be in standard linker folders (-llzma) (optional).

- For target
    1. --target= to autoconf cpu name of target.
    2. --with-platform to choose firmware.
    3. TARGET_CC= for gcc able to compile for target
    4. TARGET_CFLAGS= for C options for target.
    5. TARGET_CPPFLAGS= for C preprocessor options for target.
    6. TARGET_CCASFLAGS= for assembler options for target.
    7. TARGET_LDFLAGS= for linker options for target.
    8. TARGET_OBJCOPY= for objcopy for target.
    9. TARGET_STRIP= for strip for target.
    10. TARGET_NM= for nm for target.
    11. TARGET_RANLIB= for ranlib for target.

- Additionally for emu, for host and target.
    1. SDL is looked for in standard linker directories (-lSDL) (optional)
    2. libpciaccess is looked for in standard linker directories (-lpciaccess) (optional)
    3. libusb is looked for in standard linker directories (-lusb) (optional)

- Platform-agnostic tools and data.
    1. make is the tool you execute after ./configure.
    2. Bison is specified in YACC= variable
    3. Flex is specified in LEX= variable
    4. GNU unifont and Djvu sans are looked for in standard directories.

Compiling For Multiple Architectures
====================================

You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  `cd' to the directory where you want the object files
and executables to go and run the `configure' script.  `configure'
automatically checks for the source code in the directory that
`configure' is in and in `..'.

Installation Names
==================

By default, `make install' will install the package's files in
`/usr/local/bin', `/usr/local/man', etc.  You can specify an
installation prefix by giving `configure' the option `--prefix=PATH'.

You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.  If
you give `configure' the option `--exec-prefix=PATH', the package will
use PATH as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.

In addition, if you use an unusual directory layout you can give
options like `--bindir=PATH' to specify different values for
particular kinds of files.  Run `configure --help' for a list of the
directories you can set and what kinds of files go in them.

If the package supports it, you can cause programs to be installed
with an extra prefix or suffix on their names by giving `configure'
the option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.

Please note, however, that the GRUB knows where it is located in the
filesystem.  If you have installed it in an unusual location, the
system might not work properly, or at all.  The chief utility of these
options for the GRUB is to allow you to "install" in some alternate
location, and then copy these to the actual root filesystem later.

Sharing Defaults
================

If you want to set default values for `configure' scripts to share,
you can create a site shell script called `config.site' that gives
default values for variables like `CC', `cache_file', and `prefix'.
`configure' looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists.  Or, you can set the
`CONFIG_SITE' environment variable to the location of the site script.
A warning: not all `configure' scripts look for a site script.

Operation Controls
==================

`configure' recognizes the following options to control how it
operates.

`--cache-file=FILE'
     Use and save the results of the tests in FILE instead of
     `./config.cache'.  Set FILE to `/dev/null' to disable caching, for
     debugging `configure'.

`--help'
     Print a summary of the options to `configure', and exit.

`--quiet'
`--silent'
`-q'
     Do not print messages saying which checks are being made.

`--srcdir=DIR'
     Look for the package's source code in directory DIR.  Usually
     `configure' can determine that directory automatically.

`--version'
     Print the version of Autoconf used to generate the `configure'
     script, and exit.
PK��\P��S3W3WNEWSnu�[���New in 2.02:

* New/improved filesystem and disk support:
  * Big-endian UFS1.
  * Experimental 64-bit ext2 support.
  * Various fixes for non-512-byte sector devices.
  * New `proc' filesystem framework, used by LUKS disks.
  * Fix DM-RAID partition handling.
  * New `nativedisk' command to switch from firmware to native disk drivers.
  * Compressed HFS+.
  * DragonFly BSD labels.
  * CBFS (coreboot).
  * Handle partitioned LVM properly.
  * Use LVM UUIDs whenever possible.
  * GPT PReP.
  * New `progress' module that shows progress information while reading
    files.
  * ZFS features support.
  * ZFS LZ4 support.
  * XFS V5 format support.
  * LVM RAID1 support.

* New/improved terminal and video support:
  * Monochrome text (matching `hercules' in GRUB Legacy).
  * Morse code output using system speaker.
  * `spkmodem' output (simple data protocol using system speaker).
  * Handle Japanese special keys.
  * coreboot framebuffer.
  * Serial on ARC.
  * Native vt100 handling for grub-emu, replacing the use of the curses
    library.
  * New gfxmenu options for terminal window positioning, theme background
    image handling, and scrollbar padding, plus `item_pixmap_style' and
    `highlight_overlay'.
  * Support several more image types (paletted and greyscale).

* Boot protocol improvements:
  * Support Apple FAT binaries on non-Apple platforms.
  * Improve FreeDOS direct loading support compatibility.
  * Enable `linux16' on all x86 platforms, not just BIOS.
  * New TrueCrypt ISO loader.
  * multiboot2 boot-services EFI specification.
  * multiboot2 EFI memory map specification.
  * multiboot2 full-file specfication.

* New/improved network support:
  * New variables `net_default_*' containing properties of the default
    interface.
  * Autoload `http' and `tftp' modules if necessary.
  * Improve TFTP robustness.
  * Parse `nd' disk names in GRUB Legacy configuration files.
  * Issue separate DNS queries for IPv4 and IPv6.
  * Support IPv6 Router Advertisement to configure default router.
  * New variable net_<interface>_next_server containing next server
    from BOOTP reply.

* Coreboot improvements:
  * CBFS support both in on-disk images (loopback) and flash.
  * Ability to launch another payload from flash or disk
  * Coreboot framebuffer
  * CBMEMC support (both logging and inspecting logs)
  * Command for inspecting coreboot timestamps (`coreboot_boottime').
  * Command for inspecting coreboot tables (`lscoreboot').
  * New target default_payload.elf.
  * Increased maximal core size.
  * Prefer pmtimer for TSC calibration.

* New/improved platform support:
  * New `efifwsetup', `lsefi' and `connectefi` commands on EFI platforms.
  * New `cmosdump' and `cmosset' commands on platforms with CMOS support.
  * New command `pcidump' for PCI platforms.
  * Improve opcode parsing in ACPI halt implementation.
  * Use the TSC as a possible time source on i386-ieee1275.
  * Merge PowerPC grub-mkrescue implementation with the common one.
  * Support grub-mkrescue on i386-ieee1275, sparc64, bootinfo machines such
    as pSeries, and mips-arc.
  * Make grub-mkrescue better support Apple Intel Macs on CD.
  * Enable GRUB Legacy configuration file parsing on EFI.
  * Support halt for Loongson 2E.
  * ARM U-Boot and EFI ports.
  * Reorganise platform-dependent code in utilities to avoid #ifdef mess.
  * AROS and Haiku support for userspace utilities.
  * Xen PV port.
  * Fix EFI stack alignment.
  * ARM64 EFI port.
  * On Linux, read partition start offsets from sysfs if possible.
  * New grub-macbless utility, and better integration with Mac firmware in
    grub-install.
  * Support Yeeloong 3A.
  * Add `cpuid --pae' option to detect Physical Address Extension on x86.
  * Support for USB debug dongles.
  * Support for *-emu on all platforms (previously only i386/x86_64 worked).
  * Support *-emu on Windows.
  * New platform `none' which builds only user level utilities. This is now
    default if target CPU is not supported.
  * Support for booting little-endian Linux kernel on powerpc.
  * Support network boot with Oracle sun4v vnet devices.
  * Added SAS disks to the IEEE 1275 Open Firmware device list.
  * Try multiple methods for TSC (timestamp counter) calibration - PIT, pmtimer,
    EFI Stall. If everything fails, use hardcoded frequency 800MHz.
  * Support Hyper-V Gen2 platforms which lack PIT for TSC calibration.
  * Map UEFI Persistent Memory to E820 persistent memory.
  * New Xen loader on ARM64.
  * Respect alignment requirement for block device IO buffers on EFI.

* Security:
  * Add optional facility to enforce that all files read by the core image
    from disk have a valid detached digital signature.

* Performance:
  * Avoid costly division operations in many places.
  * New boot time analysis framework (`./configure --enable-boot-time').
  * Initialise USB ports in parallel.
  * New `testspeed' command to test file read speed.
  * Speed-up gfxterm by storing intermediate results in more compact format.
  * Lazy LVM/mdraid scan.
  * Disk hints.

* Scripting:
  * New `eval' and `tr' commands.
  * grub-script-check fails on scripts containing no commands.

* Installation and other utility improvements:
  * Add option to compress files on installation or image creation.
  * Using grub-reboot no longer requires setting `GRUB_DEFAULT=saved'.
  * Support probing EFI System Partition (requires os-prober >= 1.58).
  * Fix inconsistent use of `GRUB_CRYPTODISK_ENABLE' and
    `GRUB_ENABLE_CRYPTODISK'; the latter is now used consistently.
  * grub-mount handles symbolic links to directories.
  * Support disabling submenus with `GRUB_DISABLE_SUBMENU' configuration key
    for grub-mkconfig.
  * grub-install, grub-mknetdir, grub-mkrescue, and grub-mkstandalone
    rewritten in C.  They should now work in supported non-Unix-like
    environments.
  * Native mingw support.
  * Ability to install on EFI under windows.
  * Reorganise timeout handling using new `timeout_style' environment
    variable and `GRUB_TIMEOUT_STYLE' configuration key for grub-mkconfig.
    Menu hotkeys pressed during a hidden timeout now boot the corresponding
    menu entry immediately.
  * New `file' command and grub-file utility to check file types.
  * New syslinux configuration file parser.
  * Set menu entry class to primary OS name returned by os-prober to display
    OS specific icon.
  * On Linux x86 detect EFI word size in grub-install and automatically select
    correct platform (x86_64-efi or i386-efi) to install. Requires Linux kernel
    4.0 or higher.

* Build system:
  * Remove all uses of nested functions; GRUB no longer requires an
    executable stack.
  * Fix documentation build with Texinfo >= 5.1.
  * More robust and documented cross-compiling support.
  * Partial clang support for some platforms (experimental).
  * Partial mingw64 x86_64-efi compile support (highly experimental).
  * Partial mingw32 i386-* (other than already present i386-pc)
    compile support (highly experimental).
  * Support for grub-mkpasswd on Windows.
  * Eliminate the use of AutoGen.  This allowed some performance
    improvements to the build system.
  * Remove variable length arrays.
  * OpenBSD compile and tools support (NetBSD and FreeBSD were already supported).
  * Fix build with FreeType >= 2.5.1.
  * Make gentpl.py compatible with Python 3.  It now requires at least
    Python 2.6.
  * modinfo.sh contains build information now.
  * Added many new tests to improve robustness.
  * Target is built without libgcc now. Necessary builtins are reimplemented
    directly. This removes requirement for target-specific runtime on build
    system.
  * emu libusb support removed (was broken and unmaintained).
  * powerpc64le compile support.
  * Use fixed timestamp when generating GRUB image for reproducible builds.
  * Verify at build time that modules contain only supported relocations and their
    structure matches what boot-time module loader expects.
  * Do not require fonts on powerpc-ieee1275.

* Revision control moved to git.

New in 2.00:

* Appearance:
  * Official theme for gfxmenu (starfield)
  * Menu is organised with submenus.
  * Better default video mode selection using EDID.

* New platforms:
  * Itanium port.
  * Fuloong2F support (including GRUB as firmware)
  * Fuloong2E support (except GRUB as firmware)
  * ARCS (SGI machines) port.
  * qemu -M mips port.

* grub-mount to mount filesystems using GRUB FS drivers and FUSE.

* Changed security default so entries are locked by default if any superuser is
  defined.

* New drivers:
  * EHCI.
  * AHCI.
  * ESCC serial.
  * IEEE1275 serial.
  * EFI serial.
  * Network stack for BIOS, IEEE1275, EMU and EFI, including TFTP, HTTP and DNS.

* New filesystem, filters and disks formats:
  * DVH partition map.
  * Plan9 partition map.
  * Big-endian mdraid.
  * Big-endian cpio.
  * ODC and NEWC cpio.
  * ExFAT.
  * Minix3fs.
  * Big-endian minixfs.
  * RomFS.
  * Squash4.
  * Support non-512B disk blocks.
  * LUKS and GELI support.
  * LDM read support (no install yet).
  * LZOP.

* Improved filesystem and disks formats support:
  * HFS+ label support.
  * Improved reiserfs support.
  * multidevice, mirrored and raidz(2,3) ZFS support.
  * RAID LVM (internal RAIDing) support.
  * ZFS crypto support.
  * ZLE, LZ4 and GZIP on ZFS support.
  * Support ZFS up to 33.
  * HFS string is now treated like mac-roman and not UTF-8
  * HFS mtime support.
  * Improved AFFS and SFS support.
  * LZO-compressed btrfs support.
  * cpio and tar symlinks support.
  * Better FS detection to reduce false positives.

* New boot protocols:
  * Ability to load another coreboot payload when on coreboot.
  * Plan9.
  * Freedos.
  * Ntldr/bootmgr (to load Windows bootloader).
  * chainloader --bpb support to patch FAT or NTFS BPB in memory to correct
    wrong partition offset.
  * PXE chainloading support.
  * Darwin 11 (Mac OS X Lion) protocol support.

* Boot protocol improvements:
  * Multiple initrd support.
  * Basic illumos and xnu autoconfig.

* Testing and debugging:
  * New grub-fstest commands: cat, zfsinfo, testload xnu_uuid
  * grub-fstest recursive directory compare for quickly checking that
    a directory is read correctly.
  * Backtace on crash (if gdb module is loaded, x86 only)
  * Disk cache statistics gathering.
  * GDB stub and GDB support script.
  * "make check" and "make bootcheck" expanded to almost all platforms
    (except i386-ieee1275, mips-arc, sparc64-ieee1275, ia64-efi and emu)
  * New `time' command.

* Performance:
  * Lazy scanning to avoid accessing devices which aren't really used.
    This avoids boot delay due to slow device scanning.
  * Use CPU cache when accessing video memory.
  * Search hints to first try the most likely device when searching for a
    device with given UUID. This avoids slow scanning in most cases.

* Internationalisation:
  * Updated to Unicode 6.0.
  * $"..." syntax for translation in grub scripting language. This allows easy
    translation of grub.cfg at runtime.
  * Translations to many languages included in official distribution.

* Scripting:
  * $grub_cpu and $grub_platform variables for conditioning grub.cfg on platform
    at runtime.
  * $feature_* variables to condition scripts on available features.
  * Use of ids to identify menu entries.
  * all_video module which is empty but depends on all video modules thus
    allowing easy loading of all of them.

* Installation:
  * grub-mknetdir script for easy creation of netbootable GRUB directory.
  * Itanium and mips support in grub-mkrescue.
  * grub-install support for all platforms except emu.
  * PreP partition install support.
  * No files conflict between flavours (except grub-mkrescue for ppc). This
    allows easy install of GRUB for several platforms.
  * grub-mkstandalone script for easy creating of image including all modules
    for platforms with generous limit on image size.
  * program-transform-name now functions according to usual conventions.
    Use --grubdir and --bootdir to get old behaviour.

* ADLER32 and CRC64 support (for XZ and hashsum).

* ofconsole renamed to console

* Experimental support for compiling with Apple toolchain.

* grub-mkdevicemap removed. Now all devices are detected on invocation of
  any grub utility.

New in 1.99:

* Keyboard layouts support.

* New `lsapm' command (i386-pc only).

* Parser for GRUB Legacy configuration files.

* Support RAID on virtio devices.

* Remove deprecated `root' command.

* New `euro.pf2' font which supports most European languages.

* Avoid opening the same device twice on Open Firmware platforms.

* Extend `vbeinfo' and `vbetest' commands to non-VBE graphics, as
  `videoinfo' and `videotest'.

* New `lsefisystab', `lssal', and `lsefimmap' commands on EFI platforms.

* Support explicit user claim that a device is BIOS-visible.  Devices
  listed in device.map will be assumed to be readable using only BIOS
  facilities, rather than anything more complex such as LVM or RAID.

* New bash-completion script for GRUB utilities.

* Use ACPI to shut down if possible.

* New `lsacpi' command.

* Btrfs support.

* New `--boot-directory' option to `grub-install', `grub-reboot', and
  `grub-set-default', with clearer semantics than the previous
  `--root-directory' option.

* Rename CD-ROM device to "cd" on BIOS platforms.

* Transparent decompression filters.

* Simpler PXE image generation.  New `grub-mknetdir' utility to generate
  netboot directory trees.

* New relocator.  Allows for more kernel support and more
  straightforward loader writing.

* Handle USB pendrives exposed as floppies.

* New Automake-based build system.

* Add `sendkey' command (i386-pc only).

* ZFS support.

* Support 1.x versions of mdadm metadata.

* Fix corruption when reading Reiserfs directory entries.

* Bidirectional text and diacritics support.

* Skip LVM snapshots.

* MIPS Yeeloong firmware port.

* Change grub-mkdevicemap to emit /dev/disk/by-id/ names where possible
  on GNU/Linux.

* Add `grub-mkconfig' support for Xen with Linux.

* Add `grub-mkconfig' support for initrd images on Fedora 13.

* Support >3GiB and <16MiB RAM in i386-qemu.

* Add support for Cirrus 5446 and Bochs video cards.

* Load more appropriate video drivers automatically in `grub-mkconfig'.

* USB improvements, including hotplugging/hotunplugging, hub support,
  and USB serial support.

* AMD Geode CS5536 support.

* Extensive updates to the Texinfo documentation.

* Handle symbolic links under /dev/mapper on GNU/Linux.

* Handle installation across multiple partition table types.

* Add `cmostest' command (i386/x86_64 only).

* Add support for DM-RAID disk devices on GNU/Linux.

* Remove `grub-mkisofs'.  `grub-mkrescue' now uses GNU xorriso to build
  CD images.

* `grub-mkrescue' support for EFI, coreboot, and QEMU platforms.

* Unify `grub-mkimage', `grub-setup', and `grub-install' source code
  across platforms.

* Fix VGA (as opposed to VBE) video driver, formerly a terminal driver.

* Add menu hotkey support.

* Add support for the nilfs2 filesystem.

* `grub-probe' and `grub-mkconfig' support for NetBSD.

* Support setting a background image in `grub-mkconfig'.

* Support multiple terminals in `grub-mkconfig'.

* Regexp support.

* MIPS multiboot2 support.

* Multiboot2 tag support.

* sunpc partition table support.

* Add a number of new language features to GRUB script: `for', `while',
  `until', `elif', function parameters, `break', `continue', `shift',
  multi-line quoted strings, positional parameters with `setparams',
  `return', filename wildcard expansion, and `!'.

* Support nested partition tables.  GRUB now prefers to name partitions
  in the form `(hd0,msdos1,bsd1)' rather than `(hd0,1,a)'.

* Speed up consecutive hostdisk operations on the same device.

* Compile parts of `grub-emu' as modules.

New in 1.98 - 2010-03-06:

* Multiboot on EFI support.

* Graphical menu support.

* MIPS support.

* Saved default menu entry support, with new utilities `grub-reboot' and
  `grub-set-default'.

* Unit testing framework.

* Support for multiple terminals.

* Encrypted password support, with a new utility `grub-mkpasswd-pbkdf2'.

* `grub-mkfloppy' removed; use `grub-mkrescue' to create floppy images.

* Add grub-probe support for GNU/Hurd.

* Add support for gettext.

New in 1.97:

* Add support for loading XNU (MacOS X kernel).

* ACPI override support.

* Integrated gptsync.

* Password protection support.

* Partition manipulation tool.

* Add `keystatus' command.

* Unicode fonts are now used by default.

* Add `hdparm' command.

* Add support for getting the current date and time from CMOS as variables.

* Add `drivemap' command.

* Add support for RAID levels 4,6 and 10.

* update-grub is replaced by grub-mkconfig.

* When booting from PXE, PXE can be used to load files.

* High resolution timer support.

* Image loaders now support IO buffering.

* Add `crc' command.

* Add Cygwin support.

* Add x86_64 EFI support.

* Use LZMA compression instead of LZO.

* Support for saving the environment from and loading the environment
  from a file.

* Allow the UUID to be used as device name.

* The `search' command can use UUIDs now.

* Add support for IEEE 1275 on i386.

* Create partmap.lst and use it to automatically load partition map
  modules.

* grub-mkconfig supports os-prober to add operating systems to the
  boot menu.

* The ATA driver supports devices bigger than 2 TiB.

* Add support for the UDF, AFS and EXT4 filesystems.

* The ISO9660 filesystem supports the Joliet extension

* Add support for loading kernels of FreeBSD, NetBSD and OpenBSD.

* Add new command `sleep'.

* Support for direct access to AT keyboards.

* New utility `grub-fstest'.

New in 1.96 - 2008-02-03:

* The license term is changed to GNU General Public License Version 3.

* grub-emu is made optional.  Now you have to use
  `--enable-grub-emu' to enable it.

* Add Multiboot2 support.

* grub-emu can access the host filesystem now.

* Add support for the NTFS, cpio/tar and Reiserfs filesystems.

* Add support for ATA/ATAPI.

* Add update-grub script to generate grub.cfg.

* Add grub-mkrescue script to generate floppy or ElTorito images
  (i386-pc only).

* Add support for background images in gfxterm (background_image command).

* Add support for detection of 64-bit support in CPU (cpuid command).

* GPT is now enabled in i386-pc target.

* Add grub-install for EFI.

* Ported to the following new platforms: Efika, coreboot (a.k.a. LinuxBIOS),
  OLPC XO.

* Add support for colored menu (menu_color_normal and menu_color_highlight
  variables).

* Fix support for loading Linux zImages (such as memtest86).

New in 1.95 - 2006-10-15:

* Number partitions from 1 instead of 0. For instance, the first
  partition of "hd0" is now "hd0,1" but not "hd0,0".

* grub-probefs is renamed to grub-probe, and supports printing a
  guessed OS device name and a GRUB drive name.

* RAID and LVM support is added.

* New command, echo.

* The disk API is changed to support 64-bit addressing.

* A TGA loader is added for the video API.

New in 1.94 - 2006-06-04:

* Fix several serious bugs in HFS+.

* Add experimental EFI support. Chainloading and Linux loading are
  supported at the moment.

* Add a new command "blocklist" to show a block list.

* Use --with-platform to specify a boot environment. For now, efi,
  ieee1275 and pc are supported.

* Use the filename "kernel.elf" instead of "grubof" on ieee1275.

* Install GRUB into pkglibdir instead of pkgdatadir.

* Support environmental variables. You can export variables by the
  command "export".

* Remove the commands "default" and "timeout". They are now variables.

* Add the commands "source" and "." to include a file.

* Implement experimental Video API and a new terminal "gfxterm" based
  on the Video API.

New in 1.93 - 2006-03-10:

* Add support for the HFS+ wrapper.

* Major improvements to scripting support.

* Menu entries are now scriptable.

New in 1.92 - 2005-12-25:

* Add support for GPT partition table format.

* Add a new command "play" to play an audio file on PC.

* Add support for Linux/ADFS partition table format.

* Add support for BASH-like scripting.

* Add support for Apple HFS+ filesystems.

New in 1.91 - 2005-10-15:

* Add support for LZO version 2.

* Support completion in the entry editor.

* Add VBE support.

* New commands, "search", "vbetest" and "vbeinfo".

* The option BOOT_IMAGE is passed to Linux.

* Add support for automatic decompression for gzip.

* Add support for terminfo and serial.

* Add support for x86_64.

* GRUB itself is a Multiboot-compliant kernel.

* Add new filesystems: XFS, SFS, and AFFS.

New in 1.90 - 2005-08-07:

* Rename the project name PUPA to GRUB. Now this version is the
  developmental version of GRUB officially.

* The GRUB emulator ``grub-emu'' is added.

* Add support for newworld Mac. This should work with other
  PowerPC-based machines as well, if they use IEEE 1275
  (Open Firmware).

* Too many changes to describe. Look at ChangeLog for more details.

New in 0.7:

* Problems in cross-compiling PUPA are fixed.

* Use -mrtd and -mregparm=3 to reduce the generated code sizes.	This
  means that any missing prototypes could be fatal. Also, you must take
  care when writing assembly code. See the comments at the beginning of
  startup.S, for more details.

* New utility, ``pupa-setup''. This sets up PUPA to make it bootable
  from a real disk.

* New commands, "prefix", "insmod", "rmmod" and "lsmod" are added into
  the rescue mode to manipulate PUPA modules.

* Linux support is added. Initrd is not support yet.

* Reduce the size of a core image significantly by compressing a large
  part of the core image and decompressing itself at boot time. The
  currently used algorithm is LZO (more precisely, LZO1X-999). So you
  have to install LZO to build PUPA. See
  <http://www.oberhumer.com/opensource/lzo/>, for more information.

New in 0.6 - 2002-12-27, Yoshinori K. Okuji:

* The chainloader and the FAT filesystem are modularized.

* The structure of the source tree is a bit changed.

* Support for building loadable modules is added.

* Some generic parts of pupa-mkimage are segregated.

* Some documentation files are added, according to the GNU Coding
  Standards.
PK��\�+�!!READMEnu�[���This is GRUB 2, the second version of the GRand Unified Bootloader.
GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more
robust, more powerful, and more portable.

See the file NEWS for a description of recent changes to GRUB 2.

See the file INSTALL for instructions on how to build and install the
GRUB 2 data and program files.

Please visit the official web page of GRUB 2, for more information.
The URL is <http://www.gnu.org/software/grub/grub.html>.

More extensive documentation is available in the Info manual,
accessible using 'info grub' after building and installing GRUB 2.

There are a number of important user-visible differences from the
first version of GRUB, now known as GRUB Legacy. For a summary, please
see:

info grub Introduction 'Changes from GRUB Legacy'
PK��\���vvTHANKSnu�[���GRUB 2 would not be what it is today without the invaluable help of
everybody who was kind enough to spend time testing it and reporting
bugs.

The following people made especially gracious contributions of their
time and energy in helping to track down bugs, add new features, and
generally assist in the GRUB 2 maintainership process:

Andrey Shuvikov <mr_hyro@yahoo.com>
Bibo Mao <bibo.mao@intel.com>
David Miller <davem@davemloft.net>
Guillem Jover <guillem@hadrons.org>
Harley D. Eades III <hde@foobar-qux.org>
Hitoshi Ozeki <h-ozeki@ck2.so-net.ne.jp>
Hollis Blanchard <hollis@penguinppc.org>
Jeroen Dekkers <jeroen@dekkers.cx>
Johan Rydberg <jrydberg@gnu.org>
Marco Gerards <marco@gnu.org>
Michael Guntsche <mike@it-loops.com>
NIIBE Yutaka <gniibe@m17n.org>
Omniflux <omniflux@omniflux.com>
Robert Bihlmeyer <robbe@orcus.priv.at>
Roger Leigh <rleigh@whinlatter.ukfsn.org>
Ruslan Nikolaev <nruslan@mail.com>
Timothy Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Tomas Ebenlendr <ebik@ucw.cz>
Tristan Gingold  <tristan.gingold@bull.net>
Tsuneyoshi Yasuo <tuneyoshi@naic.co.jp>
Vesa Jaaskelainen  <chaac@nic.fi>
Vincent Guffens <guffens@inma.ucl.ac.be>
Vincent Pelletier <subdino2004@yahoo.fr>
Vladimir Serbinenko <phcoder@gmail.com>

Also, we thank the projects GNU Automake and LZMA. Some code
was stolen from them.

This project was supported by Information-technology Promotion Agency,
Japan.
PK��\	��>>TODOnu�[���
Before working on improving GRUB, it's very important that you
make contact with the core GRUB developers. Things herein might be
slightly out of date or otherwise not easy to understand at first
glance. So write to <grub-devel@gnu.org> first.

For bug tracking, refer to:

http://savannah.gnu.org/bugs/?group=grub
PK��\6ʁ�;@;@font_char_metrics.pngnu�[����PNG

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<title>GNU GRUB Developers Manual 2.03</title>

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<h1 class="settitle" align="center">GNU GRUB Developers Manual 2.03</h1>

<a name="SEC_Contents"></a>
<h2 class="contents-heading">Table of Contents</h2>

<ul class="no-bullet">
  <li><a name="toc-Getting-the-source-code-1" href="#Getting-the-source-code">1 Getting the source code</a></li>
  <li><a name="toc-Coding-style-1" href="#Coding-style">2 Coding style</a>
  <ul class="no-bullet">
    <li><a name="toc-Naming-Conventions-1" href="#Naming-Conventions">2.1 Naming Conventions</a></li>
    <li><a name="toc-Functions-1" href="#Functions">2.2 Functions</a></li>
    <li><a name="toc-Variables-1" href="#Variables">2.3 Variables</a></li>
    <li><a name="toc-Types-1" href="#Types">2.4 Types</a></li>
    <li><a name="toc-Macros-1" href="#Macros">2.5 Macros</a></li>
    <li><a name="toc-Comments-1" href="#Comments">2.6 Comments</a></li>
    <li><a name="toc-Multi_002dLine-Comments-1" href="#Multi_002dLine-Comments">2.7 Multi-Line Comments</a></li>
  </ul></li>
  <li><a name="toc-Finding-your-way-around-1" href="#Finding-your-way-around">3 Finding your way around</a></li>
  <li><a name="toc-Contributing-changes" href="#Contributing-Changes">4 Contributing changes</a>
  <ul class="no-bullet">
    <li><a name="toc-Getting-started-1" href="#Getting-started">4.1 Getting started</a></li>
    <li><a name="toc-Typical-Developer-Experience-1" href="#Typical-Developer-Experience">4.2 Typical Developer Experience</a></li>
    <li><a name="toc-When-you-are-approved-for-write-access-to-project_0027s-files-1" href="#When-you-are-approved-for-write-access-to-project_0027s-files">4.3 When you are approved for write access to project&rsquo;s files</a></li>
  </ul></li>
  <li><a name="toc-Porting-1" href="#Porting">5 Porting</a></li>
  <li><a name="toc-Error-Handling-1" href="#Error-Handling">6 Error Handling</a></li>
  <li><a name="toc-Stack-and-heap-size-1" href="#Stack-and-heap-size">7 Stack and heap size</a></li>
  <li><a name="toc-BIOS-port-memory-map-1" href="#BIOS-port-memory-map">8 BIOS port memory map</a></li>
  <li><a name="toc-Video-Subsystem-1" href="#Video-Subsystem">9 Video Subsystem</a>
  <ul class="no-bullet">
    <li><a name="toc-Video-API-1" href="#Video-API">9.1 Video API</a>
    <ul class="no-bullet">
      <li><a name="toc-grub_005fvideo_005fsetup" href="#grub_005fvideo_005fsetup">9.1.1 grub_video_setup</a></li>
      <li><a name="toc-grub_005fvideo_005frestore" href="#grub_005fvideo_005frestore">9.1.2 grub_video_restore</a></li>
      <li><a name="toc-grub_005fvideo_005fget_005finfo" href="#grub_005fvideo_005fget_005finfo">9.1.3 grub_video_get_info</a></li>
      <li><a name="toc-grub_005fvideo_005fget_005fblit_005fformat" href="#grub_005fvideo_005fget_005fblit_005fformat">9.1.4 grub_video_get_blit_format</a></li>
      <li><a name="toc-grub_005fvideo_005fset_005fpalette" href="#grub_005fvideo_005fset_005fpalette">9.1.5 grub_video_set_palette</a></li>
      <li><a name="toc-grub_005fvideo_005fget_005fpalette" href="#grub_005fvideo_005fget_005fpalette">9.1.6 grub_video_get_palette</a></li>
      <li><a name="toc-grub_005fvideo_005fset_005farea_005fstatus" href="#grub_005fvideo_005fset_005farea_005fstatus">9.1.7 grub_video_set_area_status</a></li>
      <li><a name="toc-grub_005fvideo_005fget_005farea_005fstatus" href="#grub_005fvideo_005fget_005farea_005fstatus">9.1.8 grub_video_get_area_status</a></li>
      <li><a name="toc-grub_005fvideo_005fset_005fviewport" href="#grub_005fvideo_005fset_005fviewport">9.1.9 grub_video_set_viewport</a></li>
      <li><a name="toc-grub_005fvideo_005fget_005fviewport" href="#grub_005fvideo_005fget_005fviewport">9.1.10 grub_video_get_viewport</a></li>
      <li><a name="toc-grub_005fvideo_005fset_005fregion" href="#grub_005fvideo_005fset_005fregion">9.1.11 grub_video_set_region</a></li>
      <li><a name="toc-grub_005fvideo_005fget_005fregion" href="#grub_005fvideo_005fget_005fregion">9.1.12 grub_video_get_region</a></li>
      <li><a name="toc-grub_005fvideo_005fmap_005fcolor" href="#grub_005fvideo_005fmap_005fcolor">9.1.13 grub_video_map_color</a></li>
      <li><a name="toc-grub_005fvideo_005fmap_005frgb" href="#grub_005fvideo_005fmap_005frgb">9.1.14 grub_video_map_rgb</a></li>
      <li><a name="toc-grub_005fvideo_005fmap_005frgba" href="#grub_005fvideo_005fmap_005frgba">9.1.15 grub_video_map_rgba</a></li>
      <li><a name="toc-grub_005fvideo_005funmap_005fcolor" href="#grub_005fvideo_005funmap_005fcolor">9.1.16 grub_video_unmap_color</a></li>
      <li><a name="toc-grub_005fvideo_005ffill_005frect" href="#grub_005fvideo_005ffill_005frect">9.1.17 grub_video_fill_rect</a></li>
      <li><a name="toc-grub_005fvideo_005fblit_005fglyph" href="#grub_005fvideo_005fblit_005fglyph">9.1.18 grub_video_blit_glyph</a></li>
      <li><a name="toc-grub_005fvideo_005fblit_005fbitmap" href="#grub_005fvideo_005fblit_005fbitmap">9.1.19 grub_video_blit_bitmap</a></li>
      <li><a name="toc-grub_005fvideo_005fblit_005frender_005ftarget" href="#grub_005fvideo_005fblit_005frender_005ftarget">9.1.20 grub_video_blit_render_target</a></li>
      <li><a name="toc-grub_005fvideo_005fscroll" href="#grub_005fvideo_005fscroll">9.1.21 grub_video_scroll</a></li>
      <li><a name="toc-grub_005fvideo_005fswap_005fbuffers" href="#grub_005fvideo_005fswap_005fbuffers">9.1.22 grub_video_swap_buffers</a></li>
      <li><a name="toc-grub_005fvideo_005fcreate_005frender_005ftarget" href="#grub_005fvideo_005fcreate_005frender_005ftarget">9.1.23 grub_video_create_render_target</a></li>
      <li><a name="toc-grub_005fvideo_005fdelete_005frender_005ftarget" href="#grub_005fvideo_005fdelete_005frender_005ftarget">9.1.24 grub_video_delete_render_target</a></li>
      <li><a name="toc-grub_005fvideo_005fset_005factive_005frender_005ftarget" href="#grub_005fvideo_005fset_005factive_005frender_005ftarget">9.1.25 grub_video_set_active_render_target</a></li>
      <li><a name="toc-grub_005fvideo_005fget_005factive_005frender_005ftarget" href="#grub_005fvideo_005fget_005factive_005frender_005ftarget">9.1.26 grub_video_get_active_render_target</a></li>
    </ul></li>
    <li><a name="toc-Example-usage-of-Video-API-1" href="#Example-usage-of-Video-API">9.2 Example usage of Video API</a>
    <ul class="no-bullet">
      <li><a name="toc-Example-of-screen-setup" href="#Example-of-screen-setup">9.2.1 Example of screen setup</a></li>
      <li><a name="toc-Example-of-setting-up-console-viewport" href="#Example-of-setting-up-console-viewport">9.2.2 Example of setting up console viewport</a></li>
    </ul></li>
    <li><a name="toc-Bitmap-API-1" href="#Bitmap-API">9.3 Bitmap API</a>
    <ul class="no-bullet">
      <li><a name="toc-grub_005fvideo_005fbitmap_005fcreate" href="#grub_005fvideo_005fbitmap_005fcreate">9.3.1 grub_video_bitmap_create</a></li>
      <li><a name="toc-grub_005fvideo_005fbitmap_005fdestroy" href="#grub_005fvideo_005fbitmap_005fdestroy">9.3.2 grub_video_bitmap_destroy</a></li>
      <li><a name="toc-grub_005fvideo_005fbitmap_005fload" href="#grub_005fvideo_005fbitmap_005fload">9.3.3 grub_video_bitmap_load</a></li>
      <li><a name="toc-grub_005fvideo_005fbitmap_005fget_005fwidth" href="#grub_005fvideo_005fbitmap_005fget_005fwidth">9.3.4 grub_video_bitmap_get_width</a></li>
      <li><a name="toc-grub_005fvideo_005fbitmap_005fget_005fheight" href="#grub_005fvideo_005fbitmap_005fget_005fheight">9.3.5 grub_video_bitmap_get_height</a></li>
      <li><a name="toc-grub_005fvideo_005fbitmap_005fget_005fmode_005finfo" href="#grub_005fvideo_005fbitmap_005fget_005fmode_005finfo">9.3.6 grub_video_bitmap_get_mode_info</a></li>
      <li><a name="toc-grub_005fvideo_005fbitmap_005fget_005fdata" href="#grub_005fvideo_005fbitmap_005fget_005fdata">9.3.7 grub_video_bitmap_get_data</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-PFF2-Font-File-Format-1" href="#PFF2-Font-File-Format">10 PFF2 Font File Format</a>
  <ul class="no-bullet">
    <li><a name="toc-Introduction-1" href="#Introduction">10.1 Introduction</a>
    <ul class="no-bullet">
      <li><a name="toc-Goals-of-the-GRUB-Font-Format" href="#Goals-of-the-GRUB-Font-Format">10.1.1 Goals of the GRUB Font Format</a></li>
      <li><a name="toc-Why-Another-Font-Format_003f" href="#Why-Another-Font-Format_003f">10.1.2 Why Another Font Format?</a></li>
    </ul></li>
    <li><a name="toc-File-Structure-1" href="#File-Structure">10.2 File Structure</a>
    <ul class="no-bullet">
      <li><a name="toc-Section-Types" href="#Section-Types">10.2.1 Section Types</a></li>
    </ul></li>
    <li><a name="toc-Font-Metrics-1" href="#Font-Metrics">10.3 Font Metrics</a></li>
  </ul></li>
  <li><a name="toc-Graphical-Menu-Software-Design-1" href="#Graphical-Menu-Software-Design">11 Graphical Menu Software Design</a>
  <ul class="no-bullet">
    <li><a name="toc-Introduction-2" href="#Introduction_005f2">11.1 Introduction</a></li>
    <li><a name="toc-Startup-Sequence-1" href="#Startup-Sequence">11.2 Startup Sequence</a></li>
    <li><a name="toc-GUI-Components-1" href="#GUI-Components">11.3 GUI Components</a></li>
    <li><a name="toc-Command-Line-Window-1" href="#Command-Line-Window">11.4 Command Line Window</a></li>
  </ul></li>
  <li><a name="toc-Lockdown-framework-1" href="#Lockdown-framework">12 Lockdown framework</a></li>
  <li><a name="toc-Copying-This-Manual-1" href="#Copying-This-Manual">Appendix A Copying This Manual</a>
  <ul class="no-bullet">
    <li><a name="toc-GNU-Free-Documentation-License-1" href="#GNU-Free-Documentation-License">A.1 GNU Free Documentation License</a>
    <ul class="no-bullet">
      <li><a name="toc-ADDENDUM_003a-How-to-use-this-License-for-your-documents" href="#ADDENDUM_003a-How-to-use-this-License-for-your-documents">A.1.1 ADDENDUM: How to use this License for your documents</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Index-1" href="#Index">Index</a></li>
</ul>
</div>

<a name="Top"></a>
<div class="header">
<p>
Next: <a href="#Getting-the-source-code" accesskey="n" rel="next">Getting the source code</a>, Up: <a href="dir.html#Top" accesskey="u" rel="up">(dir)</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GNU-GRUB-developer-manual"></a>
<h1 class="top">GNU GRUB developer manual</h1>

<p>This is the developer documentation of GNU GRUB, the GRand Unified Bootloader,
a flexible and powerful boot loader program for a wide range of
architectures.
</p>
<p>This edition documents version 2.03.
</p>
<p>This developer manual is for GNU GRUB (version 2.03,
17 March 2026).
</p>
<p>Copyright &copy; 1999,2000,2001,2002,2004,2005,2006,2008,2009,2010,2011 Free Software Foundation, Inc.
</p>
<blockquote>
<p>Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no
Invariant Sections.
</p></blockquote>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Getting-the-source-code" accesskey="1">Getting the source code</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Coding-style" accesskey="2">Coding style</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Finding-your-way-around" accesskey="3">Finding your way around</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Contributing-Changes" accesskey="4">Contributing Changes</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Porting" accesskey="5">Porting</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Error-Handling" accesskey="6">Error Handling</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Stack-and-heap-size" accesskey="7">Stack and heap size</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#BIOS-port-memory-map" accesskey="8">BIOS port memory map</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Video-Subsystem" accesskey="9">Video Subsystem</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#PFF2-Font-File-Format">PFF2 Font File Format</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Graphical-Menu-Software-Design">Graphical Menu Software Design</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Lockdown-framework">Lockdown framework</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Copying-This-Manual">Copying This Manual</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Copying This Manual
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Index">Index</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Getting-the-source-code"></a>
<div class="header">
<p>
Next: <a href="#Coding-style" accesskey="n" rel="next">Coding style</a>, Previous: <a href="#Top" accesskey="p" rel="prev">Top</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Getting-the-source-code-1"></a>
<h2 class="chapter">1 Getting the source code</h2>

<p>GRUB is maintained using the <a href="GIT revision
control system">GIT revision
control system</a>.  To fetch:
</p>
<div class="example">
<pre class="example">git clone git://git.sv.gnu.org/grub.git
</pre></div>

<p>Web access is available under
</p><div class="example">
<pre class="example">http://git.savannah.gnu.org/cgit/grub.git/
</pre></div>

<p>The branches available are:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>master</samp>&rsquo;</dt>
<dd><p>Main development branch.
</p></dd>
<dt>&lsquo;<samp>grub-legacy</samp>&rsquo;</dt>
<dd><p>GRUB 0.97 codebase. Kept for reference and legal reasons
</p></dd>
<dt>&lsquo;<samp>multiboot</samp>&rsquo;</dt>
<dd><p>Multiboot specfication
</p></dd>
<dt>&lsquo;<samp>multiboot2</samp>&rsquo;</dt>
<dd><p>Multiboot2 specfication
</p></dd>
<dt>&lsquo;<samp>developer branches</samp>&rsquo;</dt>
<dd><p>Prefixed with developer name. Every developer of a team manages his own branches.
      Developer branches do not need changelog entries.
</p></dd>
</dl>

<p>Once you have used <kbd>git clone</kbd> to fetch an initial copy of a branch, you
can use <kbd>git pull</kbd> to keep it up to date.  If you have modified your
local version, you may need to resolve conflicts when pulling.
</p>
<hr>
<a name="Coding-style"></a>
<div class="header">
<p>
Next: <a href="#Finding-your-way-around" accesskey="n" rel="next">Finding your way around</a>, Previous: <a href="#Getting-the-source-code" accesskey="p" rel="prev">Getting the source code</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Coding-style-1"></a>
<h2 class="chapter">2 Coding style</h2>

<p>Basically we follow the <a href="http://www.gnu.org/prep/standards_toc.html">GNU Coding Standards</a>. We define additional conventions for GRUB here.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Naming-Conventions" accesskey="1">Naming Conventions</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Functions" accesskey="2">Functions</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Variables" accesskey="3">Variables</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Types" accesskey="4">Types</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Macros" accesskey="5">Macros</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Comments" accesskey="6">Comments</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Multi_002dLine-Comments" accesskey="7">Multi-Line Comments</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Naming-Conventions"></a>
<div class="header">
<p>
Next: <a href="#Functions" accesskey="n" rel="next">Functions</a>, Up: <a href="#Coding-style" accesskey="u" rel="up">Coding style</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Naming-Conventions-1"></a>
<h3 class="section">2.1 Naming Conventions</h3>

<p>All global symbols (i.e. functions, variables, types, and macros) must have the prefix grub_ or GRUB_. The all capital form is used only by macros.
</p>
<hr>
<a name="Functions"></a>
<div class="header">
<p>
Next: <a href="#Variables" accesskey="n" rel="next">Variables</a>, Previous: <a href="#Naming-Conventions" accesskey="p" rel="prev">Naming Conventions</a>, Up: <a href="#Coding-style" accesskey="u" rel="up">Coding style</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Functions-1"></a>
<h3 class="section">2.2 Functions</h3>

<p>If a function is global, its name must be prefixed with grub_ and must consist of only small letters. If the function belongs to a specific function module, the name must also be prefixed with the module name. For example, if a function is for file systems, its name is prefixed with grub_fs_. If a function is for FAT file system but not for all file systems, its name is prefixed with grub_fs_fat_. The hierarchy is noted this way.
</p>
<p>After a prefix, a function name must start with a verb (such as get or is). It must not be a noun. Some kind of abbreviation is permitted, as long as it wouldn&rsquo;t make code less readable (e.g. init).
</p>
<p>If a function is local, its name may not start with any prefix. It must start with a verb.
</p>
<hr>
<a name="Variables"></a>
<div class="header">
<p>
Next: <a href="#Types" accesskey="n" rel="next">Types</a>, Previous: <a href="#Functions" accesskey="p" rel="prev">Functions</a>, Up: <a href="#Coding-style" accesskey="u" rel="up">Coding style</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Variables-1"></a>
<h3 class="section">2.3 Variables</h3>

<p>The rule is mostly the same as functions, as noted above. If a variable is global, its name must be prefixed with grub_ and must consist of only small letters. If the variable belongs to a specific function module, the name must also be prefixed with the module name. For example, if a function is for dynamic loading, its name is prefixed with grub_dl_. If a variable is for ELF but not for all dynamic loading systems, its name is prefixed with grub_dl_elf_.
</p>
<p>After a prefix, a variable name must start with a noun or an adjective (such as name or long) and it should end with a noun. Some kind of abbreviation is permitted, as long as it wouldn&rsquo;t make code less readable (e.g. i18n).
</p>
<p>If a variable is global in the scope of a single file (i.e. it is declared with static), its name may not start with any prefix. It must start with a noun or an adjective.
</p>
<p>If a variable is local, you may choose any shorter name, as long as it wouldn&rsquo;t make code less readable (e.g. i).
</p>
<hr>
<a name="Types"></a>
<div class="header">
<p>
Next: <a href="#Macros" accesskey="n" rel="next">Macros</a>, Previous: <a href="#Variables" accesskey="p" rel="prev">Variables</a>, Up: <a href="#Coding-style" accesskey="u" rel="up">Coding style</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Types-1"></a>
<h3 class="section">2.4 Types</h3>

<p>The name of a type must be prefixed with grub_ and must consist of only small letters. If the type belongs to a specific function module, the name must also be prefixed with the module name. For example, if a type is for OS loaders, its name is prefixed with grub_loader_. If a type is for Multiboot but not for all OS loaders, its name is prefixed with grub_loader_linux_.
</p>
<p>The name must be suffixed with _t, to emphasize the fact that it is a type but not a variable or a function.
</p>
<hr>
<a name="Macros"></a>
<div class="header">
<p>
Next: <a href="#Comments" accesskey="n" rel="next">Comments</a>, Previous: <a href="#Types" accesskey="p" rel="prev">Types</a>, Up: <a href="#Coding-style" accesskey="u" rel="up">Coding style</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Macros-1"></a>
<h3 class="section">2.5 Macros</h3>

<p>If a macro is global, its name must be prefixed with GRUB_ and must consist of only large letters. Other rules are the same as functions or variables, depending on whether a macro is used like a function or a variable.
</p>
<hr>
<a name="Comments"></a>
<div class="header">
<p>
Next: <a href="#Multi_002dLine-Comments" accesskey="n" rel="next">Multi-Line Comments</a>, Previous: <a href="#Macros" accesskey="p" rel="prev">Macros</a>, Up: <a href="#Coding-style" accesskey="u" rel="up">Coding style</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Comments-1"></a>
<h3 class="section">2.6 Comments</h3>

<p>All comments shall be C-style comments, of the form &lsquo;<samp>/* &hellip; */</samp>&rsquo;.
</p>
<p>Comments shall be placed only on a line by themselves.  They shall not be placed together with code, variable declarations, or other non-comment entities.  A comment should be placed immediately preceding the entity it describes.
</p>
<p>Acceptable:
</p><div class="example">
<pre class="example">/* The page # that is the front buffer.  */
int displayed_page;
/* The page # that is the back buffer.  */
int render_page;
</pre></div>

<p>Unacceptable:
</p><div class="example">
<pre class="example">int displayed_page;           /* The page # that is the front buffer. */
int render_page;              /* The page # that is the back buffer. */
</pre></div>

<hr>
<a name="Multi_002dLine-Comments"></a>
<div class="header">
<p>
Previous: <a href="#Comments" accesskey="p" rel="prev">Comments</a>, Up: <a href="#Coding-style" accesskey="u" rel="up">Coding style</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Multi_002dLine-Comments-1"></a>
<h3 class="section">2.7 Multi-Line Comments</h3>

<p>Comments spanning multiple lines shall be formatted with all lines after the first aligned with the first line.  
</p>
<p>Asterisk characters should not be repeated a the start of each subsequent line.
</p>
<p>Acceptable:
</p><div class="example">
<pre class="example">/* This is a comment
   which spans multiple lines.
   It is long.  */
</pre></div>

<p>Unacceptable:
</p><div class="example">
<pre class="example">/*
 * This is a comment
 * which spans multiple lines.
 * It is long. */
</pre></div>

<p>The opening &lsquo;<samp>/*</samp>&rsquo; and closing &lsquo;<samp>*/</samp>&rsquo; should be placed together on a line with text.
</p>
<hr>
<a name="Finding-your-way-around"></a>
<div class="header">
<p>
Next: <a href="#Contributing-Changes" accesskey="n" rel="next">Contributing Changes</a>, Previous: <a href="#Coding-style" accesskey="p" rel="prev">Coding style</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Finding-your-way-around-1"></a>
<h2 class="chapter">3 Finding your way around</h2>

<p>Here is a brief map of the GRUB code base.
</p>
<p>GRUB uses Autoconf and Automake, with most of the Automake input generated
by a Python script.  The top-level build rules are in <samp>configure.ac</samp>,
<samp>grub-core/Makefile.core.def</samp>, and <samp>Makefile.util.def</samp>.  Each
block in a <samp>*.def</samp> file represents a build target, and specifies the
source files used to build it on various platforms.  The <samp>*.def</samp> files
are processed into Automake input by <samp>gentpl.py</samp> (which you only need
to look at if you are extending the build system).  If you are adding a new
module which follows an existing pattern, such as a new command or a new
filesystem implementation, it is usually easiest to grep
<samp>grub-core/Makefile.core.def</samp> and <samp>Makefile.util.def</samp> for an
existing example of that pattern to find out where it should be added.
</p>
<p>In general, code that may be run at boot time is in a subdirectory of
<samp>grub-core</samp>, while code that is only run from within a full operating
system is in a subdirectory of the top level.
</p>
<p>Low-level boot code, such as the MBR implementation on PC BIOS systems, is
in the <samp>grub-core/boot/</samp> directory.
</p>
<p>The GRUB kernel is in <samp>grub-core/kern/</samp>.  This contains core facilities
such as the device, disk, and file frameworks, environment variable
handling, list processing, and so on.  The kernel should contain enough to
get up to a rescue prompt.  Header files for kernel facilities, among
others, are in <samp>include/</samp>.
</p>
<p>Terminal implementations are in <samp>grub-core/term/</samp>.
</p>
<p>Disk access code is spread across <samp>grub-core/disk/</samp> (for accessing the
disk devices themselves), <samp>grub-core/partmap/</samp> (for interpreting
partition table data), and <samp>grub-core/fs/</samp> (for accessing filesystems).
Note that, with the odd specialised exception, GRUB only contains code to
<em>read</em> from filesystems and tries to avoid containing any code to
<em>write</em> to filesystems; this lets us confidently assure users that GRUB
cannot be responsible for filesystem corruption.
</p>
<p>PCI and USB bus handling is in <samp>grub-core/bus/</samp>.
</p>
<p>Video handling code is in <samp>grub-core/video/</samp>.  The graphical menu
system uses this heavily, but is in a separate directory,
<samp>grub-core/gfxmenu/</samp>.
</p>
<p>Most commands are implemented by files in <samp>grub-core/commands/</samp>, with
the following exceptions:
</p>
<ul>
<li> A few core commands live in <samp>grub-core/kern/corecmd.c</samp>.

</li><li> Commands related to normal mode live under <samp>grub-core/normal/</samp>.

</li><li> Commands that load and boot kernels live under <samp>grub-core/loader/</samp>.

</li><li> The &lsquo;<samp>loopback</samp>&rsquo; command is really a disk device, and so lives in
<samp>grub-core/disk/loopback.c</samp>.

</li><li> The &lsquo;<samp>gettext</samp>&rsquo; command lives under <samp>grub-core/gettext/</samp>.

</li><li> The &lsquo;<samp>loadfont</samp>&rsquo; and &lsquo;<samp>lsfonts</samp>&rsquo; commands live under
<samp>grub-core/font/</samp>.

</li><li> The &lsquo;<samp>serial</samp>&rsquo;, &lsquo;<samp>terminfo</samp>&rsquo;, and &lsquo;<samp>background_image</samp>&rsquo; commands
live under <samp>grub-core/term/</samp>.

</li><li> The &lsquo;<samp>efiemu_*</samp>&rsquo; commands live under <samp>grub-core/efiemu/</samp>.

</li><li> OS-dependent code should be under <samp>grub-core/osdep/</samp>

</li><li> Utility programs meant to be run from a full operating system
(except OS-dependent code mentioned previously) are in <samp>util/</samp>.

</li></ul>

<p>There are a few other special-purpose exceptions; grep for them if they
matter to you.
</p>
<hr>
<a name="Contributing-Changes"></a>
<div class="header">
<p>
Next: <a href="#Porting" accesskey="n" rel="next">Porting</a>, Previous: <a href="#Finding-your-way-around" accesskey="p" rel="prev">Finding your way around</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Contributing-changes"></a>
<h2 class="chapter">4 Contributing changes</h2>

<p>Contributing changes to GRUB 2 is welcomed activity. However we have a
bit of control what kind of changes will be accepted to GRUB 2.
Therefore it is important to discuss your changes on grub-devel mailing list
(see MailingLists). On this page there are some basic details on the
development process and activities.
</p>
<p>First of all you should come up with the idea yourself what you want to
contribute. If you do not have that beforehand you are advised to study this
manual and try GRUB 2 out to see what you think is missing from there.
</p>
<p>Here are additional pointers:
</p><ul>
<li> <a href="https://savannah.gnu.org/task/?group=grub GRUB's Task Tracker">https://savannah.gnu.org/task/?group=grub GRUB's Task Tracker</a>
</li><li> <a href="https://savannah.gnu.org/bugs/?group=grub GRUB's Bug Tracker">https://savannah.gnu.org/bugs/?group=grub GRUB's Bug Tracker</a>
</li></ul>

<p>If you intended to make changes to GRUB Legacy (&lt;=0.97) those are not accepted
anymore.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Getting-started" accesskey="1">Getting started</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Typical-Developer-Experience" accesskey="2">Typical Developer Experience</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#When-you-are-approved-for-write-access-to-project_0027s-files" accesskey="3">When you are approved for write access to project's files</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Getting-started"></a>
<div class="header">
<p>
Next: <a href="#Typical-Developer-Experience" accesskey="n" rel="next">Typical Developer Experience</a>, Up: <a href="#Contributing-Changes" accesskey="u" rel="up">Contributing Changes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Getting-started-1"></a>
<h3 class="section">4.1 Getting started</h3>

<ul>
<li> Always use latest GRUB 2 source code. So get that first.

<p>For developers it is recommended always to use the newest development version of GRUB 2. If development takes a long period of time, please remember to keep in sync with newest developments regularly so it is much easier to integrate your change in the future. GRUB 2 is being developed in a GIT repository.
</p>
<p>Please check Savannah&rsquo;s GRUB project page for details how to get newest git:
<a href="https://savannah.gnu.org/git/?group=grub">GRUB 2 git Repository</a>
</p>
</li><li> Compile it and try it out.

<p>It is always good idea to first see that things work somehow and after that
to start to implement new features or develop fixes to bugs.
</p>
</li><li> Study the code.

<p>There are sometimes odd ways to do things in GRUB 2 code base.
This is mainly related to limited environment where GRUB 2 is being executed.
You usually do not need to understand it all so it is better to only try to
look at places that relates to your work. Please do not hesitate to ask for
help if there is something that you do not understand.
</p>
</li><li> Develop a new feature.

<p>Now that you know what to do and how it should work in GRUB 2 code base, please
be free to develop it. If you have not so far announced your idea on grub-devel
mailing list, please do it now. This is to make sure you are not wasting your
time working on the solution that will not be integrated to GRUB 2 code base.
</p>
<p>You might want to study our coding style before starting development so you
do not need to change much of the code when your patch is being reviewed.
(see <a href="#Coding-style">Coding style</a>)
</p>
<p>For every accepted patch there has to exist a ChangeLog entry. Our ChangeLog
consist of changes within source code and are not describing about what the
change logically does. Please see examples from previous entries.
</p>
<p>Also remember that GRUB 2 is licensed under GPLv3 license and that usually
means that you are not allowed to copy pieces of code from other projects.
Even if the source project&rsquo;s license would be compatible with GPLv3, please
discuss it beforehand on grub-devel mailing list.
</p>
</li><li> Test your change.

<p>Test that your change works properly. Try it out a couple of times, preferably on different systems, and try to find problems with it.
</p>
</li><li> Publish your change.

<p>When you are happy with your change, first make sure it is compilable with
latest development version of GRUB 2. After that please send a patch to
grub-devel for review. Please describe in your email why you made the change,
what it changes and so on. Please be prepared to receive even discouraging
comments about your patch. There is usually at least something that needs
to be improved in every patch.
</p>
<p>Please use unified diff to make your patch (good match of arguments for diff is &lsquo;<samp>-pruN</samp>&rsquo;).
</p>
</li><li> Respond to received feedback.

<p>If you are asked to modify your patch, please do that and resubmit it for
review. If your change is large you are required to submit a copyright
agreement to FSF. Please keep in mind that if you are asked to submit
for copyright agreement, process can take some time and is mandatory
in order to get your changes integrated.
</p>
<p>If you are not on grub-devel to respond to questions, most likely your patch
will not be accepted. Also if problems arise from your changes later on,
it would be preferable that you also fix the problem. So stay around
for a while.
</p>
</li><li> Your patch is accepted.

<p>Good job! Your patch will now be integrated into GRUB 2 mainline, and if it didn&rsquo;t break anything it will be publicly available in the next release.
</p>
<p>Now you are welcome to do further improvements :)
</p></li></ul>

<hr>
<a name="Typical-Developer-Experience"></a>
<div class="header">
<p>
Next: <a href="#When-you-are-approved-for-write-access-to-project_0027s-files" accesskey="n" rel="next">When you are approved for write access to project's files</a>, Previous: <a href="#Getting-started" accesskey="p" rel="prev">Getting started</a>, Up: <a href="#Contributing-Changes" accesskey="u" rel="up">Contributing Changes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Typical-Developer-Experience-1"></a>
<h3 class="section">4.2 Typical Developer Experience</h3>

<p>The typical experience for a developer in this project is the following:
</p>
<ol>
<li> You find yourself wanting to do something (e.g. fixing a bug).
</li><li> You show some result in the mailing list or the IRC.
</li><li> You are getting to be known to other developers.
</li><li> You accumulate significant amount of contribution, so copyright assignment is processed.
</li><li> You are free to check in your changes on your own, legally speaking.
</li></ol>

<p>At this point, it is rather annoying that you ought to ask somebody else every
change to be checked in. For efficiency, it is far better, if you can commit
it yourself. Therefore, our policy is to give you the write permission to our
official repository, once you have shown your skill and will,
and the FSF clerks have dealt with your copyright assignment.
</p>
<hr>
<a name="When-you-are-approved-for-write-access-to-project_0027s-files"></a>
<div class="header">
<p>
Previous: <a href="#Typical-Developer-Experience" accesskey="p" rel="prev">Typical Developer Experience</a>, Up: <a href="#Contributing-Changes" accesskey="u" rel="up">Contributing Changes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="When-you-are-approved-for-write-access-to-project_0027s-files-1"></a>
<h3 class="section">4.3 When you are approved for write access to project&rsquo;s files</h3>

<p>As you might know, GRUB is hosted on
<a href="https://savannah.gnu.org/projects/grub Savannah">https://savannah.gnu.org/projects/grub Savannah</a>, thus the membership
is managed by Savannah. This means that, if you want to be a member of this
project:
</p>
<ol>
<li> You need to create your own account on Savannah.
</li><li> You can submit &ldquo;Request for Inclusion&rdquo; from &ldquo;My Groups&rdquo; on Savannah.
</li></ol>

<p>Then, one of the admins can approve your request, and you will be a member.
If you don&rsquo;t want to use the Savannah interface to submit a request, you can
simply notify the admins by email or something else, alternatively. But you
still need to create an account beforehand.
</p>
<p>NOTE: we sometimes receive a &ldquo;Request for Inclusion&rdquo; from an unknown person.
In this case, the request would be just discarded, since it is too dangerous
to allow a stranger to be a member, which automatically gives him a commit
right to the repository, both for a legal reason and for a technical reason. 
</p>
<p>If your intention is to just get started, please do not submit a inclusion
request. Instead, please subscribe to the mailing list, and communicate first
(e.g. sending a patch, asking a question, commenting on another message...).
</p>
<hr>
<a name="Porting"></a>
<div class="header">
<p>
Next: <a href="#Error-Handling" accesskey="n" rel="next">Error Handling</a>, Previous: <a href="#Contributing-Changes" accesskey="p" rel="prev">Contributing Changes</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Porting-1"></a>
<h2 class="chapter">5 Porting</h2>

<p>GRUB2 is designed to be easily portable accross platforms. But because of the
nature of bootloader every new port must be done separately. Here is how I did
MIPS (loongson and ARC) and Xen ports. Note than this is more of suggestions,
not absolute truth.
</p>
<p>First of all grab any architecture specifications you can find in public
(please avoid NDA).
</p>
<p>First stage is &ldquo;Hello world&rdquo;. I&rsquo;ve done it outside of GRUB for simplicity.
Your task is to have a small program which is loadable as bootloader and
clearly shows its presence to you. If you have easily accessible console
you can just print a message. If you have a mapped framebuffer you know address
of, you can draw a square. If you have a debug facility, just hanging without
crashing might be enough. For the first stage you can choose to load the
bootloader across the network since format for network image is often easier
than for local boot and it skips the need of small intermediary stages and
nvram handling. Additionally you can often have a good idea of the needed
format by running &ldquo;file&rdquo; on any netbootable executable for given platform.
</p>
<p>This program should probably have 2 parts: an assembler and C one. Assembler one
handles BSS cleaning and other needed setup (on some platforms you may need
to switch modes or copy the executable to its definitive position). So your code
may look like (x86 assembly for illustration purposes)
</p>
<div class="example">
<pre class="example">        .globl _start
_start:
	movl	$_bss_start, %edi
	movl	$_end, %ecx
	subl	%edi, %ecx
	xorl	%eax, %eax
	cld
	rep
	stosb
        call main
</pre></div>

static const char msg[] = &quot;Hello, world&quot;;

void
putchar (int c)
{
  ...
}

void
main (void)
{
  const char *ptr = msg;
  while (*ptr)
    putchar (*ptr++);
  while (1);
}
</pre></div>

<p>Sometimes you need a third file: assembly stubs for ABI-compatibility.
</p>
<p>Once this file is functional it&rsquo;s time to move it into GRUB2. The startup
assembly file goes to grub-core/kern/$cpu/$platform/startup.S. You should also
include grub/symbol.h and replace call to entry point with call to
EXT_C(grub_main). The C file goes to grub-core/kern/$cpu/$platform/init.c
and its entry point is renamed to void grub_machine_init (void). Keep final
infinite loop for now. Stubs file if any goes to
grub-core/kern/$cpu/$platform/callwrap.S. Sometimes either $cpu or $platform
is dropped if file is used on several cpus respectivelyplatforms.
Check those locations if they already have what you&rsquo;re looking for.
</p>
<p>Then modify in configure.ac the following parts:
</p>
<p>CPU names:
</p>
<div class="example">
<pre class="example">case &quot;$target_cpu&quot; in
  i[[3456]]86)	target_cpu=i386 ;;
  amd64)	target_cpu=x86_64 ;;
  sparc)	target_cpu=sparc64 ;;
  s390x)	target_cpu=s390 ;;
  ...
esac
</pre></div>

<p>Sometimes CPU have additional architecture names which don&rsquo;t influence booting.
You might want to have some canonical name to avoid having bunch of identical
platforms with different names.
</p>
<p>NOTE: it doesn&rsquo;t influence compile optimisations which depend solely on
chosen compiler and compile options.
</p>
<div class="example">
<pre class="example">if test &quot;x$with_platform&quot; = x; then
  case &quot;$target_cpu&quot;-&quot;$target_vendor&quot; in
    i386-apple) platform=efi ;;
    i386-*) platform=pc ;;
    x86_64-apple) platform=efi ;;
    x86_64-*) platform=pc ;;
    powerpc-*) platform=ieee1275 ;;
    ...
  esac
else
  ...
fi
</pre></div>

<p>This part deals with guessing the platform from CPU and vendor. Sometimes you
need to use 32-bit mode for booting even if OS runs in 64-bit one. If so add
your platform to:
</p>
<div class="example">
<pre class="example">case &quot;$target_cpu&quot;-&quot;$platform&quot; in
  x86_64-efi) ;;
  x86_64-emu) ;;
  x86_64-*) target_cpu=i386 ;;
  powerpc64-ieee1275) target_cpu=powerpc ;;
esac
</pre></div>

<p>Add your platform to the list of supported ones:
</p>
<div class="example">
<pre class="example">case &quot;$target_cpu&quot;-&quot;$platform&quot; in
  i386-efi) ;;
  x86_64-efi) ;;
  i386-pc) ;;
  i386-multiboot) ;;
  i386-coreboot) ;;
  ...
esac
</pre></div>

<p>If explicit -m32 or -m64 is needed add it to:
</p>
<div class="example">
<pre class="example">case &quot;$target_cpu&quot; in
  i386 | powerpc) target_m32=1 ;;
  x86_64 | sparc64) target_m64=1 ;;
esac
</pre></div>

<p>Finally you need to add a conditional to the following block:
</p>
<div class="example">
<pre class="example">AM_CONDITIONAL([COND_mips_arc], [test x$target_cpu = xmips -a x$platform = xarc])
AM_CONDITIONAL([COND_sparc64_ieee1275], [test x$target_cpu = xsparc64 -a x$platform = xieee1275])
AM_CONDITIONAL([COND_powerpc_ieee1275], [test x$target_cpu = xpowerpc -a x$platform = xieee1275])
</pre></div>

<p>Next stop is gentpl.py. You need to add your platform to the list of supported
ones (sorry that this list is duplicated):
</p>
<div class="example">
<pre class="example">GRUB_PLATFORMS = [ &quot;emu&quot;, &quot;i386_pc&quot;, &quot;i386_efi&quot;, &quot;i386_qemu&quot;, &quot;i386_coreboot&quot;,
                   &quot;i386_multiboot&quot;, &quot;i386_ieee1275&quot;, &quot;x86_64_efi&quot;,
                   &quot;mips_loongson&quot;, &quot;sparc64_ieee1275&quot;,
                   &quot;powerpc_ieee1275&quot;, &quot;mips_arc&quot;, &quot;ia64_efi&quot;,
                   &quot;mips_qemu_mips&quot;, &quot;s390_mainframe&quot; ]
</pre></div>

<p>You may also want already to add new platform to one or several of available
groups. In particular we always have a group for each CPU even when only
one platform for given CPU is available.
</p>
<p>Then comes grub-core/Makefile.core.def. In the block &ldquo;kernel&rdquo; you&rsquo;ll need
to define ldflags for your platform ($cpu_$platform_ldflags). You also need to
declare startup asm file ($cpu_$platform_startup) as well as any other files
(e.g. init.c and callwrap.S) (e.g. $cpu_$platform = kern/$cpu/$platform/init.c).
At this stage you will also need to add dummy dl.c and cache.S with functions
grub_err_t grub_arch_dl_check_header (void *ehdr), grub_err_t
grub_arch_dl_relocate_symbols (grub_dl_t mod, void *ehdr) (dl.c), grub_uint32_t
grub_arch_dl_min_alignment (void), and void grub_arch_sync_caches (void
*address, grub_size_t len) (cache.S). They won&rsquo;t be used for now.
</p>
<p>You will need to create directory include/$cpu/$platform and a file
include/$cpu/types.h. The later folowing this template:
</p>
<div class="example">
<pre class="example">#ifndef GRUB_TYPES_CPU_HEADER
#define GRUB_TYPES_CPU_HEADER	1

/* The size of void *.  */
#define GRUB_TARGET_SIZEOF_VOID_P	4

/* The size of long.  */
#define GRUB_TARGET_SIZEOF_LONG		4

/* mycpu is big-endian.  */
#define GRUB_TARGET_WORDS_BIGENDIAN	1
/* Alternatively: mycpu is little-endian.  */
#undef GRUB_TARGET_WORDS_BIGENDIAN

#endif /* ! GRUB_TYPES_CPU_HEADER */
</pre></div>

<p>You will also need to add a dummy file to datetime and setjmp modules to
avoid any of it having no files. It can be just completely empty at this stage.
</p>
<p>You&rsquo;ll need to make grub-mkimage.c (util/grub_mkimage.c) aware of the needed
format. For most commonly used formats like ELF, PE, aout or raw the support
is already present and you&rsquo;ll need to make it follow the existant code paths
for your platform adding adjustments if necessary. When done compile:
</p>
<div class="example">
<pre class="example">./autogen.sh
./configure --target=$cpu --with-platform=$platform TARGET_CC=.. OBJCOPY=... STRIP=...
make &gt; /dev/null
</pre></div>

<p>And create image
</p>
<div class="example">
<pre class="example">./grub-mkimage -d grub-core -O $format_id -o test.img
</pre></div>

<p>And it&rsquo;s time to test your test.img.
</p>
<p>If it works next stage is to have heap, console and timer.
</p>
<p>To have the heap working you need to determine which regions are suitable for
heap usage, allocate them from firmware and map (if applicable). Then call
grub_mm_init_region (vois *start, grub_size_t s) for every of this region.
As a shortcut for early port you can allocate right after _end or have
a big static array for heap. If you do you&rsquo;ll probably need to come back to
this later. As for output console you should distinguish between an array of
text, terminfo or graphics-based console. Many of real-world examples don&rsquo;t
fit perfectly into any of these categories but one of the models is easier
to be used as base. In second and third case you should add your platform to 
terminfokernel respectively videoinkernel group. A good example of array of
text is i386-pc (kern/i386/pc/init.c and term/i386/pc/console.c).
Of terminfo is ieee1275 (kern/ieee1275/init.c and term/ieee1275/console.c).
Of video is loongson (kern/mips/loongson/init.c). Note that terminfo has
to be inited in 2 stages: one before (to get at least rudimentary console
as early as possible) and another after the heap (to get full-featured console).
For the input there are string of keys, terminfo and direct hardware. For string
of keys look at i386-pc (same files), for termino ieee1275 (same files) and for
hardware loongson (kern/mips/loongson/init.c and term/at_keyboard.c).
</p>
<p>For the timer you&rsquo;ll need to call grub_install_get_time_ms (...) with as sole
argument a function returning a grub_uint64_t of a number of milliseconds
elapsed since arbitrary point in the past.
</p>
<p>Once these steps accomplished you can remove the inifinite loop and you should
be able to get to the minimal console. Next step is to have module loading
working. For this you&rsquo;ll need to fill kern/$cpu/dl.c and kern/$cpu/cache.S
with real handling of relocations and respectively the real sync of I and D
caches. Also you&rsquo;ll need to decide where in the image to store the modules.
Usual way is to have it concatenated at the end. In this case you&rsquo;ll need to
modify startup.S to copy modules out of bss to let&rsquo;s say ALIGN_UP (_end, 8)
before cleaning out bss. You&rsquo;ll probably find useful to add total_module_size
field to startup.S. In init.c you need to set grub_modbase to the address
where modules can be found. You may need grub_modules_get_end () to avoid
declaring the space occupied by modules as usable for heap. You can test modules
with:
</p>
<div class="example">
<pre class="example">./grub-mkimage -d grub-core -O $format_id -o test.img hello
</pre></div>

<p>and then running &ldquo;hello&rdquo; in the shell.
</p>
<p>Once this works, you should think of implementing disk access. Look around
disk/ for examples.
</p>
<p>Then, very importantly, you probably need to implement the actual loader
(examples available in loader/)
</p>
<p>Last step to have minimally usable port is to add support to grub-install to
put GRUB in a place where firmware or platform will pick it up.
</p>
<p>Next steps are: filling datetime.c, setjmp.S, network (net/drivers),
video (video/), halt (lib/), reboot (lib/).
</p>
<p>Please add your platform to Platform limitations and Supported kernels chapter
in user documentation and mention any steps you skipped which result in reduced
features or performance. Here is the quick checklist of features. Some of them
are less important than others and skipping them is completely ok, just needs
to be mentioned in user documentation.
</p>
<p>Checklist:
</p><ul>
<li> Is heap big enough?
</li><li> Which charset is supported by console?
</li><li> Does platform have disk driver?
</li><li> Do you have network card support?
</li><li> Are you able to retrieve datetime (with date)?
</li><li> Are you able to set datetime (with date)?
</li><li> Is serial supported?
</li><li> Do you have direct disk support?
</li><li> Do you have direct keyboard support?
</li><li> Do you have USB support?
</li><li> Do you support loading through network?
</li><li> Do you support loading from disk?
</li><li> Do you support chainloading?
</li><li> Do you support network chainloading?
</li><li> Does cpuid command supports checking all
CPU features that the user might want conditionalise on
(64-bit mode, hypervisor,...)
</li><li> Do you support hints? How reliable are they?
</li><li> Does platform have ACPI? If so do &ldquo;acpi&rdquo; and &ldquo;lsacpi&rdquo; modules work?
</li><li> Do any of platform-specific operations mentioned in the relevant section of
user manual makes sense on your platform?
</li><li> Does your platform support PCI? If so is there an appropriate driver for
GRUB?
</li><li> Do you support badram?
</li></ul>

<hr>
<a name="Error-Handling"></a>
<div class="header">
<p>
Next: <a href="#Stack-and-heap-size" accesskey="n" rel="next">Stack and heap size</a>, Previous: <a href="#Porting" accesskey="p" rel="prev">Porting</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Error-Handling-1"></a>
<h2 class="chapter">6 Error Handling</h2>

<p>Error handling in GRUB 2 is based on exception handling model. As C language
doesn&rsquo;t directly support exceptions, exception handling behavior is emulated
in software. 
</p>
<p>When exception is raised, function must return to calling function. If calling
function does not provide handling of the exception it must return back to its
calling function and so on, until exception is handled. If exception is not
handled before prompt is displayed, error message will be shown to user.
</p>
<p>Exception information is stored on <code>grub_errno</code> global variable. If
<code>grub_errno</code> variable contains value <code>GRUB_ERR_NONE</code>, there is no active
exception and application can continue normal processing. When <code>grub_errno</code> has
other value, it is required that application code either handles this error or
returns instantly to caller. If function is with return type <code>grub_err_t</code> is
about to return <code>GRUB_ERR_NONE</code>, it should not set <code>grub_errno</code> to that
value. Only set <code>grub_errno</code> in cases where there is error situation. 
</p>
<p>Simple exception forwarder.
</p><div class="example">
<pre class="example">grub_err_t
forwarding_example (void)
{
  /* Call function that might cause exception.  */
  foobar ();

/* No special exception handler, just forward possible exceptions.  */
  if (grub_errno != GRUB_ERR_NONE)
    {
      return grub_errno;
    }

/* All is OK, do more processing.  */

/* Return OK signal, to caller.  */
  return GRUB_ERR_NONE;
}
</pre></div>

<p>Error reporting has two components, the actual error code (of type
<code>grub_err_t</code>) and textual message that will be displayed to user. List of
valid error codes is listed in header file <samp>include/grub/err.h</samp>. Textual
error message can contain any textual data. At time of writing, error message
can contain up to 256 characters (including terminating NUL). To ease error
reporting there is a helper function <code>grub_error</code> that allows easier
formatting of error messages and should be used instead of writing directly to
global variables.
</p>
<p>Example of error reporting.
</p><div class="example">
<pre class="example">grub_err_t
failing_example ()
{
  return grub_error (GRUB_ERR_FILE_NOT_FOUND, 
                     &quot;Failed to read %s, tried %d times.&quot;,
                     &quot;test.txt&quot;,
                     10);
}
</pre></div>

<p>If there is a special reason that error code does not need to be taken account,
<code>grub_errno</code> can be zeroed back to <code>GRUB_ERR_NONE</code>. In cases like this all
previous error codes should have been handled correctly. This makes sure that
there are no unhandled exceptions.
</p>
<p>Example of zeroing <code>grub_errno</code>.
</p><div class="example">
<pre class="example">grub_err_t
probe_example ()
{
  /* Try to probe device type 1.  */
  probe_for_device ();
  if (grub_errno == GRUB_ERR_NONE)
    {
      /* Device type 1 was found on system.  */
      register_device ();
      return GRUB_ERR_NONE;
    }
  /* Zero out error code.  */
  grub_errno = GRUB_ERR_NONE;

/* No device type 1 found, try to probe device type 2.  */
  probe_for_device2 ();
  if (grub_errno == GRUB_ERR_NONE)
    {
      /* Device type 2 was found on system.  */
      register_device2 ();
      return GRUB_ERR_NONE;
    }
  /* Zero out error code.  */
  grub_errno = GRUB_ERR_NONE;

/* Return custom error message.  */
  return grub_error (GRUB_ERR_UNKNOWN_DEVICE, &quot;No device type 1 or 2 found.&quot;);
}
</pre></div>

<p>Some times there is a need to continue processing even if there is a error
state in application. In situations like this, there is a needed to save old
error state and then call other functions that might fail. To aid in this,
there is a error stack implemented. Error state can be pushed to error stack
by calling function <code>grub_error_push ()</code>. When processing has been completed,
<code>grub_error_pop ()</code> can be used to pop error state from stack. Error stack
contains predefined amount of error stack items. Error stack is protected for
overflow and marks these situations so overflow error does not get unseen.
If there is no space available to store error message, it is simply discarded
and overflow will be marked as happened. When overflow happens, it most likely
will corrupt error stack consistency as for pushed error there is no matching
pop, but overflow message will be shown to inform user about the situation.
Overflow message will be shown at time when prompt is about to be drawn.
</p>
<p>Example usage of error stack.
</p><div class="example">
<pre class="example">/* Save possible old error message.  */
grub_error_push ();

/* Do your stuff here.  */
call_possibly_failing_function ();

if (grub_errno != GRUB_ERR_NONE)
  {
    /* Inform rest of the code that there is error (grub_errno
       is set). There is no pop here as we want both error states 
       to be displayed.  */
    return;
  }

/* Restore old error state by popping previous item from stack. */
grub_error_pop ();
</pre></div>

<hr>
<a name="Stack-and-heap-size"></a>
<div class="header">
<p>
Next: <a href="#BIOS-port-memory-map" accesskey="n" rel="next">BIOS port memory map</a>, Previous: <a href="#Error-Handling" accesskey="p" rel="prev">Error Handling</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Stack-and-heap-size-1"></a>
<h2 class="chapter">7 Stack and heap size</h2>

<p>On emu stack and heap are just normal host OS stack and heap. Stack is typically
8 MiB although it&rsquo;s OS-dependent.
</p>
<p>On i386-pc, i386-coreboot, i386-qemu and i386-multiboot the stack is 60KiB.
All available space between 1MiB and 4GiB marks is part of heap.
</p>
<p>On *-xen stack is 4MiB. If compiled for x86-64 with GCC 4.4 or later adressable
space is unlimited. When compiled for x86-64 with older GCC version adressable
space is limited to 2GiB. When compiling for i386 adressable space is limited
to 4GiB. All adressable pages except the ones for stack, GRUB binary, special
pages and page table are in the heap.
</p>
<p>On *-efi GRUB uses same stack as EFI. If compiled for x86-64 with GCC 4.4 or
later adressable space is unlimited. When compiled for x86-64 with older GCC
version adressable space is limited to 2GiB. For all other platforms adressable
space is limited to 4GiB. GRUB allocates pages from EFI for its heap, at most
1.6 GiB.
</p>
<p>On i386-ieee1275 and powerpc-ieee1275 GRUB uses same stack as IEEE1275.
</p>
<p>On i386-ieee1275, GRUB allocates at most 32MiB for its heap. On
powerpc-ieee1275, GRUB allocates up to 1GiB.
</p>
<p>On sparc64-ieee1275 stack is 256KiB and heap is 2MiB.
</p>
<p>On mips(el)-qemu_mips and mipsel-loongson stack is 2MiB (everything below
GRUB image) and everything above GRUB image (from 2MiB + kernel size)
until 256MiB is part of heap.
</p>
<p>On mips-arc stack is 2MiB (everything below GRUB image) and everything above
GRUB image(from 2MiB + kernel size) until 128MiB is part of heap.
</p>
<p>On mipsel-arc stack is 2MiB (everything below GRUB image which is not part
of ARC) and everything above GRUB image (from 7MiB + kernel size)
until 256MiB is part of heap.
</p>
<p>On arm-uboot stack is 256KiB and heap is 2MiB.
</p>
<p>In short:
</p>
<table>
<thead><tr><th width="15%">Platform</th><th width="25%">Stack</th><th width="50%">Heap</th></tr></thead>
<tr><td width="15%">emu</td><td width="25%">8 MiB</td><td width="50%">?</td></tr>
<tr><td width="15%">i386-pc</td><td width="25%">60 KiB</td><td width="50%">&lt; 4 GiB</td></tr>
<tr><td width="15%">i386-coreboot</td><td width="25%">60 KiB</td><td width="50%">&lt; 4 GiB</td></tr>
<tr><td width="15%">i386-multiboot</td><td width="25%">60 KiB</td><td width="50%">&lt; 4 GiB</td></tr>
<tr><td width="15%">i386-qemu</td><td width="25%">60 KiB</td><td width="50%">&lt; 4 GiB</td></tr>
<tr><td width="15%">*-efi</td><td width="25%">?</td><td width="50%">&lt; 1.6 GiB</td></tr>
<tr><td width="15%">i386-ieee1275</td><td width="25%">?</td><td width="50%">&lt; 32 MiB</td></tr>
<tr><td width="15%">powerpc-ieee1275</td><td width="25%">?</td><td width="50%">&lt; 1 GiB</td></tr>
<tr><td width="15%">sparc64-ieee1275</td><td width="25%">256KiB</td><td width="50%">2 MiB</td></tr>
<tr><td width="15%">arm-uboot</td><td width="25%">256KiB</td><td width="50%">2 MiB</td></tr>
<tr><td width="15%">mips(el)-qemu_mips</td><td width="25%">2MiB</td><td width="50%">253 MiB</td></tr>
<tr><td width="15%">mipsel-loongson</td><td width="25%">2MiB</td><td width="50%">253 MiB</td></tr>
<tr><td width="15%">mips-arc</td><td width="25%">2MiB</td><td width="50%">125 MiB</td></tr>
<tr><td width="15%">mipsel-arc</td><td width="25%">2MiB</td><td width="50%">248 MiB</td></tr>
<tr><td width="15%">x86_64-xen (GCC &gt;= 4.4)</td><td width="25%">4MiB</td><td width="50%">unlimited</td></tr>
<tr><td width="15%">x86_64-xen (GCC &lt; 4.4)</td><td width="25%">4MiB</td><td width="50%">&lt; 2GiB</td></tr>
<tr><td width="15%">i386-xen</td><td width="25%">4MiB</td><td width="50%">&lt; 4GiB</td></tr>
</table>

<hr>
<a name="BIOS-port-memory-map"></a>
<div class="header">
<p>
Next: <a href="#Video-Subsystem" accesskey="n" rel="next">Video Subsystem</a>, Previous: <a href="#Stack-and-heap-size" accesskey="p" rel="prev">Stack and heap size</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="BIOS-port-memory-map-1"></a>
<h2 class="chapter">8 BIOS port memory map</h2>

<table>
<thead><tr><th width="15%">Start</th><th width="25%">End</th><th width="50%">Usage</th></tr></thead>
<tr><td width="15%">0</td><td width="25%">0x1000 - 1</td><td width="50%">BIOS and real mode interrupts</td></tr>
<tr><td width="15%">0x07BE</td><td width="25%">0x07FF</td><td width="50%">Partition table passed to another boot loader</td></tr>
<tr><td width="15%">?</td><td width="25%">0x2000 - 1</td><td width="50%">Real mode stack</td></tr>
<tr><td width="15%">0x7C00</td><td width="25%">0x7D00 - 1</td><td width="50%">Boot sector</td></tr>
<tr><td width="15%">0x8000</td><td width="25%">?</td><td width="50%">GRUB kernel</td></tr>
<tr><td width="15%">0x68000</td><td width="25%">0x71000 - 1</td><td width="50%">Disk buffer</td></tr>
<tr><td width="15%">?</td><td width="25%">0x80000 - 1</td><td width="50%">Protected mode stack</td></tr>
<tr><td width="15%">?</td><td width="25%">0xA0000 - 1</td><td width="50%">Extended BIOS Data Area</td></tr>
<tr><td width="15%">0xA0000</td><td width="25%">0xC0000 - 1</td><td width="50%">Video RAM</td></tr>
<tr><td width="15%">0xC0000</td><td width="25%">0x100000 - 1</td><td width="50%">BIOS</td></tr>
<tr><td width="15%">0x100000</td><td width="25%">?</td><td width="50%">Heap and module code</td></tr>
</table>

<hr>
<a name="Video-Subsystem"></a>
<div class="header">
<p>
Next: <a href="#PFF2-Font-File-Format" accesskey="n" rel="next">PFF2 Font File Format</a>, Previous: <a href="#BIOS-port-memory-map" accesskey="p" rel="prev">BIOS port memory map</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Video-Subsystem-1"></a>
<h2 class="chapter">9 Video Subsystem</h2>
<p>This document contains specification for Video Subsystem for GRUB2.
Currently only the usage interface is described in this document.
Internal structure of how video drivers are registering and how video
driver manager works are not included here.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Video-API" accesskey="1">Video API</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Example-usage-of-Video-API" accesskey="2">Example usage of Video API</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Bitmap-API" accesskey="3">Bitmap API</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Video-API"></a>
<div class="header">
<p>
Next: <a href="#Example-usage-of-Video-API" accesskey="n" rel="next">Example usage of Video API</a>, Up: <a href="#Video-Subsystem" accesskey="u" rel="up">Video Subsystem</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Video-API-1"></a>
<h3 class="section">9.1 Video API</h3>

<a name="grub_005fvideo_005fsetup"></a>
<h4 class="subsection">9.1.1 grub_video_setup</h4>

<ul>
<li> Prototype:
<div class="example">
<pre class="example">grub_err_t
grub_video_setup (unsigned int width, unsigned int height, unsigned int mode_type);
</pre></div>
</li><li> Description:

<p>Driver will use information provided to it to select best possible video mode and switch to it. Supported values for <code>mode_type</code> are <code>GRUB_VIDEO_MODE_TYPE_INDEX_COLOR</code> for index color modes, <code>GRUB_VIDEO_MODE_TYPE_RGB</code> for direct RGB color modes and <code>GRUB_VIDEO_MODE_TYPE_DOUBLE_BUFFERED</code> for double buffering. When requesting RGB mode, highest bits per pixel mode will be selected. When requesting Index color mode, mode with highest number of colors will be selected. If all parameters are specified as zero, video adapter will try to figure out best possible mode and initialize it, platform specific differences are allowed here. If there is no mode matching request, error X will be returned. If there are no problems, function returns <code>GRUB_ERR_NONE</code>.
</p>
<p>This function also performs following task upon succesful mode switch. Active rendering target is changed to screen and viewport is maximized to allow whole screen to be used when performing graphics operations. In RGB modes, emulated palette gets 16 entries containing default values for VGA palette, other colors are defined as black. When switching to Indexed Color mode, driver may set default VGA palette to screen if the video card allows the operation.
</p>
</li></ul>

<a name="grub_005fvideo_005frestore"></a>
<h4 class="subsection">9.1.2 grub_video_restore</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_restore (void);
</pre></div>
</li><li> Description:

<p>Video subsystem will deinitialize activated video driver to restore old state of video device. This can be used to switch back to text mode.
</p></li></ul>

<a name="grub_005fvideo_005fget_005finfo"></a>
<h4 class="subsection">9.1.3 grub_video_get_info</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_get_info (struct grub_video_mode_info *mode_info);
</pre></div>
<div class="example">
<pre class="example">struct grub_video_mode_info
{
  /* Width of the screen.  */
  unsigned int width;
  /* Height of the screen.  */
  unsigned int height;
  /* Mode type bitmask.  Contains information like is it Index color or
     RGB mode.  */
  unsigned int mode_type;
  /* Bits per pixel.  */
  unsigned int bpp;
  /* Bytes per pixel.  */
  unsigned int bytes_per_pixel;
  /* Pitch of one scanline.  How many bytes there are for scanline.  */
  unsigned int pitch;
  /* In index color mode, number of colors.  In RGB mode this is 256.  */
  unsigned int number_of_colors;
  /* Optimization hint how binary data is coded.  */
  enum grub_video_blit_format blit_format;
  /* How many bits are reserved for red color.  */
  unsigned int red_mask_size;
  /* What is location of red color bits.  In Index Color mode, this is 0.  */
  unsigned int red_field_pos;
  /* How many bits are reserved for green color.  */
  unsigned int green_mask_size;
  /* What is location of green color bits.  In Index Color mode, this is 0.  */
  unsigned int green_field_pos;
  /* How many bits are reserved for blue color.  */
  unsigned int blue_mask_size;
  /* What is location of blue color bits.  In Index Color mode, this is 0.  */
  unsigned int blue_field_pos;
  /* How many bits are reserved in color.  */
  unsigned int reserved_mask_size;
  /* What is location of reserved color bits.  In Index Color mode,
     this is 0.  */
  unsigned int reserved_field_pos;
};
</pre></div>
</li><li> Description:

<p>Software developer can use this function to query properties of active rendering taget. Information provided here can be used by other parts of GRUB, like image loaders to convert loaded images to correct screen format to allow more optimized blitters to be used. If there there is no configured video driver with active screen, error <code>GRUB_ERR_BAD_DEVICE</code> is returned, otherwise <code>mode_info</code> is filled with valid information and <code>GRUB_ERR_NONE</code> is returned.
</p></li></ul>

<a name="grub_005fvideo_005fget_005fblit_005fformat"></a>
<h4 class="subsection">9.1.4 grub_video_get_blit_format</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">enum grub_video_blit_format
grub_video_get_blit_format (struct grub_video_mode_info *mode_info);
</pre></div>
<div class="example">
<pre class="example">enum grub_video_blit_format
  {
    /* Follow exactly field &amp; mask information.  */
    GRUB_VIDEO_BLIT_FORMAT_RGBA,
    /* Make optimization assumption.  */
    GRUB_VIDEO_BLIT_FORMAT_R8G8B8A8,
    /* Follow exactly field &amp; mask information.  */
    GRUB_VIDEO_BLIT_FORMAT_RGB,
    /* Make optimization assumption.  */
    GRUB_VIDEO_BLIT_FORMAT_R8G8B8,
    /* When needed, decode color or just use value as is.  */
    GRUB_VIDEO_BLIT_FORMAT_INDEXCOLOR
  };
</pre></div>
</li><li> Description:

<p>Used to query how data could be optimized to suit specified video mode. Returns exact video format type, or a generic one if there is no definition for the type. For generic formats, use <code>grub_video_get_info</code> to query video color coding settings.
</p></li></ul>

<a name="grub_005fvideo_005fset_005fpalette"></a>
<h4 class="subsection">9.1.5 grub_video_set_palette</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_set_palette (unsigned int start, unsigned int count, struct grub_video_palette_data *palette_data);
</pre></div>
<div class="example">
<pre class="example">struct grub_video_palette_data
{
    grub_uint8_t r; /* Red color value (0-255). */
    grub_uint8_t g; /* Green color value (0-255). */
    grub_uint8_t b; /* Blue color value (0-255). */
    grub_uint8_t a; /* Reserved bits value (0-255). */
};
</pre></div>
</li><li> Description:

<p>Used to setup indexed color palettes. If mode is RGB mode, colors will be set to emulated palette data. In Indexed Color modes, palettes will be set to hardware. Color values will be converted to suit requirements of the video mode. <code>start</code> will tell what hardware color index (or emulated color index) will be set to according information in first indice of <code>palette_data</code>, after that both hardware color index and <code>palette_data</code> index will be incremented until <code>count</code> number of colors have been set.
</p></li></ul>

<a name="grub_005fvideo_005fget_005fpalette"></a>
<h4 class="subsection">9.1.6 grub_video_get_palette</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_get_palette (unsigned int start, unsigned int count, struct grub_video_palette_data *palette_data);
</pre></div>
<div class="example">
<pre class="example">struct grub_video_palette_data
{
    grub_uint8_t r; /* Red color value (0-255). */
    grub_uint8_t g; /* Green color value (0-255). */
    grub_uint8_t b; /* Blue color value (0-255). */
    grub_uint8_t a; /* Reserved bits value (0-255). */
};
</pre></div>
</li><li> Description:

<p>Used to query indexed color palettes. If mode is RGB mode, colors will be copied from emulated palette data. In Indexed Color modes, palettes will be read from hardware. Color values will be converted to suit structure format. <code>start</code> will tell what hardware color index (or emulated color index) will be used as a source for first indice of <code>palette_data</code>, after that both hardware color index and <code>palette_data</code> index will be incremented until <code>count</code> number of colors have been read.
</p></li></ul>

<a name="grub_005fvideo_005fset_005farea_005fstatus"></a>
<h4 class="subsection">9.1.7 grub_video_set_area_status</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">grub_err_t
grub_video_set_area_status (grub_video_area_status_t area_status);
</pre></div>
<div class="example">
<pre class="example">enum grub_video_area_status_t
  {
    GRUB_VIDEO_AREA_DISABLED,
    GRUB_VIDEO_AREA_ENABLED
  };
</pre></div>

</li><li> Description:

<p>Used to set area drawing mode for redrawing the specified region. Draw commands
are performed in the intersection of the viewport and the region called area.
Coordinates remain related to the viewport. If draw commands try to draw over
the area, they are clipped.
Set status to DISABLED if you need to draw everything.
Set status to ENABLED and region to the desired rectangle to redraw everything
inside the region leaving everything else intact.
Should be used for redrawing of active elements.
</p></li></ul>

<a name="grub_005fvideo_005fget_005farea_005fstatus"></a>
<h4 class="subsection">9.1.8 grub_video_get_area_status</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">grub_err_r
grub_video_get_area_status (grub_video_area_status_t *area_status);
</pre></div>

</li><li> Description:
Used to query the area status.
</li></ul>

<a name="grub_005fvideo_005fset_005fviewport"></a>
<h4 class="subsection">9.1.9 grub_video_set_viewport</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_set_viewport (unsigned int x, unsigned int y, unsigned int width, unsigned int height);
</pre></div>
</li><li> Description:

<p>Used to specify viewport where draw commands are performed. When viewport is set, all draw commands coordinates relate to those specified by <code>x</code> and <code>y</code>. If draw commands try to draw over viewport, they are clipped. If developer requests larger than possible viewport, width and height will be clamped to fit screen. If <code>x</code> and <code>y</code> are out of bounds, all functions drawing to screen will not be displayed. In order to maximize viewport, use <code>grub_video_get_info</code> to query actual screen dimensions and provide that information to this function.
</p></li></ul>

<a name="grub_005fvideo_005fget_005fviewport"></a>
<h4 class="subsection">9.1.10 grub_video_get_viewport</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_get_viewport (unsigned int *x, unsigned int *y, unsigned int *width, unsigned int *height);
</pre></div>
</li><li> Description:

<p>Used to query current viewport dimensions. Software developer can use this to choose best way to render contents of the viewport.
</p></li></ul>

<a name="grub_005fvideo_005fset_005fregion"></a>
<h4 class="subsection">9.1.11 grub_video_set_region</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_set_region (unsigned int x, unsigned int y, unsigned int width, unsigned int height);
</pre></div>
</li><li> Description:

<p>Used to specify the region of the screen which should be redrawn. Use absolute
values. When the region is set and area status is ENABLE all draw commands will
be performed inside the interseption of region and viewport named area.
If draw commands try to draw over viewport, they are clipped. If developer
requests larger than possible region, width and height will be clamped to fit
screen. Should be used for redrawing of active elements.
</p></li></ul>

<a name="grub_005fvideo_005fget_005fregion"></a>
<h4 class="subsection">9.1.12 grub_video_get_region</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_get_region (unsigned int *x, unsigned int *y, unsigned int *width, unsigned int *height);
</pre></div>
</li><li> Description:

<p>Used to query current region dimensions.
</p></li></ul>

<a name="grub_005fvideo_005fmap_005fcolor"></a>
<h4 class="subsection">9.1.13 grub_video_map_color</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_video_color_t
grub_video_map_color (grub_uint32_t color_name);
</pre></div>
</li><li> Description:

<p>Map color can be used to support color themes in GRUB. There will be collection of color names that can be used to query actual screen mapped color data. Examples could be <code>GRUB_COLOR_CONSOLE_BACKGROUND</code>, <code>GRUB_COLOR_CONSOLE_TEXT</code>. The actual color defines are not specified at this point.
</p></li></ul>

<a name="grub_005fvideo_005fmap_005frgb"></a>
<h4 class="subsection">9.1.14 grub_video_map_rgb</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_video_color_t
grub_video_map_rgb (grub_uint8_t red, grub_uint8_t green, grub_uint8_t blue);
</pre></div>
</li><li> Description:

<p>Map RGB values to compatible screen color data. Values are expected to be in range 0-255 and in RGB modes they will be converted to screen color data. In index color modes, index color palette will be searched for specified color and then index is returned.
</p></li></ul>

<a name="grub_005fvideo_005fmap_005frgba"></a>
<h4 class="subsection">9.1.15 grub_video_map_rgba</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_video_color_t
grub_video_map_rgba (grub_uint8_t red, grub_uint8_t green, grub_uint8_t blue, grub_uint8_t alpha);
</pre></div>
</li><li> Description:

<p>Map RGBA values to compatible screen color data. Values are expected to be in range 0-255. In RGBA modes they will be converted to screen color data. In index color modes, index color palette will be searched for best matching color and its index is returned.
</p></li></ul>

<a name="grub_005fvideo_005funmap_005fcolor"></a>
<h4 class="subsection">9.1.16 grub_video_unmap_color</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_unmap_color (grub_video_color_t color, grub_uint8_t *red, grub_uint8_t *green, grub_uint8_t *blue, grub_uint8_t *alpha);
</pre></div>
</li><li> Description:

<p>Unmap color value from <code>color</code> to color channels in <code>red</code>, <code>green</code>, <code>blue</code> and <code>alpha</code>. Values will be in range 0-255. Active rendering target will be used for color domain. In case alpha information is not available in rendering target, it is assumed to be opaque (having value 255).
</p></li></ul>

<a name="grub_005fvideo_005ffill_005frect"></a>
<h4 class="subsection">9.1.17 grub_video_fill_rect</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_fill_rect (grub_video_color_t color, int x, int y, unsigned int width, unsigned int height);
</pre></div>
</li><li> Description:

<p>Fill specified area limited by given coordinates within specified viewport. Negative coordinates are accepted in order to allow easy moving of rectangle within viewport. If coordinates are negative, area of the rectangle will be shrinken to follow size limits of the viewport.
</p>
<p>Software developer should use either <code>grub_video_map_color</code>, <code>grub_video_map_rgb</code> or <code>grub_video_map_rgba</code> to map requested color to <code>color</code> parameter.
</p></li></ul>

<a name="grub_005fvideo_005fblit_005fglyph"></a>
<h4 class="subsection">9.1.18 grub_video_blit_glyph</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_blit_glyph (struct grub_font_glyph *glyph, grub_video_color_t color, int x, int y);
</pre></div>
<div class="example">
<pre class="example">struct grub_font_glyph {
    /* TBD. */
};
</pre></div>
</li><li> Description:

<p>Used to blit glyph to viewport in specified coodinates. If glyph is at edge of viewport, pixels outside of viewport will be clipped out. Software developer should use either <code>grub_video_map_rgb</code> or <code>grub_video_map_rgba</code> to map requested color to <code>color</code> parameter.
</p></li></ul>

<a name="grub_005fvideo_005fblit_005fbitmap"></a>
<h4 class="subsection">9.1.19 grub_video_blit_bitmap</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_blit_bitmap (struct grub_video_bitmap *bitmap, enum grub_video_blit_operators oper, int x, int y, int offset_x, int offset_y, unsigned int width, unsigned int height);
</pre></div>
<div class="example">
<pre class="example">struct grub_video_bitmap
{
    /* TBD. */
};

enum grub_video_blit_operators
  {
    GRUB_VIDEO_BLIT_REPLACE,
    GRUB_VIDEO_BLIT_BLEND
  };
</pre></div>
</li><li> Description:

<p>Used to blit bitmap to viewport in specified coordinates. If part of bitmap is outside of viewport region, it will be clipped out. Offsets affect bitmap position where data will be copied from. Negative values for both viewport coordinates and bitmap offset coordinates are allowed. If data is looked out of bounds of bitmap, color value will be assumed to be transparent. If viewport coordinates are negative, area of the blitted rectangle will be shrinken to follow size limits of the viewport and bitmap. Blitting operator <code>oper</code> specifies should source pixel replace data in screen or blend with pixel alpha value.
</p>
<p>Software developer should use <code>grub_video_bitmap_create</code> or <code>grub_video_bitmap_load</code> to create or load bitmap data.
</p></li></ul>

<a name="grub_005fvideo_005fblit_005frender_005ftarget"></a>
<h4 class="subsection">9.1.20 grub_video_blit_render_target</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_blit_render_target (struct grub_video_render_target *source, enum grub_video_blit_operators oper, int x, int y, int offset_x, int offset_y, unsigned int width, unsigned int height);
</pre></div>
<div class="example">
<pre class="example">struct grub_video_render_target {
    /* This is private data for video driver. Should not be accessed from elsewhere directly.  */
};

enum grub_video_blit_operators
  {
    GRUB_VIDEO_BLIT_REPLACE,
    GRUB_VIDEO_BLIT_BLEND
  };
</pre></div>
</li><li> Description:

<p>Used to blit source render target to viewport in specified coordinates. If part of source render target is outside of viewport region, it will be clipped out. If blitting operator is specified and source contains alpha values, resulting pixel color components will be calculated using formula ((src_color * src_alpha) + (dst_color * (255 - src_alpha)) / 255, if target buffer has alpha, it will be set to src_alpha. Offsets affect render target position where data will be copied from. If data is looked out of bounds of render target, color value will be assumed to be transparent. Blitting operator <code>oper</code> specifies should source pixel replace data in screen or blend with pixel alpha value.
</p></li></ul>

<a name="grub_005fvideo_005fscroll"></a>
<h4 class="subsection">9.1.21 grub_video_scroll</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_scroll (grub_video_color_t color, int dx, int dy);
</pre></div>
</li><li> Description:

<p>Used to scroll viewport to specified direction. New areas are filled with specified color. This function is used when screen is scroller up in video terminal.
</p></li></ul>

<a name="grub_005fvideo_005fswap_005fbuffers"></a>
<h4 class="subsection">9.1.22 grub_video_swap_buffers</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_swap_buffers (void);
</pre></div>
</li><li> Description:

<p>If double buffering is enabled, this swaps frontbuffer and backbuffer, in order to show values drawn to back buffer. Video driver is free to choose how this operation is techincally done.
</p></li></ul>

<a name="grub_005fvideo_005fcreate_005frender_005ftarget"></a>
<h4 class="subsection">9.1.23 grub_video_create_render_target</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_create_render_target (struct grub_video_render_target **result, unsigned int width, unsigned int height, unsigned int mode_type);
</pre></div>
<div class="example">
<pre class="example">struct grub_video_render_target {
    /* This is private data for video driver. Should not be accessed from elsewhere directly.  */
};
</pre></div>
</li><li> Description:

<p>Driver will use information provided to it to create best fitting render target. <code>mode_type</code> will be used to guide on selecting what features are wanted for render target. Supported values for <code>mode_type</code> are <code>GRUB_VIDEO_MODE_TYPE_INDEX_COLOR</code> for index color modes, <code>GRUB_VIDEO_MODE_TYPE_RGB</code> for direct RGB color modes and <code>GRUB_VIDEO_MODE_TYPE_ALPHA</code> for alpha component.
</p></li></ul>

<a name="grub_005fvideo_005fdelete_005frender_005ftarget"></a>
<h4 class="subsection">9.1.24 grub_video_delete_render_target</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_delete_render_target (struct grub_video_render_target *target);
</pre></div>
</li><li> Description:

<p>Used to delete previously created render target. If <code>target</code> contains <code>NULL</code> pointer, nothing will be done. If render target is correctly destroyed, GRUB_ERR_NONE is returned.
</p></li></ul>

<a name="grub_005fvideo_005fset_005factive_005frender_005ftarget"></a>
<h4 class="subsection">9.1.25 grub_video_set_active_render_target</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_set_active_render_target (struct grub_video_render_target *target);
</pre></div>
</li><li> Description:

<p>Sets active render target. If this comand is successful all drawing commands will be done to specified <code>target</code>. There is also special values for target, <code>GRUB_VIDEO_RENDER_TARGET_DISPLAY</code> used to reference screen&rsquo;s front buffer, <code>GRUB_VIDEO_RENDER_TARGET_FRONT_BUFFER</code> used to reference screen&rsquo;s front buffer (alias for <code>GRUB_VIDEO_RENDER_TARGET_DISPLAY</code>) and <code>GRUB_VIDEO_RENDER_TARGET_BACK_BUFFER</code> used to reference back buffer (if double buffering is enabled). If render target is correclty switched GRUB_ERR_NONE is returned. In no any event shall there be non drawable active render target.
</p>
</li></ul>
<a name="grub_005fvideo_005fget_005factive_005frender_005ftarget"></a>
<h4 class="subsection">9.1.26 grub_video_get_active_render_target</h4>
<ul>
<li> Prototype:

<div class="example">
<pre class="example">grub_err_t
grub_video_get_active_render_target (struct grub_video_render_target **target);
</pre></div>
</li><li> Description:

<p>Returns currently active render target. It returns value in <code>target</code> that can be subsequently issued back to <code>grub_video_set_active_render_target</code>.
</p></li></ul>

<hr>
<a name="Example-usage-of-Video-API"></a>
<div class="header">
<p>
Next: <a href="#Bitmap-API" accesskey="n" rel="next">Bitmap API</a>, Previous: <a href="#Video-API" accesskey="p" rel="prev">Video API</a>, Up: <a href="#Video-Subsystem" accesskey="u" rel="up">Video Subsystem</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Example-usage-of-Video-API-1"></a>
<h3 class="section">9.2 Example usage of Video API</h3>
<a name="Example-of-screen-setup"></a>
<h4 class="subsection">9.2.1 Example of screen setup</h4>
<div class="example">
<pre class="example">grub_err_t rc;
/* Try to initialize video mode 1024 x 768 with direct RGB.  */
rc = grub_video_setup (1024, 768, GRUB_VIDEO_MODE_TYPE_RGB);
if (rc != GRUB_ERR_NONE)
{
  /* Fall back to standard VGA Index Color mode.  */
  rc = grub_video_setup (640, 480, GRUB_VIDEO_MODE_TYPE_INDEX);
  if (rc != GRUB_ERR_NONE)
  {
  /* Handle error.  */
  }
}
</pre></div>
<a name="Example-of-setting-up-console-viewport"></a>
<h4 class="subsection">9.2.2 Example of setting up console viewport</h4>
<div class="example">
<pre class="example">grub_uint32_t x, y, width, height;
grub_video_color_t color;
struct grub_font_glyph glyph;
grub_err_t rc;
/* Query existing viewport.  */
grub_video_get_viewport (&amp;x, &amp;y, &amp;width, &amp;height);
/* Fill background.  */
color = grub_video_map_color (GRUB_COLOR_BACKGROUND);
grub_video_fill_rect (color, 0, 0, width, height);
/* Setup console viewport.  */
grub_video_set_viewport (x + 10, y + 10, width - 20, height - 20);
grub_video_get_viewport (&amp;x, &amp;y, &amp;width, &amp;height);
color = grub_video_map_color (GRUB_COLOR_CONSOLE_BACKGROUND);
grub_video_fill_rect (color, 0, 0, width, height);
/* Draw text to viewport.  */
color = grub_video_map_color (GRUB_COLOR_CONSOLE_TEXT);
grub_font_get_glyph ('X', &amp;glyph);
grub_video_blit_glyph (&amp;glyph, color, 0, 0);
</pre></div>

<hr>
<a name="Bitmap-API"></a>
<div class="header">
<p>
Previous: <a href="#Example-usage-of-Video-API" accesskey="p" rel="prev">Example usage of Video API</a>, Up: <a href="#Video-Subsystem" accesskey="u" rel="up">Video Subsystem</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Bitmap-API-1"></a>
<h3 class="section">9.3 Bitmap API</h3>
<a name="grub_005fvideo_005fbitmap_005fcreate"></a>
<h4 class="subsection">9.3.1 grub_video_bitmap_create</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">grub_err_t grub_video_bitmap_create (struct grub_video_bitmap **bitmap, unsigned int width, unsigned int height, enum grub_video_blit_format blit_format)
</pre></div>

</li><li> Description:

<p>Creates a new bitmap with given dimensions and blitting format. Allocated bitmap data can then be modified freely and finally blitted with <code>grub_video_blit_bitmap</code> to rendering target.
</p></li></ul>

<a name="grub_005fvideo_005fbitmap_005fdestroy"></a>
<h4 class="subsection">9.3.2 grub_video_bitmap_destroy</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">grub_err_t grub_video_bitmap_destroy (struct grub_video_bitmap *bitmap);
</pre></div>

</li><li> Description:

<p>When bitmap is no longer needed, it can be freed from memory using this command. <code>bitmap</code> is previously allocated bitmap with <code>grub_video_bitmap_create</code> or loaded with <code>grub_video_bitmap_load</code>.
</p></li></ul>

<a name="grub_005fvideo_005fbitmap_005fload"></a>
<h4 class="subsection">9.3.3 grub_video_bitmap_load</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">grub_err_t grub_video_bitmap_load (struct grub_video_bitmap **bitmap, const char *filename);
</pre></div>

</li><li> Description:

<p>Tries to load given bitmap (<code>filename</code>) using registered bitmap loaders. In case bitmap format is not recognized or supported error <code>GRUB_ERR_BAD_FILE_TYPE</code> is returned.
</p></li></ul>

<a name="grub_005fvideo_005fbitmap_005fget_005fwidth"></a>
<h4 class="subsection">9.3.4 grub_video_bitmap_get_width</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">unsigned int grub_video_bitmap_get_width (struct grub_video_bitmap *bitmap);
</pre></div>

</li><li> Description:

<p>Returns bitmap width.
</p></li></ul>

<a name="grub_005fvideo_005fbitmap_005fget_005fheight"></a>
<h4 class="subsection">9.3.5 grub_video_bitmap_get_height</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">unsigned int grub_video_bitmap_get_height (struct grub_video_bitmap *bitmap);
</pre></div>

</li><li> Description:

<p>Return bitmap height.
</p></li></ul>

<a name="grub_005fvideo_005fbitmap_005fget_005fmode_005finfo"></a>
<h4 class="subsection">9.3.6 grub_video_bitmap_get_mode_info</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">void grub_video_bitmap_get_mode_info (struct grub_video_bitmap *bitmap, struct grub_video_mode_info *mode_info);
</pre></div>

</li><li> Description:

<p>Returns bitmap format details in form of <code>grub_video_mode_info</code>.
</p></li></ul>

<a name="grub_005fvideo_005fbitmap_005fget_005fdata"></a>
<h4 class="subsection">9.3.7 grub_video_bitmap_get_data</h4>
<ul>
<li> Prototype:
<div class="example">
<pre class="example">void *grub_video_bitmap_get_data (struct grub_video_bitmap *bitmap);
</pre></div>

</li><li> Description:

<p>Return pointer to bitmap data. Contents of the pointed data can be freely modified. There is no extra protection against going off the bounds so you have to be carefull how to access the data.
</p></li></ul>

<hr>
<a name="PFF2-Font-File-Format"></a>
<div class="header">
<p>
Next: <a href="#Graphical-Menu-Software-Design" accesskey="n" rel="next">Graphical Menu Software Design</a>, Previous: <a href="#Video-Subsystem" accesskey="p" rel="prev">Video Subsystem</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="PFF2-Font-File-Format-1"></a>
<h2 class="chapter">10 PFF2 Font File Format</h2>

<hr>
<a name="Introduction"></a>
<div class="header">
<p>
Next: <a href="#File-Structure" accesskey="n" rel="next">File Structure</a>, Up: <a href="#PFF2-Font-File-Format" accesskey="u" rel="up">PFF2 Font File Format</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Introduction-1"></a>
<h3 class="section">10.1 Introduction</h3>

<p>The goal of this format is to provide a bitmap font format that is simple to
use, compact, and cleanly supports Unicode.
</p>

<a name="Goals-of-the-GRUB-Font-Format"></a>
<h4 class="subsection">10.1.1 Goals of the GRUB Font Format</h4>

<ul>
<li> Simple to read and use.
Since GRUB will only be reading the font files,
we are more concerned with making the code to read the font simple than we
are with writing the font.

</li><li> Compact storage.
The fonts will generally be stored in a small boot
partition where GRUB is located, and this may be on a removable storage
device such as a CD or USB flash drive where space is more limited than it
is on most hard drives.

</li><li> Unicode.
GRUB should not have to deal with multiple character
encodings.  The font should always use Unicode character codes for simple
internationalization.
</li></ul>

<a name="Why-Another-Font-Format_003f"></a>
<h4 class="subsection">10.1.2 Why Another Font Format?</h4>

<p>There are many existing bitmap font formats that GRUB could use.  However,
there are aspects of these formats that may make them less than suitable for
use in GRUB at this time:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>BDF</samp>&rsquo;</dt>
<dd><p>Inefficient storage; uses ASCII to describe properties and 
hexadecimal numbers in ASCII for the bitmap rows.
</p></dd>
<dt>&lsquo;<samp>PCF</samp>&rsquo;</dt>
<dd><p>Many format variations such as byte order and bitmap padding (rows
padded to byte, word, etc.) would result in more complex code to
handle the font format.
</p></dd>
</dl>

<hr>
<a name="File-Structure"></a>
<div class="header">
<p>
Next: <a href="#Font-Metrics" accesskey="n" rel="next">Font Metrics</a>, Previous: <a href="#Introduction" accesskey="p" rel="prev">Introduction</a>, Up: <a href="#PFF2-Font-File-Format" accesskey="u" rel="up">PFF2 Font File Format</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="File-Structure-1"></a>
<h3 class="section">10.2 File Structure</h3>

<p>A file <strong>section</strong> consists of a 4-byte name, a 32-bit big-endian length (not
including the name or length), and then <var>length</var> more section-type-specific 
bytes.
</p>
<p>The standard file extension for PFF2 font files is <samp>.pf2</samp>.
</p>

<a name="Section-Types"></a>
<h4 class="subsection">10.2.1 Section Types</h4>

<dl compact="compact">
<dt>&lsquo;<samp>FILE</samp>&rsquo;</dt>
<dd><p><strong>File type ID</strong> (ASCII string).  This must be the first section in the file.  It has length 4
and the contents are the four bytes of the ASCII string &lsquo;<samp>PFF2</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>NAME</samp>&rsquo;</dt>
<dd><p><strong>Font name</strong> (ASCII string).  This is the full font name including family,
weight, style, and point size.  For instance, &quot;Helvetica Bold Italic 14&quot;.
</p>
</dd>
<dt>&lsquo;<samp>FAMI</samp>&rsquo;</dt>
<dd><p><strong>Font family name</strong> (ASCII string).  For instance, &quot;Helvetica&quot;.  This should
be included so that intelligent font substitution can take place.
</p>
</dd>
<dt>&lsquo;<samp>WEIG</samp>&rsquo;</dt>
<dd><p><strong>Font weight</strong> (ASCII string).  Valid values are &lsquo;<samp>bold</samp>&rsquo; and &lsquo;<samp>normal</samp>&rsquo;.
This should be included so that intelligent font substitution can take
place.
</p>
</dd>
<dt>&lsquo;<samp>SLAN</samp>&rsquo;</dt>
<dd><p><strong>Font slant</strong> (ASCII string).  Valid values are &lsquo;<samp>italic</samp>&rsquo; and &lsquo;<samp>normal</samp>&rsquo;.
This should be included so that intelligent font substitution can take
place.
</p>
</dd>
<dt>&lsquo;<samp>PTSZ</samp>&rsquo;</dt>
<dd><p><strong>Font point size</strong> (uint16be).
</p>
</dd>
<dt>&lsquo;<samp>MAXW</samp>&rsquo;</dt>
<dd><p><strong>Maximum character width in pixels</strong> (uint16be).
</p>
</dd>
<dt>&lsquo;<samp>MAXH</samp>&rsquo;</dt>
<dd><p><strong>Maximum character height in pixels</strong> (uint16be).
</p>
</dd>
<dt>&lsquo;<samp>ASCE</samp>&rsquo;</dt>
<dd><p><strong>Ascent in pixels</strong> (uint16be).  See <a href="#Font-Metrics">Font Metrics</a>, for details.
</p>
</dd>
<dt>&lsquo;<samp>DESC</samp>&rsquo;</dt>
<dd><p><strong>Descent in pixels</strong> (uint16be).  See <a href="#Font-Metrics">Font Metrics</a>, for details.
</p>
</dd>
<dt>&lsquo;<samp>CHIX</samp>&rsquo;</dt>
<dd><p><strong>Character index.</strong>
The character index begins with a 32-bit big-endian unsigned integer
indicating the total size of the section, not including this size value.
For each character, there is an instance of the following entry structure:
</p>
<ul>
<li> <strong>Unicode code point.</strong> (32-bit big-endian integer.)

</li><li> <strong>Storage flags.</strong> (byte.)
       
<ul>
<li> Bits 2..0:

<p>If equal to 000 binary, then the character data is stored
uncompressed beginning at the offset indicated by the character&rsquo;s
<strong>offset</strong> value.
</p>
<p>If equal to 001 binary, then the character data is stored within a 
compressed character definition block that begins at the offset 
within the file indicated by the character&rsquo;s <strong>offset</strong> value.
</p></li></ul>

</li><li> <strong>Offset.</strong> (32-bit big-endian integer.)

<p>A marker that indicates the remainder of the file is data accessed via
the character index (CHIX) section.  When reading this font file, the rest
of the file can be ignored when scanning the sections.  The length should
be set to -1 (0xFFFFFFFF).
</p>
<p>Supported data structures:
</p>
<p>Character definition
Each character definition consists of:
</p>
<ul>
<li> <strong>Width.</strong>
Width of the bitmap in pixels.  The bitmap&rsquo;s extents 
represent the glyph&rsquo;s bounding box.  <code>uint16be</code>.

</li><li> <strong>Height.</strong>
Height of the bitmap in pixels.  The bitmap&rsquo;s extents
represent the glyph&rsquo;s bounding box.  <code>uint16be</code>.

</li><li> <strong>X offset.</strong>
The number of pixels to shift the bitmap by
horizontally before drawing the character. <code>int16be</code>.

</li><li> <strong>Y offset.</strong>
The number of pixels to shift the bitmap by
vertically before drawing the character. <code>int16be</code>.

</li><li> <strong>Device width.</strong>
The number of pixels to advance horizontally from
this character&rsquo;s origin to the origin of the next character.
<code>int16be</code>.

</li><li> <strong>Bitmap data.</strong>
This is encoded as a string of bits.  It is
organized as a row-major, top-down, left-to-right bitmap.  The most
significant bit of each byte is taken to be the leftmost or uppermost
bit in the byte.  For the sake of compact storage, rows are not padded
to byte boundaries (i.e., a single byte may contain bits belonging to
multiple rows).  The last byte of the bitmap <strong>is</strong> padded with zero
bits in the bits positions to the right of the last used bit if the
bitmap data does not fill the last byte.  
         
<p>The length of the <strong>bitmap data</strong> field is (<var>width</var> * <var>height</var> + 7) / 8
using integer arithmetic, which is equivalent to ceil(<var>width</var> *
<var>height</var> / 8) using real number arithmetic.
</p>
<p>It remains to be determined whether bitmap fonts usually make all
glyph bitmaps the same height, or if smaller glyphs are stored with
bitmaps having a lesser height.  In the latter case, the baseline
would have to be used to calculate the location the bitmap should be
anchored at on screen.
</p></li></ul>

</li></ul>
</dd>
</dl>

<hr>
<a name="Font-Metrics"></a>
<div class="header">
<p>
Previous: <a href="#File-Structure" accesskey="p" rel="prev">File Structure</a>, Up: <a href="#PFF2-Font-File-Format" accesskey="u" rel="up">PFF2 Font File Format</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Font-Metrics-1"></a>
<h3 class="section">10.3 Font Metrics</h3>

<ul>
<li> Ascent.
The distance from the baseline to the top of most characters.
Note that in some cases characters may extend above the ascent.

</li><li> Descent.
The distance from the baseline to the bottom of most characters.  Note that
in some cases characters may extend below the descent.
 
</li><li> Leading.
The amount of space, in pixels, to leave between the descent of one line of
text and the ascent of the next line.  This metrics is not specified in the
current file format; instead, the font rendering engine calculates a
reasonable leading value based on the other font metrics.

</li><li> Horizonal leading.
The amount of space, in pixels, to leave horizontally between the left and
right edges of two adjacent glyphs.  The <strong>device width</strong> field determines
the effective leading value that is used to render the font.

</li></ul>
<img src="font_char_metrics.png" alt="font_char_metrics">
   
<p>An illustration of how the various font metrics apply to characters.
</p>

<hr>
<a name="Graphical-Menu-Software-Design"></a>
<div class="header">
<p>
Next: <a href="#Lockdown-framework" accesskey="n" rel="next">Lockdown framework</a>, Previous: <a href="#PFF2-Font-File-Format" accesskey="p" rel="prev">PFF2 Font File Format</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Graphical-Menu-Software-Design-1"></a>
<h2 class="chapter">11 Graphical Menu Software Design</h2>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Introduction_005f2" accesskey="1">Introduction_2</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Startup-Sequence" accesskey="2">Startup Sequence</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#GUI-Components" accesskey="3">GUI Components</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Command-Line-Window" accesskey="4">Command Line Window</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Introduction_005f2"></a>
<div class="header">
<p>
Next: <a href="#Startup-Sequence" accesskey="n" rel="next">Startup Sequence</a>, Up: <a href="#Graphical-Menu-Software-Design" accesskey="u" rel="up">Graphical Menu Software Design</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Introduction-2"></a>
<h3 class="section">11.1 Introduction</h3>

<p>The &lsquo;<samp>gfxmenu</samp>&rsquo; module provides a graphical menu interface for GRUB 2.  It
functions as an alternative to the menu interface provided by the &lsquo;<samp>normal</samp>&rsquo;
module, which uses the grub terminal interface to display a menu on a
character-oriented terminal.
</p>
<p>The graphical menu uses the GRUB video API, which is currently for the VESA
BIOS extensions (VBE) 2.0+.  This is supported on the i386-pc platform.
However, the graphical menu itself does not depend on using VBE, so if another
GRUB video driver were implemented, the &lsquo;<samp>gfxmenu</samp>&rsquo; graphical menu would work
on the new video driver as well.
</p>

<hr>
<a name="Startup-Sequence"></a>
<div class="header">
<p>
Next: <a href="#GUI-Components" accesskey="n" rel="next">GUI Components</a>, Previous: <a href="#Introduction_005f2" accesskey="p" rel="prev">Introduction_2</a>, Up: <a href="#Graphical-Menu-Software-Design" accesskey="u" rel="up">Graphical Menu Software Design</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Startup-Sequence-1"></a>
<h3 class="section">11.2 Startup Sequence</h3>

<ul>
<li> grub_enter_normal_mode [normal/main.c]
</li><li> grub_normal_execute [normal/main.c]
</li><li> read_config_file [normal/main.c]
</li><li> (When <samp>gfxmenu.mod</samp> is loaded with <code>insmod</code>, it will call <code>grub_menu_viewer_register()</code> to register itself.)
</li><li> GRUB_MOD_INIT (gfxmenu) [gfxmenu/gfxmenu.c]
</li><li> grub_menu_viewer_register [kern/menu_viewer.c]
</li><li> grub_menu_viewer_show_menu [kern/menu_viewer.c]
</li><li> get_current_menu_viewer() [kern/menu_viewer.c]
</li><li> show_menu() [gfxmenu/gfxmenu.c]
</li><li> grub_gfxmenu_model_new [gfxmenu/model.c]
</li><li> grub_gfxmenu_view_new [gfxmenu/view.c]
</li><li> set_graphics_mode [gfxmenu/view.c]
</li><li> grub_gfxmenu_view_load_theme [gfxmenu/theme_loader.c]
</li></ul>

<hr>
<a name="GUI-Components"></a>
<div class="header">
<p>
Next: <a href="#Command-Line-Window" accesskey="n" rel="next">Command Line Window</a>, Previous: <a href="#Startup-Sequence" accesskey="p" rel="prev">Startup Sequence</a>, Up: <a href="#Graphical-Menu-Software-Design" accesskey="u" rel="up">Graphical Menu Software Design</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GUI-Components-1"></a>
<h3 class="section">11.3 GUI Components</h3>

<p>The graphical menu implements a GUI component system that supports a
container-based layout system.  Components can be added to containers, and
containers (which are a type of component) can then be added to other
containers, to form a tree of components.  Currently, the root component of
this tree is a &lsquo;<samp>canvas</samp>&rsquo; component, which allows manual layout of its child
components.
</p>
<p>Components (non-container):
</p>
<ul>
<li> label
</li><li> image
</li><li> progress_bar
</li><li> circular_progress
</li><li> list (currently hard coded to be a boot menu list)
</li></ul>

<p>Containers:
</p>
<ul>
<li> canvas
</li><li> hbox
</li><li> vbox
</li></ul>

<p>The GUI component instances are created by the theme loader in
<samp>gfxmenu/theme_loader.c</samp> when a theme is loaded.  Theme files specify
statements such as &lsquo;<samp>+vbox{ +label { text=&quot;Hello&quot; } +label{ text=&quot;World&quot; } }</samp>&rsquo;
to add components to the component tree root.  By nesting the component
creation statements in the theme file, the instantiated components are nested
the same way.
</p>
<p>When a component is added to a container, that new child is considered <strong>owned</strong>
by the container.  Great care should be taken if the caller retains a
reference to the child component, since it will be destroyed if its parent
container is destroyed.  A better choice instead of storing a pointer to the
child component is to use the component ID to find the desired component.
Component IDs do not have to be unique (it is often useful to have multiple
components with an ID of &quot;__timeout__&quot;, for instance).
</p>
<p>In order to access and use components in the component tree, there are two
functions (defined in <samp>gfxmenu/gui_util.c</samp>) that are particularly useful:
</p>
<ul>
<li> <code>grub_gui_find_by_id (root, id, callback, userdata)</code>:

<p>This function ecursively traverses the component tree rooted at <var>root</var>, and
for every component that has an ID equal to <var>id</var>, calls the function pointed
to by <var>callback</var> with the matching component and the void pointer <var>userdata</var>
as arguments.  The callback function can do whatever is desired to use the
component passed in.
</p>
</li><li> <code>grub_gui_iterate_recursively (root, callback, userdata)</code>:

<p>This function calls the function pointed to by <var>callback</var> for every
component that is a descendant of <var>root</var> in the component tree.  When the
callback function is called, the component and the void pointer <var>userdata</var>
as arguments.  The callback function can do whatever is desired to use the
component passed in.
</p></li></ul>

<hr>
<a name="Command-Line-Window"></a>
<div class="header">
<p>
Previous: <a href="#GUI-Components" accesskey="p" rel="prev">GUI Components</a>, Up: <a href="#Graphical-Menu-Software-Design" accesskey="u" rel="up">Graphical Menu Software Design</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Command-Line-Window-1"></a>
<h3 class="section">11.4 Command Line Window</h3>

<p>The terminal window used to provide command line access within the graphical
menu is managed by <samp>gfxmenu/view.c</samp>.  The &lsquo;<samp>gfxterm</samp>&rsquo; terminal is used, and
it has been modified to allow rendering to an offscreen render target to allow
it to be composed into the double buffering system that the graphical menu
view uses.  This is bad for performance, however, so it would probably be a
good idea to make it possible to temporarily disable double buffering as long
as the terminal window is visible.  There are still unresolved problems that
occur when commands are executed from the terminal window that change the
graphics mode.  It&rsquo;s possible that making <code>grub_video_restore()</code> return to
the graphics mode that was in use before <code>grub_video_setup()</code> was called
might fix some of the problems.
</p>

<hr>
<a name="Lockdown-framework"></a>
<div class="header">
<p>
Next: <a href="#Copying-This-Manual" accesskey="n" rel="next">Copying This Manual</a>, Previous: <a href="#Graphical-Menu-Software-Design" accesskey="p" rel="prev">Graphical Menu Software Design</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Lockdown-framework-1"></a>
<h2 class="chapter">12 Lockdown framework</h2>

<p>The GRUB can be locked down, which is a restricted mode where some operations
are not allowed. For instance, some commands cannot be used when the GRUB is
locked down.
</p>
<p>The function
<code>grub_lockdown()</code> is used to lockdown GRUB and the function
<code>grub_is_lockdown()</code> function can be used to check whether lockdown is
enabled or not. When enabled, the function returns &lsquo;<samp>GRUB_LOCKDOWN_ENABLED</samp>&rsquo;
and &lsquo;<samp>GRUB_LOCKDOWN_DISABLED</samp>&rsquo; when is not enabled.
</p>
<p>The following functions can be used to register the commands that can only be
used when lockdown is disabled:
</p>
<ul>
<li> <code>grub_cmd_lockdown()</code> registers command which should not run when the
GRUB is in lockdown mode.

</li><li> <code>grub_cmd_lockdown()</code> registers extended command which should not run
when the GRUB is in lockdown mode.

</li></ul>

<hr>
<a name="Copying-This-Manual"></a>
<div class="header">
<p>
Next: <a href="#Index" accesskey="n" rel="next">Index</a>, Previous: <a href="#Lockdown-framework" accesskey="p" rel="prev">Lockdown framework</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Copying-This-Manual-1"></a>
<h2 class="appendix">Appendix A Copying This Manual</h2>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#GNU-Free-Documentation-License" accesskey="1">GNU Free Documentation License</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">License for copying this manual.
</td></tr>
</table>

<hr>
<a name="GNU-Free-Documentation-License"></a>
<div class="header">
<p>
Up: <a href="#Copying-This-Manual" accesskey="u" rel="up">Copying This Manual</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GNU-Free-Documentation-License-1"></a>
<h3 class="appendixsec">A.1 GNU Free Documentation License</h3>

<a name="index-FDL_002c-GNU-Free-Documentation-License"></a>
<div align="center">Version 1.2, November 2002
</div>
<div class="display">
<pre class="display">Copyright &copy; 2000,2001,2002 Free Software Foundation, Inc.
51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
</pre></div>

<ol start="0">
<li> PREAMBLE

<p>The purpose of this License is to make a manual, textbook, or other
functional and useful document <em>free</em> in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.
</p>
<p>This License is a kind of &ldquo;copyleft&rdquo;, which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
license designed for free software.
</p>
<p>We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book.  We recommend this License
principally for works whose purpose is instruction or reference.
</p>
</li><li> APPLICABILITY AND DEFINITIONS

<p>This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License.  Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein.  The &ldquo;Document&rdquo;, below,
refers to any such manual or work.  Any member of the public is a
licensee, and is addressed as &ldquo;you&rdquo;.  You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.
</p>
<p>A &ldquo;Modified Version&rdquo; of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
</p>
<p>A &ldquo;Secondary Section&rdquo; is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
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them.
</p>
<p>The &ldquo;Invariant Sections&rdquo; are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.  If a
section does not fit the above definition of Secondary then it is not
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</p>
<p>The &ldquo;Cover Texts&rdquo; are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
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</p>
<p>A &ldquo;Transparent&rdquo; copy of the Document means a machine-readable copy,
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</p>
<p>The &ldquo;Title Page&rdquo; means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page.  For works in
formats which do not have any title page as such, &ldquo;Title Page&rdquo; means
the text near the most prominent appearance of the work&rsquo;s title,
preceding the beginning of the body of the text.
</p>
<p>A section &ldquo;Entitled XYZ&rdquo; means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language.  (Here XYZ stands for a
specific section name mentioned below, such as &ldquo;Acknowledgements&rdquo;,
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of such a section when you modify the Document means that it remains a
section &ldquo;Entitled XYZ&rdquo; according to this definition.
</p>
<p>The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document.  These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
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no effect on the meaning of this License.
</p>
</li><li> VERBATIM COPYING

<p>You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further
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compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.
</p>
<p>You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
</p>
</li><li> COPYING IN QUANTITY

<p>If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document&rsquo;s license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify
you as the publisher of these copies.  The front cover must present
the full title with all words of the title equally prominent and
visible.  You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.
</p>
<p>If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
</p>
<p>If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.
</p>
<p>It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.
</p>
</li><li> MODIFICATIONS

<p>You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it.  In addition, you must do these things in the Modified Version:
</p>
<ol type="A" start="1">
<li> Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document).  You may use the same title as a previous version
if the original publisher of that version gives permission.

</li><li> List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has fewer than five),
unless they release you from this requirement.

</li><li> State on the Title page the name of the publisher of the
Modified Version, as the publisher.

</li><li> Preserve all the copyright notices of the Document.

</li><li> Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.

</li><li> Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.

</li><li> Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document&rsquo;s license notice.

</li><li> Include an unaltered copy of this License.

</li><li> Preserve the section Entitled &ldquo;History&rdquo;, Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page.  If
there is no section Entitled &ldquo;History&rdquo; in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.

</li><li> Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on.  These may be placed in the &ldquo;History&rdquo; section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.

</li><li> For any section Entitled &ldquo;Acknowledgements&rdquo; or &ldquo;Dedications&rdquo;, Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.

</li><li> Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles.  Section numbers
or the equivalent are not considered part of the section titles.

</li><li> Delete any section Entitled &ldquo;Endorsements&rdquo;.  Such a section
may not be included in the Modified Version.

</li><li> Do not retitle any existing section to be Entitled &ldquo;Endorsements&rdquo; or
to conflict in title with any Invariant Section.

</li><li> Preserve any Warranty Disclaimers.
</li></ol>

<p>If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version&rsquo;s license notice.
These titles must be distinct from any other section titles.
</p>
<p>You may add a section Entitled &ldquo;Endorsements&rdquo;, provided it contains
nothing but endorsements of your Modified Version by various
parties&mdash;for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
</p>
<p>You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity.  If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
</p>
<p>The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
</p>
</li><li> COMBINING DOCUMENTS

<p>You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.
</p>
<p>The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
</p>
<p>In the combination, you must combine any sections Entitled &ldquo;History&rdquo;
in the various original documents, forming one section Entitled
&ldquo;History&rdquo;; likewise combine any sections Entitled &ldquo;Acknowledgements&rdquo;,
and any sections Entitled &ldquo;Dedications&rdquo;.  You must delete all
sections Entitled &ldquo;Endorsements.&rdquo;
</p>
</li><li> COLLECTIONS OF DOCUMENTS

<p>You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
</p>
<p>You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
</p>
</li><li> AGGREGATION WITH INDEPENDENT WORKS

<p>A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an &ldquo;aggregate&rdquo; if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation&rsquo;s users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.
</p>
<p>If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document&rsquo;s Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
</p>
</li><li> TRANSLATION

<p>Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections.  You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.
</p>
<p>If a section in the Document is Entitled &ldquo;Acknowledgements&rdquo;,
&ldquo;Dedications&rdquo;, or &ldquo;History&rdquo;, the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.
</p>
</li><li> TERMINATION

<p>You may not copy, modify, sublicense, or distribute the Document except
as expressly provided for under this License.  Any other attempt to
copy, modify, sublicense or distribute the Document is void, and will
automatically terminate your rights under this License.  However,
parties who have received copies, or rights, from you under this
License will not have their licenses terminated so long as such
parties remain in full compliance.
</p>
</li><li> FUTURE REVISIONS OF THIS LICENSE

<p>The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time.  Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.  See
<a href="http://www.gnu.org/copyleft/">http://www.gnu.org/copyleft/</a>.
</p>
<p>Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License &ldquo;or any later version&rdquo; applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.
</p></li></ol>

<a name="ADDENDUM_003a-How-to-use-this-License-for-your-documents"></a>
<h4 class="appendixsubsec">A.1.1 ADDENDUM: How to use this License for your documents</h4>

<p>To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
</p>
<div class="smallexample">
<pre class="smallexample">  Copyright (C)  <var>year</var>  <var>your name</var>.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.2
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.
</pre></div>

<p>If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the &ldquo;with...Texts.&rdquo; line with this:
</p>
<div class="smallexample">
<pre class="smallexample">    with the Invariant Sections being <var>list their titles</var>, with
    the Front-Cover Texts being <var>list</var>, and with the Back-Cover Texts
    being <var>list</var>.
</pre></div>

<p>If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
</p>
<p>If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
</p>

<hr>
<a name="Index"></a>
<div class="header">
<p>
Previous: <a href="#Copying-This-Manual" accesskey="p" rel="prev">Copying This Manual</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Index-1"></a>
<h2 class="unnumbered">Index</h2>

<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Index_cp_letter-F"><b>F</b></a>
 &nbsp; 
</td></tr></table>
<table class="index-cp" border="0">
<tr><td></td><th align="left">Index Entry</th><td>&nbsp;</td><th align="left"> Section</th></tr>
<tr><td colspan="4"> <hr></td></tr>
<tr><th><a name="Index_cp_letter-F">F</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-FDL_002c-GNU-Free-Documentation-License">FDL, GNU Free Documentation License</a>:</td><td>&nbsp;</td><td valign="top"><a href="#GNU-Free-Documentation-License">GNU Free Documentation License</a></td></tr>
<tr><td colspan="4"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: &nbsp; </th><td><a class="summary-letter" href="#Index_cp_letter-F"><b>F</b></a>
 &nbsp; 
</td></tr></table>

<hr>

</body>
</html>
PK��\�P�,D,D	grub.htmlnu�[���<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- This manual is for GNU GRUB (version 2.03,
17 March 2026).

</head>

<body lang="en">
<h1 class="settitle" align="center">GNU GRUB Manual 2.03</h1>

<a name="SEC_Contents"></a>
<h2 class="contents-heading">Table of Contents</h2>

<ul class="no-bullet">
  <li><a name="toc-Introduction-to-GRUB" href="#Introduction">1 Introduction to GRUB</a>
  <ul class="no-bullet">
    <li><a name="toc-Overview-1" href="#Overview">1.1 Overview</a></li>
    <li><a name="toc-History-of-GRUB" href="#History">1.2 History of GRUB</a></li>
    <li><a name="toc-Differences-from-previous-versions" href="#Changes-from-GRUB-Legacy">1.3 Differences from previous versions</a></li>
    <li><a name="toc-GRUB-features" href="#Features">1.4 GRUB features</a></li>
    <li><a name="toc-The-role-of-a-boot-loader" href="#Role-of-a-boot-loader">1.5 The role of a boot loader</a></li>
  </ul></li>
  <li><a name="toc-Naming-convention-1" href="#Naming-convention">2 Naming convention</a></li>
  <li><a name="toc-OS_002dspecific-notes-about-grub-tools-1" href="#OS_002dspecific-notes-about-grub-tools">3 OS-specific notes about grub tools</a></li>
  <li><a name="toc-Installation-1" href="#Installation">4 Installation</a>
  <ul class="no-bullet">
    <li><a name="toc-Installing-GRUB-using-grub2_002dinstall-1" href="#Installing-GRUB-using-grub2_002dinstall">4.1 Installing GRUB using grub2-install</a></li>
    <li><a name="toc-Making-a-GRUB-bootable-CD_002dROM-1" href="#Making-a-GRUB-bootable-CD_002dROM">4.2 Making a GRUB bootable CD-ROM</a></li>
    <li><a name="toc-The-map-between-BIOS-drives-and-OS-devices" href="#Device-map">4.3 The map between BIOS drives and OS devices</a></li>
    <li><a name="toc-BIOS-installation-1" href="#BIOS-installation">4.4 BIOS installation</a></li>
  </ul></li>
  <li><a name="toc-Booting-1" href="#Booting">5 Booting</a>
  <ul class="no-bullet">
    <li><a name="toc-How-to-boot-operating-systems" href="#General-boot-methods">5.1 How to boot operating systems</a>
    <ul class="no-bullet">
      <li><a name="toc-How-to-boot-an-OS-directly-with-GRUB" href="#Loading-an-operating-system-directly">5.1.1 How to boot an OS directly with GRUB</a></li>
      <li><a name="toc-Chain_002dloading-an-OS" href="#Chain_002dloading">5.1.2 Chain-loading an OS</a></li>
    </ul></li>
    <li><a name="toc-Loopback-booting-1" href="#Loopback-booting">5.2 Loopback booting</a></li>
    <li><a name="toc-Some-caveats-on-OS_002dspecific-issues" href="#OS_002dspecific-notes">5.3 Some caveats on OS-specific issues</a>
    <ul class="no-bullet">
      <li><a name="toc-GNU_002fHurd-1" href="#GNU_002fHurd">5.3.1 GNU/Hurd</a></li>
      <li><a name="toc-GNU_002fLinux-1" href="#GNU_002fLinux">5.3.2 GNU/Linux</a></li>
      <li><a name="toc-NetBSD-1" href="#NetBSD">5.3.3 NetBSD</a></li>
      <li><a name="toc-DOS_002fWindows-1" href="#DOS_002fWindows">5.3.4 DOS/Windows</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Writing-your-own-configuration-file" href="#Configuration">6 Writing your own configuration file</a>
  <ul class="no-bullet">
    <li><a name="toc-Simple-configuration-handling" href="#Simple-configuration">6.1 Simple configuration handling</a></li>
    <li><a name="toc-Root-Identifcation-Heuristics-1" href="#Root-Identifcation-Heuristics">6.2 Root Identifcation Heuristics</a></li>
    <li><a name="toc-Writing-full-configuration-files-directly" href="#Shell_002dlike-scripting">6.3 Writing full configuration files directly</a></li>
    <li><a name="toc-Multi_002dboot-manual-config-1" href="#Multi_002dboot-manual-config">6.4 Multi-boot manual config</a></li>
    <li><a name="toc-Embedding-a-configuration-file-into-GRUB" href="#Embedded-configuration">6.5 Embedding a configuration file into GRUB</a></li>
  </ul></li>
  <li><a name="toc-Theme-file-format-1" href="#Theme-file-format">7 Theme file format</a>
  <ul class="no-bullet">
    <li><a name="toc-Introduction-1" href="#Introduction-1">7.1 Introduction</a></li>
    <li><a name="toc-Theme-Elements" href="#Theme-Elements">7.2 Theme Elements</a>
    <ul class="no-bullet">
      <li><a name="toc-Colors" href="#Colors">7.2.1 Colors</a></li>
      <li><a name="toc-Fonts" href="#Fonts">7.2.2 Fonts</a></li>
      <li><a name="toc-Progress-Bar" href="#Progress-Bar">7.2.3 Progress Bar</a></li>
      <li><a name="toc-Circular-Progress-Indicator" href="#Circular-Progress-Indicator">7.2.4 Circular Progress Indicator</a></li>
      <li><a name="toc-Labels" href="#Labels">7.2.5 Labels</a></li>
      <li><a name="toc-Boot-Menu" href="#Boot-Menu">7.2.6 Boot Menu</a></li>
      <li><a name="toc-Styled-Boxes" href="#Styled-Boxes">7.2.7 Styled Boxes</a></li>
      <li><a name="toc-Creating-Styled-Box-Images" href="#Creating-Styled-Box-Images">7.2.8 Creating Styled Box Images</a></li>
    </ul></li>
    <li><a name="toc-Theme-File-Manual" href="#Theme-File-Manual">7.3 Theme File Manual</a>
    <ul class="no-bullet">
      <li><a name="toc-Global-Properties" href="#Global-Properties">7.3.1 Global Properties</a></li>
      <li><a name="toc-Format" href="#Format">7.3.2 Format</a></li>
      <li><a name="toc-Global-Property-List" href="#Global-Property-List">7.3.3 Global Property List</a></li>
      <li><a name="toc-Component-Construction" href="#Component-Construction">7.3.4 Component Construction</a></li>
      <li><a name="toc-Component-List" href="#Component-List">7.3.5 Component List</a></li>
      <li><a name="toc-Common-properties" href="#Common-properties">7.3.6 Common properties</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Booting-GRUB-from-the-network" href="#Network">8 Booting GRUB from the network</a></li>
  <li><a name="toc-Using-GRUB-via-a-serial-line" href="#Serial-terminal">9 Using GRUB via a serial line</a></li>
  <li><a name="toc-Using-GRUB-with-vendor-power_002don-keys" href="#Vendor-power_002don-keys">10 Using GRUB with vendor power-on keys</a></li>
  <li><a name="toc-GRUB-image-files" href="#Images">11 GRUB image files</a></li>
  <li><a name="toc-Core-image-size-limitation-1" href="#Core-image-size-limitation">12 Core image size limitation</a></li>
  <li><a name="toc-Filesystem-syntax-and-semantics" href="#Filesystem">13 Filesystem syntax and semantics</a>
  <ul class="no-bullet">
    <li><a name="toc-How-to-specify-devices" href="#Device-syntax">13.1 How to specify devices</a></li>
    <li><a name="toc-How-to-specify-files" href="#File-name-syntax">13.2 How to specify files</a></li>
    <li><a name="toc-How-to-specify-block-lists" href="#Block-list-syntax">13.3 How to specify block lists</a></li>
  </ul></li>
  <li><a name="toc-GRUB_0027s-user-interface" href="#Interface">14 GRUB&rsquo;s user interface</a>
  <ul class="no-bullet">
    <li><a name="toc-The-flexible-command_002dline-interface" href="#Command_002dline-interface">14.1 The flexible command-line interface</a></li>
    <li><a name="toc-The-simple-menu-interface" href="#Menu-interface">14.2 The simple menu interface</a></li>
    <li><a name="toc-Editing-a-menu-entry" href="#Menu-entry-editor">14.3 Editing a menu entry</a></li>
  </ul></li>
  <li><a name="toc-GRUB-environment-variables" href="#Environment">15 GRUB environment variables</a>
  <ul class="no-bullet">
    <li><a name="toc-Special-environment-variables-1" href="#Special-environment-variables">15.1 Special environment variables</a>
    <ul class="no-bullet">
      <li><a name="toc-biosnum-1" href="#biosnum">15.1.1 biosnum</a></li>
      <li><a name="toc-check_005fappended_005fsignatures-1" href="#check_005fappended_005fsignatures">15.1.2 check_appended_signatures</a></li>
      <li><a name="toc-check_005fsignatures-1" href="#check_005fsignatures">15.1.3 check_signatures</a></li>
      <li><a name="toc-chosen-1" href="#chosen">15.1.4 chosen</a></li>
      <li><a name="toc-cmdpath-1" href="#cmdpath">15.1.5 cmdpath</a></li>
      <li><a name="toc-color_005fhighlight-1" href="#color_005fhighlight">15.1.6 color_highlight</a></li>
      <li><a name="toc-color_005fnormal-1" href="#color_005fnormal">15.1.7 color_normal</a></li>
      <li><a name="toc-config_005fdirectory-1" href="#config_005fdirectory">15.1.8 config_directory</a></li>
      <li><a name="toc-config_005ffile-1" href="#config_005ffile">15.1.9 config_file</a></li>
      <li><a name="toc-debug-1" href="#debug">15.1.10 debug</a></li>
      <li><a name="toc-default-1" href="#default">15.1.11 default</a></li>
      <li><a name="toc-fallback-1" href="#fallback">15.1.12 fallback</a></li>
      <li><a name="toc-gfxmode-1" href="#gfxmode">15.1.13 gfxmode</a></li>
      <li><a name="toc-gfxpayload-1" href="#gfxpayload">15.1.14 gfxpayload</a></li>
      <li><a name="toc-gfxterm_005ffont-1" href="#gfxterm_005ffont">15.1.15 gfxterm_font</a></li>
      <li><a name="toc-grub_005fcpu-1" href="#grub_005fcpu">15.1.16 grub_cpu</a></li>
      <li><a name="toc-grub_005fplatform-1" href="#grub_005fplatform">15.1.17 grub_platform</a></li>
      <li><a name="toc-icondir-1" href="#icondir">15.1.18 icondir</a></li>
      <li><a name="toc-lang-1" href="#lang">15.1.19 lang</a></li>
      <li><a name="toc-locale_005fdir-1" href="#locale_005fdir">15.1.20 locale_dir</a></li>
      <li><a name="toc-menu_005fcolor_005fhighlight-1" href="#menu_005fcolor_005fhighlight">15.1.21 menu_color_highlight</a></li>
      <li><a name="toc-menu_005fcolor_005fnormal-1" href="#menu_005fcolor_005fnormal">15.1.22 menu_color_normal</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fboot_005ffile-1" href="#net_005f_003cinterface_003e_005fboot_005ffile">15.1.23 net_<var>&lt;interface&gt;</var>_boot_file</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fdhcp_005fserver_005fname-1" href="#net_005f_003cinterface_003e_005fdhcp_005fserver_005fname">15.1.24 net_<var>&lt;interface&gt;</var>_dhcp_server_name</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fdomain-1" href="#net_005f_003cinterface_003e_005fdomain">15.1.25 net_<var>&lt;interface&gt;</var>_domain</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fextensionspath-1" href="#net_005f_003cinterface_003e_005fextensionspath">15.1.26 net_<var>&lt;interface&gt;</var>_extensionspath</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fhostname-1" href="#net_005f_003cinterface_003e_005fhostname">15.1.27 net_<var>&lt;interface&gt;</var>_hostname</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fip-1" href="#net_005f_003cinterface_003e_005fip">15.1.28 net_<var>&lt;interface&gt;</var>_ip</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fmac-1" href="#net_005f_003cinterface_003e_005fmac">15.1.29 net_<var>&lt;interface&gt;</var>_mac</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005fnext_005fserver-1" href="#net_005f_003cinterface_003e_005fnext_005fserver">15.1.30 net_<var>&lt;interface&gt;</var>_next_server</a></li>
      <li><a name="toc-net_005f_003cinterface_003e_005frootpath-1" href="#net_005f_003cinterface_003e_005frootpath">15.1.31 net_<var>&lt;interface&gt;</var>_rootpath</a></li>
      <li><a name="toc-net_005fdefault_005finterface-1" href="#net_005fdefault_005finterface">15.1.32 net_default_interface</a></li>
      <li><a name="toc-net_005fdefault_005fip-1" href="#net_005fdefault_005fip">15.1.33 net_default_ip</a></li>
      <li><a name="toc-net_005fdefault_005fmac-1" href="#net_005fdefault_005fmac">15.1.34 net_default_mac</a></li>
      <li><a name="toc-net_005fdefault_005fserver-1" href="#net_005fdefault_005fserver">15.1.35 net_default_server</a></li>
      <li><a name="toc-pager-1" href="#pager">15.1.36 pager</a></li>
      <li><a name="toc-prefix-1" href="#prefix">15.1.37 prefix</a></li>
      <li><a name="toc-pxe_005fblksize-1" href="#pxe_005fblksize">15.1.38 pxe_blksize</a></li>
      <li><a name="toc-pxe_005fdefault_005fgateway-1" href="#pxe_005fdefault_005fgateway">15.1.39 pxe_default_gateway</a></li>
      <li><a name="toc-pxe_005fdefault_005fserver-1" href="#pxe_005fdefault_005fserver">15.1.40 pxe_default_server</a></li>
      <li><a name="toc-root-1" href="#root">15.1.41 root</a></li>
      <li><a name="toc-superusers-1" href="#superusers">15.1.42 superusers</a></li>
      <li><a name="toc-theme-1" href="#theme">15.1.43 theme</a></li>
      <li><a name="toc-timeout-1" href="#timeout">15.1.44 timeout</a></li>
      <li><a name="toc-timeout_005fstyle-1" href="#timeout_005fstyle">15.1.45 timeout_style</a></li>
    </ul></li>
    <li><a name="toc-The-GRUB-environment-block" href="#Environment-block">15.2 The GRUB environment block</a></li>
  </ul></li>
  <li><a name="toc-The-list-of-available-commands" href="#Commands">16 The list of available commands</a>
  <ul class="no-bullet">
    <li><a name="toc-The-list-of-commands-for-the-menu-only" href="#Menu_002dspecific-commands">16.1 The list of commands for the menu only</a>
    <ul class="no-bullet">
      <li><a name="toc-menuentry-1" href="#menuentry">16.1.1 menuentry</a></li>
      <li><a name="toc-submenu-1" href="#submenu">16.1.2 submenu</a></li>
    </ul></li>
    <li><a name="toc-The-list-of-general-commands" href="#General-commands">16.2 The list of general commands</a>
    <ul class="no-bullet">
      <li><a name="toc-serial-1" href="#serial">16.2.1 serial</a></li>
      <li><a name="toc-terminal_005finput-1" href="#terminal_005finput">16.2.2 terminal_input</a></li>
      <li><a name="toc-terminal_005foutput-1" href="#terminal_005foutput">16.2.3 terminal_output</a></li>
      <li><a name="toc-terminfo-1" href="#terminfo">16.2.4 terminfo</a></li>
    </ul></li>
    <li><a name="toc-The-list-of-command_002dline-and-menu-entry-commands" href="#Command_002dline-and-menu-entry-commands">16.3 The list of command-line and menu entry commands</a>
    <ul class="no-bullet">
      <li><a name="toc-_005b-1" href="#g_t_005b">16.3.1 [</a></li>
      <li><a name="toc-acpi-1" href="#acpi">16.3.2 acpi</a></li>
      <li><a name="toc-authenticate-1" href="#authenticate">16.3.3 authenticate</a></li>
      <li><a name="toc-background_005fcolor-1" href="#background_005fcolor">16.3.4 background_color</a></li>
      <li><a name="toc-background_005fimage-1" href="#background_005fimage">16.3.5 background_image</a></li>
      <li><a name="toc-badram-1" href="#badram">16.3.6 badram</a></li>
      <li><a name="toc-blocklist-1" href="#blocklist">16.3.7 blocklist</a></li>
      <li><a name="toc-boot-1" href="#boot">16.3.8 boot</a></li>
      <li><a name="toc-cat-1" href="#cat">16.3.9 cat</a></li>
      <li><a name="toc-chainloader-1" href="#chainloader">16.3.10 chainloader</a></li>
      <li><a name="toc-clear-1" href="#clear">16.3.11 clear</a></li>
      <li><a name="toc-cmosclean-1" href="#cmosclean">16.3.12 cmosclean</a></li>
      <li><a name="toc-cmosdump-1" href="#cmosdump">16.3.13 cmosdump</a></li>
      <li><a name="toc-cmostest-1" href="#cmostest">16.3.14 cmostest</a></li>
      <li><a name="toc-cmp-1" href="#cmp">16.3.15 cmp</a></li>
      <li><a name="toc-configfile-1" href="#configfile">16.3.16 configfile</a></li>
      <li><a name="toc-cpuid-1" href="#cpuid">16.3.17 cpuid</a></li>
      <li><a name="toc-crc-1" href="#crc">16.3.18 crc</a></li>
      <li><a name="toc-cryptomount-1" href="#cryptomount">16.3.19 cryptomount</a></li>
      <li><a name="toc-cutmem-1" href="#cutmem">16.3.20 cutmem</a></li>
      <li><a name="toc-date-1" href="#date">16.3.21 date</a></li>
      <li><a name="toc-devicetree-1" href="#devicetree">16.3.22 devicetree</a></li>
      <li><a name="toc-distrust-1" href="#distrust">16.3.23 distrust</a></li>
      <li><a name="toc-distrust_005fcertificate-1" href="#distrust_005fcertificate">16.3.24 distrust_certificate</a></li>
      <li><a name="toc-drivemap-1" href="#drivemap">16.3.25 drivemap</a></li>
      <li><a name="toc-echo-1" href="#echo">16.3.26 echo</a></li>
      <li><a name="toc-eval-1" href="#eval">16.3.27 eval</a></li>
      <li><a name="toc-export-1" href="#export">16.3.28 export</a></li>
      <li><a name="toc-false-1" href="#false">16.3.29 false</a></li>
      <li><a name="toc-gettext-1" href="#gettext">16.3.30 gettext</a></li>
      <li><a name="toc-gptsync-1" href="#gptsync">16.3.31 gptsync</a></li>
      <li><a name="toc-halt-1" href="#halt">16.3.32 halt</a></li>
      <li><a name="toc-hashsum-1" href="#hashsum">16.3.33 hashsum</a></li>
      <li><a name="toc-help-1" href="#help">16.3.34 help</a></li>
      <li><a name="toc-initrd-1" href="#initrd">16.3.35 initrd</a></li>
      <li><a name="toc-initrd16-1" href="#initrd16">16.3.36 initrd16</a></li>
      <li><a name="toc-insmod-1" href="#insmod">16.3.37 insmod</a></li>
      <li><a name="toc-keystatus-1" href="#keystatus">16.3.38 keystatus</a></li>
      <li><a name="toc-linux-1" href="#linux">16.3.39 linux</a></li>
      <li><a name="toc-linux16-1" href="#linux16">16.3.40 linux16</a></li>
      <li><a name="toc-list_005fcertificates-1" href="#list_005fcertificates">16.3.41 list_certificates</a></li>
      <li><a name="toc-list_005fenv-1" href="#list_005fenv">16.3.42 list_env</a></li>
      <li><a name="toc-list_005ftrusted-1" href="#list_005ftrusted">16.3.43 list_trusted</a></li>
      <li><a name="toc-load_005fenv-1" href="#load_005fenv">16.3.44 load_env</a></li>
      <li><a name="toc-loadfont-1" href="#loadfont">16.3.45 loadfont</a></li>
      <li><a name="toc-loopback-1" href="#loopback">16.3.46 loopback</a></li>
      <li><a name="toc-ls-1" href="#ls">16.3.47 ls</a></li>
      <li><a name="toc-lsfonts-1" href="#lsfonts">16.3.48 lsfonts</a></li>
      <li><a name="toc-lsmod-1" href="#lsmod">16.3.49 lsmod</a></li>
      <li><a name="toc-md5sum-1" href="#md5sum">16.3.50 md5sum</a></li>
      <li><a name="toc-module-1" href="#module">16.3.51 module</a></li>
      <li><a name="toc-multiboot-1" href="#multiboot">16.3.52 multiboot</a></li>
      <li><a name="toc-nativedisk-1" href="#nativedisk">16.3.53 nativedisk</a></li>
      <li><a name="toc-normal-1" href="#normal">16.3.54 normal</a></li>
      <li><a name="toc-normal_005fexit-1" href="#normal_005fexit">16.3.55 normal_exit</a></li>
      <li><a name="toc-parttool-1" href="#parttool">16.3.56 parttool</a></li>
      <li><a name="toc-password-1" href="#password">16.3.57 password</a></li>
      <li><a name="toc-password_005fpbkdf2-1" href="#password_005fpbkdf2">16.3.58 password_pbkdf2</a></li>
      <li><a name="toc-play-1" href="#play">16.3.59 play</a></li>
      <li><a name="toc-probe-1" href="#probe">16.3.60 probe</a></li>
      <li><a name="toc-pxe_005funload-1" href="#pxe_005funload">16.3.61 pxe_unload</a></li>
      <li><a name="toc-read-1" href="#read">16.3.62 read</a></li>
      <li><a name="toc-reboot-1" href="#reboot">16.3.63 reboot</a></li>
      <li><a name="toc-regexp-1" href="#regexp">16.3.64 regexp</a></li>
      <li><a name="toc-rmmod-1" href="#rmmod">16.3.65 rmmod</a></li>
      <li><a name="toc-save_005fenv-1" href="#save_005fenv">16.3.66 save_env</a></li>
      <li><a name="toc-search-1" href="#search">16.3.67 search</a></li>
      <li><a name="toc-sendkey-1" href="#sendkey">16.3.68 sendkey</a></li>
      <li><a name="toc-set-1" href="#set">16.3.69 set</a></li>
      <li><a name="toc-sha1sum-1" href="#sha1sum">16.3.70 sha1sum</a></li>
      <li><a name="toc-sha256sum-1" href="#sha256sum">16.3.71 sha256sum</a></li>
      <li><a name="toc-sha512sum-1" href="#sha512sum">16.3.72 sha512sum</a></li>
      <li><a name="toc-sleep-1" href="#sleep">16.3.73 sleep</a></li>
      <li><a name="toc-source-1" href="#source">16.3.74 source</a></li>
      <li><a name="toc-test-1" href="#test">16.3.75 test</a></li>
      <li><a name="toc-true-1" href="#true">16.3.76 true</a></li>
      <li><a name="toc-trust-1" href="#trust">16.3.77 trust</a></li>
      <li><a name="toc-trust_005fcertificate-1" href="#trust_005fcertificate">16.3.78 trust_certificate</a></li>
      <li><a name="toc-unset-1" href="#unset">16.3.79 unset</a></li>
      <li><a name="toc-uppermem-1" href="#uppermem">16.3.80 uppermem</a></li>
      <li><a name="toc-verify_005fappended-1" href="#verify_005fappended">16.3.81 verify_appended</a></li>
      <li><a name="toc-verify_005fdetached-1" href="#verify_005fdetached">16.3.82 verify_detached</a></li>
      <li><a name="toc-videoinfo-1" href="#videoinfo">16.3.83 videoinfo</a></li>
      <li><a name="toc-xen_005fhypervisor-1" href="#xen_005fhypervisor">16.3.84 xen_hypervisor</a></li>
      <li><a name="toc-xen_005fmodule-1" href="#xen_005fmodule">16.3.85 xen_module</a></li>
    </ul></li>
    <li><a name="toc-The-list-of-networking-commands" href="#Networking-commands">16.4 The list of networking commands</a>
    <ul class="no-bullet">
      <li><a name="toc-net_005fadd_005faddr-1" href="#net_005fadd_005faddr">16.4.1 net_add_addr</a></li>
      <li><a name="toc-net_005fadd_005fdns-1" href="#net_005fadd_005fdns">16.4.2 net_add_dns</a></li>
      <li><a name="toc-net_005fadd_005froute-1" href="#net_005fadd_005froute">16.4.3 net_add_route</a></li>
      <li><a name="toc-net_005fbootp-1" href="#net_005fbootp">16.4.4 net_bootp</a></li>
      <li><a name="toc-net_005fbootp6-1" href="#net_005fbootp6">16.4.5 net_bootp6</a></li>
      <li><a name="toc-net_005fdel_005faddr-1" href="#net_005fdel_005faddr">16.4.6 net_del_addr</a></li>
      <li><a name="toc-net_005fdel_005fdns-1" href="#net_005fdel_005fdns">16.4.7 net_del_dns</a></li>
      <li><a name="toc-net_005fdel_005froute-1" href="#net_005fdel_005froute">16.4.8 net_del_route</a></li>
      <li><a name="toc-net_005fget_005fdhcp_005foption-1" href="#net_005fget_005fdhcp_005foption">16.4.9 net_get_dhcp_option</a></li>
      <li><a name="toc-net_005fipv6_005fautoconf-1" href="#net_005fipv6_005fautoconf">16.4.10 net_ipv6_autoconf</a></li>
      <li><a name="toc-net_005fls_005faddr-1" href="#net_005fls_005faddr">16.4.11 net_ls_addr</a></li>
      <li><a name="toc-net_005fls_005fcards-1" href="#net_005fls_005fcards">16.4.12 net_ls_cards</a></li>
      <li><a name="toc-net_005fls_005fdns-1" href="#net_005fls_005fdns">16.4.13 net_ls_dns</a></li>
      <li><a name="toc-net_005fls_005froutes-1" href="#net_005fls_005froutes">16.4.14 net_ls_routes</a></li>
      <li><a name="toc-net_005fnslookup-1" href="#net_005fnslookup">16.4.15 net_nslookup</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Internationalisation-1" href="#Internationalisation">17 Internationalisation</a>
  <ul class="no-bullet">
    <li><a name="toc-Charset" href="#Charset">17.1 Charset</a></li>
    <li><a name="toc-Filesystems" href="#Filesystems">17.2 Filesystems</a></li>
    <li><a name="toc-Output-terminal" href="#Output-terminal">17.3 Output terminal</a></li>
    <li><a name="toc-Input-terminal" href="#Input-terminal">17.4 Input terminal</a></li>
    <li><a name="toc-Gettext" href="#Gettext">17.5 Gettext</a></li>
    <li><a name="toc-Regexp" href="#Regexp">17.6 Regexp</a></li>
    <li><a name="toc-Other" href="#Other">17.7 Other</a></li>
  </ul></li>
  <li><a name="toc-Security-1" href="#Security">18 Security</a>
  <ul class="no-bullet">
    <li><a name="toc-Authentication-and-authorisation-in-GRUB" href="#Authentication-and-authorisation">18.1 Authentication and authorisation in GRUB</a></li>
    <li><a name="toc-Using-GPG_002dstyle-digital-signatures-in-GRUB" href="#Using-GPG_002dstyle-digital-signatures">18.2 Using GPG-style digital signatures in GRUB</a></li>
    <li><a name="toc-Using-appended-signatures-in-GRUB" href="#Using-appended-signatures">18.3 Using appended signatures in GRUB</a></li>
    <li><a name="toc-Signing-GRUB-itself-1" href="#Signing-GRUB-itself">18.4 Signing GRUB itself</a></li>
    <li><a name="toc-Signing-GRUB-for-UEFI-secure-boot" href="#Signing-GRUB-for-UEFI-secure-boot">18.5 Signing GRUB for UEFI secure boot</a></li>
    <li><a name="toc-Signing-GRUB-with-an-appended-signature" href="#Signing-GRUB-with-an-appended-signature">18.6 Signing GRUB with an appended signature</a></li>
    <li><a name="toc-Embedded-information-for-generation-number-based-revocation" href="#Secure-Boot-Advanced-Targeting">18.7 Embedded information for generation number based revocation</a></li>
    <li><a name="toc-Lockdown-when-booting-on-a-secure-setup" href="#Lockdown">18.8 Lockdown when booting on a secure setup</a></li>
  </ul></li>
  <li><a name="toc-Platform-limitations-1" href="#Platform-limitations">19 Platform limitations</a></li>
  <li><a name="toc-Outline" href="#Platform_002dspecific-operations">20 Outline</a></li>
  <li><a name="toc-Supported-boot-targets" href="#Supported-kernels">21 Supported boot targets</a>
  <ul class="no-bullet">
    <li><a name="toc-Boot-tests" href="#Boot-tests">21.1 Boot tests</a></li>
  </ul></li>
  <li><a name="toc-Error-messages-produced-by-GRUB" href="#Troubleshooting">22 Error messages produced by GRUB</a>
  <ul class="no-bullet">
    <li><a name="toc-GRUB-only-offers-a-rescue-shell-1" href="#GRUB-only-offers-a-rescue-shell">22.1 GRUB only offers a rescue shell</a></li>
  </ul></li>
  <li><a name="toc-Invoking-grub2_002dinstall-1" href="#Invoking-grub2_002dinstall">23 Invoking grub2-install</a></li>
  <li><a name="toc-Invoking-grub2_002dmkconfig-1" href="#Invoking-grub2_002dmkconfig">24 Invoking grub2-mkconfig</a></li>
  <li><a name="toc-Invoking-grub2_002dmkpasswd_002dpbkdf2-1" href="#Invoking-grub2_002dmkpasswd_002dpbkdf2">25 Invoking grub2-mkpasswd-pbkdf2</a></li>
  <li><a name="toc-Invoking-grub2_002dmkrelpath-1" href="#Invoking-grub2_002dmkrelpath">26 Invoking grub2-mkrelpath</a></li>
  <li><a name="toc-Invoking-grub2_002dmkrescue-1" href="#Invoking-grub2_002dmkrescue">27 Invoking grub2-mkrescue</a></li>
  <li><a name="toc-Invoking-grub2_002dmount-1" href="#Invoking-grub2_002dmount">28 Invoking grub2-mount</a></li>
  <li><a name="toc-Invoking-grub2_002dprobe-1" href="#Invoking-grub2_002dprobe">29 Invoking grub2-probe</a></li>
  <li><a name="toc-Invoking-grub2_002dscript_002dcheck-1" href="#Invoking-grub2_002dscript_002dcheck">30 Invoking grub2-script-check</a></li>
  <li><a name="toc-How-to-obtain-and-build-GRUB" href="#Obtaining-and-Building-GRUB">Appendix A How to obtain and build GRUB</a></li>
  <li><a name="toc-Reporting-bugs-1" href="#Reporting-bugs">Appendix B Reporting bugs</a></li>
  <li><a name="toc-Where-GRUB-will-go" href="#Future">Appendix C Where GRUB will go</a></li>
  <li><a name="toc-Copying-This-Manual-1" href="#Copying-This-Manual">Appendix D Copying This Manual</a>
  <ul class="no-bullet">
    <li><a name="toc-GNU-Free-Documentation-License-1" href="#GNU-Free-Documentation-License">D.1 GNU Free Documentation License</a>
    <ul class="no-bullet">
      <li><a name="toc-ADDENDUM_003a-How-to-use-this-License-for-your-documents" href="#ADDENDUM_003a-How-to-use-this-License-for-your-documents">D.1.1 ADDENDUM: How to use this License for your documents</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Index-1" href="#Index">Index</a></li>
</ul>
</div>

<a name="Top"></a>
<div class="header">
<p>
Next: <a href="#Introduction" accesskey="n" rel="next">Introduction</a>, Up: <a href="dir.html#Top" accesskey="u" rel="up">(dir)</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GNU-GRUB-manual"></a>
<h1 class="top">GNU GRUB manual</h1>

<p>This is the documentation of GNU GRUB, the GRand Unified Bootloader,
a flexible and powerful boot loader program for a wide range of
architectures.
</p>
<p>This edition documents version 2.03.
</p>
<p>This manual is for GNU GRUB (version 2.03,
17 March 2026).
</p>
<p>Copyright &copy; 1999,2000,2001,2002,2004,2006,2008,2009,2010,2011,2012,2013 Free Software Foundation, Inc.
</p>
<blockquote>
<p>Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no
Invariant Sections.
</p></blockquote>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Introduction" accesskey="1">Introduction</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Capturing the spirit of GRUB
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Naming-convention" accesskey="2">Naming convention</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Names of your drives in GRUB
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#OS_002dspecific-notes-about-grub-tools" accesskey="3">OS-specific notes about grub tools</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
                                Some notes about OS-specific behaviour of GRUB
                                tools
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Installation" accesskey="4">Installation</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Installing GRUB on your drive
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Booting" accesskey="5">Booting</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">How to boot different operating systems
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Configuration" accesskey="6">Configuration</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Writing your own configuration file
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Theme-file-format" accesskey="7">Theme file format</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Format of GRUB theme files
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Network" accesskey="8">Network</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Downloading OS images from a network
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Serial-terminal" accesskey="9">Serial terminal</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Using GRUB via a serial line
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Vendor-power_002don-keys">Vendor power-on keys</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Changing GRUB behaviour on vendor power-on keys
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Images">Images</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">GRUB image files
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Core-image-size-limitation">Core image size limitation</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">GRUB image files size limitations
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Filesystem">Filesystem</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Filesystem syntax and semantics
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Interface">Interface</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The menu and the command-line
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Environment">Environment</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">GRUB environment variables
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Commands">Commands</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The list of available builtin commands
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Internationalisation">Internationalisation</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Topics relating to language support
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Security">Security</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Authentication, authorisation, and signatures
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Platform-limitations">Platform limitations</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The list of platform-specific limitations
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Platform_002dspecific-operations">Platform-specific operations</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Platform-specific operations
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Supported-kernels">Supported kernels</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The list of supported kernels
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Troubleshooting">Troubleshooting</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Error messages produced by GRUB
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dinstall">Invoking grub2-install</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">How to use the GRUB installer
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dmkconfig">Invoking grub2-mkconfig</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Generate a GRUB configuration file
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dmkpasswd_002dpbkdf2">Invoking grub2-mkpasswd-pbkdf2</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
                                Generate GRUB password hashes
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dmkrelpath">Invoking grub2-mkrelpath</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Make system path relative to its root
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dmkrescue">Invoking grub2-mkrescue</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Make a GRUB rescue image
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dmount">Invoking grub2-mount</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Mount a file system using GRUB
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dprobe">Invoking grub2-probe</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Probe device information for GRUB
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Invoking-grub2_002dscript_002dcheck">Invoking grub2-script-check</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Check GRUB script file for syntax errors
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Obtaining-and-Building-GRUB">Obtaining and Building GRUB</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">How to obtain and build GRUB
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Reporting-bugs">Reporting bugs</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Where you should send a bug report
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Future">Future</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Some future plans on GRUB
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Copying-This-Manual">Copying This Manual</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Copying This Manual
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Index">Index</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Introduction"></a>
<div class="header">
<p>
Next: <a href="#Naming-convention" accesskey="n" rel="next">Naming convention</a>, Previous: <a href="#Top" accesskey="p" rel="prev">Top</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Introduction-to-GRUB"></a>
<h2 class="chapter">1 Introduction to GRUB</h2>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Overview" accesskey="1">Overview</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">What exactly GRUB is and how to use it
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#History" accesskey="2">History</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">From maggot to house fly
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Changes-from-GRUB-Legacy" accesskey="3">Changes from GRUB Legacy</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Differences from previous versions
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Features" accesskey="4">Features</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">GRUB features
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Role-of-a-boot-loader" accesskey="5">Role of a boot loader</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The role of a boot loader
</td></tr>
</table>

<hr>
<a name="Overview"></a>
<div class="header">
<p>
Next: <a href="#History" accesskey="n" rel="next">History</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Overview-1"></a>
<h3 class="section">1.1 Overview</h3>

<p>Briefly, a <em>boot loader</em> is the first software program that runs when
a computer starts.  It is responsible for loading and transferring
control to an operating system <em>kernel</em> software (such as Linux or
GNU Mach).  The kernel, in turn, initializes the rest of the operating
system (e.g. a GNU system).
</p>
<p>GNU GRUB is a very powerful boot loader, which can load a wide variety
of free operating systems, as well as proprietary operating systems with
chain-loading<a name="DOCF1" href="#FOOT1"><sup>1</sup></a>. GRUB is designed to
address the complexity of booting a personal computer; both the
program and this manual are tightly bound to that computer platform,
although porting to other platforms may be addressed in the future.
</p>
<p>One of the important features in GRUB is flexibility; GRUB understands
filesystems and kernel executable formats, so you can load an arbitrary
operating system the way you like, without recording the physical
position of your kernel on the disk. Thus you can load the kernel
just by specifying its file name and the drive and partition where the
kernel resides.
</p>
<p>When booting with GRUB, you can use either a command-line interface
(see <a href="#Command_002dline-interface">Command-line interface</a>), or a menu interface (see <a href="#Menu-interface">Menu interface</a>). Using the command-line interface, you type the drive
specification and file name of the kernel manually. In the menu
interface, you just select an OS using the arrow keys. The menu is
based on a configuration file which you prepare beforehand
(see <a href="#Configuration">Configuration</a>). While in the menu, you can switch to the
command-line mode, and vice-versa. You can even edit menu entries
before using them.
</p>
<p>In the following chapters, you will learn how to specify a drive, a
partition, and a file name (see <a href="#Naming-convention">Naming convention</a>) to GRUB, how to
install GRUB on your drive (see <a href="#Installation">Installation</a>), and how to boot your
OSes (see <a href="#Booting">Booting</a>), step by step.
</p>

<hr>
<a name="History"></a>
<div class="header">
<p>
Next: <a href="#Changes-from-GRUB-Legacy" accesskey="n" rel="next">Changes from GRUB Legacy</a>, Previous: <a href="#Overview" accesskey="p" rel="prev">Overview</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="History-of-GRUB"></a>
<h3 class="section">1.2 History of GRUB</h3>

<p>GRUB originated in 1995 when Erich Boleyn was trying to boot the GNU
Hurd with the University of Utah&rsquo;s Mach 4 microkernel (now known as GNU
Mach).  Erich and Brian Ford designed the Multiboot Specification
(see <a href="http://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Top">Motivation</a> in <cite>The Multiboot
Specification</cite>), because they were determined not to add to the large
number of mutually-incompatible PC boot methods.
</p>
<p>Erich then began modifying the FreeBSD boot loader so that it would
understand Multiboot. He soon realized that it would be a lot easier
to write his own boot loader from scratch than to keep working on the
FreeBSD boot loader, and so GRUB was born.
</p>
<p>Erich added many features to GRUB, but other priorities prevented him
from keeping up with the demands of its quickly-expanding user base. In
1999, Gordon Matzigkeit and Yoshinori K. Okuji adopted GRUB as an
official GNU package, and opened its development by making the latest
sources available via anonymous CVS. See <a href="#Obtaining-and-Building-GRUB">Obtaining and Building GRUB</a>, for more information.
</p>
<p>Over the next few years, GRUB was extended to meet many needs, but it
quickly became clear that its design was not keeping up with the extensions
being made to it, and we reached the point where it was very difficult to
make any further changes without breaking existing features.  Around 2002,
Yoshinori K. Okuji started work on PUPA (Preliminary Universal Programming
Architecture for GNU GRUB), aiming to rewrite the core of GRUB to make it
cleaner, safer, more robust, and more powerful.  PUPA was eventually renamed
to GRUB 2, and the original version of GRUB was renamed to GRUB Legacy.
Small amounts of maintenance continued to be done on GRUB Legacy, but the
last release (0.97) was made in 2005 and at the time of writing it seems
unlikely that there will be another.
</p>
<p>By around 2007, GNU/Linux distributions started to use GRUB 2 to limited
extents, and by the end of 2009 multiple major distributions were installing
it by default.
</p>

<hr>
<a name="Changes-from-GRUB-Legacy"></a>
<div class="header">
<p>
Next: <a href="#Features" accesskey="n" rel="next">Features</a>, Previous: <a href="#History" accesskey="p" rel="prev">History</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Differences-from-previous-versions"></a>
<h3 class="section">1.3 Differences from previous versions</h3>

<p>GRUB 2 is a rewrite of GRUB (see <a href="#History">History</a>), although it shares many
characteristics with the previous version, now known as GRUB Legacy.  Users
of GRUB Legacy may need some guidance to find their way around this new
version.
</p>
<ul>
<li> The configuration file has a new name (<samp>grub.cfg</samp> rather than
<samp>menu.lst</samp> or <samp>grub.conf</samp>), new syntax (see <a href="#Configuration">Configuration</a>) and
many new commands (see <a href="#Commands">Commands</a>).  Configuration cannot be copied over
directly, although most GRUB Legacy users should not find the syntax too
surprising.

</li><li> <samp>grub.cfg</samp> is typically automatically generated by
<code>grub2-mkconfig</code> (see <a href="#Simple-configuration">Simple configuration</a>).  This makes it
easier to handle versioned kernel upgrades.

</li><li> Partition numbers in GRUB device names now start at 1, not 0 (see <a href="#Naming-convention">Naming convention</a>).

</li><li> The configuration file is now written in something closer to a full
scripting language: variables, conditionals, and loops are available.

</li><li> A small amount of persistent storage is available across reboots, using the
<code>save_env</code> and <code>load_env</code> commands in GRUB and the
<code>grub2-editenv</code> utility.  This is not available in all configurations
(see <a href="#Environment-block">Environment block</a>).

</li><li> GRUB 2 has more reliable ways to find its own files and those of target
kernels on multiple-disk systems, and has commands (see <a href="#search">search</a>) to find
devices using file system labels or Universally Unique Identifiers (UUIDs).

</li><li> GRUB 2 is available for several other types of system in addition to the PC
BIOS systems supported by GRUB Legacy: PC EFI, PC coreboot, PowerPC, SPARC,
and MIPS Lemote Yeeloong are all supported.

</li><li> Many more file systems are supported, including but not limited to ext4,
HFS+, and NTFS.

</li><li> GRUB 2 can read files directly from LVM and RAID devices.

</li><li> A graphical terminal and a graphical menu system are available.

</li><li> GRUB 2&rsquo;s interface can be translated, including menu entry names.

</li><li> The image files (see <a href="#Images">Images</a>) that make up GRUB have been reorganised;
Stage 1, Stage 1.5, and Stage 2 are no more.

</li><li> GRUB 2 puts many facilities in dynamically loaded modules, allowing the core
image to be smaller, and allowing the core image to be built in more
flexible ways.
</li></ul>

<hr>
<a name="Features"></a>
<div class="header">
<p>
Next: <a href="#Role-of-a-boot-loader" accesskey="n" rel="next">Role of a boot loader</a>, Previous: <a href="#Changes-from-GRUB-Legacy" accesskey="p" rel="prev">Changes from GRUB Legacy</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GRUB-features"></a>
<h3 class="section">1.4 GRUB features</h3>

<p>The primary requirement for GRUB is that it be compliant with the
<em>Multiboot Specification</em>, which is described in <a href="http://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Top">Motivation</a> in <cite>The Multiboot Specification</cite>.
</p>
<p>The other goals, listed in approximate order of importance, are:
</p>
<ul>
<li> Basic functions must be straightforward for end-users.

</li><li> Rich functionality to support kernel experts and designers.

</li><li> Backward compatibility for booting FreeBSD, NetBSD, OpenBSD, and
Linux. Proprietary kernels (such as DOS, Windows NT, and OS/2) are
supported via a chain-loading function.
</li></ul>

<p>Except for specific compatibility modes (chain-loading and the Linux
<em>piggyback</em> format), all kernels will be started in much the same
state as in the Multiboot Specification. Only kernels loaded at 1 megabyte
or above are presently supported. Any attempt to load below that
boundary will simply result in immediate failure and an error message
reporting the problem.
</p>
<p>In addition to the requirements above, GRUB has the following features
(note that the Multiboot Specification doesn&rsquo;t require all the features
that GRUB supports):
</p>
<dl compact="compact">
<dt>Recognize multiple executable formats</dt>
<dd><p>Support many of the <em>a.out</em> variants plus <em>ELF</em>. Symbol
tables are also loaded.
</p>
</dd>
<dt>Support non-Multiboot kernels</dt>
<dd><p>Support many of the various free 32-bit kernels that lack Multiboot
compliance (primarily FreeBSD, NetBSD<a name="DOCF2" href="#FOOT2"><sup>2</sup></a>,
OpenBSD, and Linux). Chain-loading of other boot loaders is also
supported.
</p>
</dd>
<dt>Load multiples modules</dt>
<dd><p>Fully support the Multiboot feature of loading multiple modules.
</p>
</dd>
<dt>Load a configuration file</dt>
<dd><p>Support a human-readable text configuration file with preset boot
commands. You can also load another configuration file dynamically and
embed a preset configuration file in a GRUB image file. The list of
commands (see <a href="#Commands">Commands</a>) are a superset of those supported on the
command-line. An example configuration file is provided in
<a href="#Configuration">Configuration</a>.
</p>
</dd>
<dt>Provide a menu interface</dt>
<dd><p>A menu interface listing preset boot commands, with a programmable
timeout, is available. There is no fixed limit on the number of boot
entries, and the current implementation has space for several hundred.
</p>
</dd>
<dt>Have a flexible command-line interface</dt>
<dd><p>A fairly flexible command-line interface, accessible from the menu,
is available to edit any preset commands, or write a new boot command
set from scratch. If no configuration file is present, GRUB drops to
the command-line.
</p>
<p>The list of commands (see <a href="#Commands">Commands</a>) are a subset of those supported
for configuration files. Editing commands closely resembles the Bash
command-line (see <a href="features.html#Command-Line-Editing">Command Line Editing</a> in <cite>Bash Features</cite>), with <tt class="key">TAB</tt>-completion of commands,
devices, partitions, and files in a directory depending on context.
</p>
</dd>
<dt>Support multiple filesystem types</dt>
<dd><p>Support multiple filesystem types transparently, plus a useful explicit
blocklist notation. The currently supported filesystem types are <em>Amiga
Fast FileSystem (AFFS)</em>, <em>AtheOS fs</em>, <em>BeFS</em>,
<em>BtrFS</em> (including raid0, raid1, raid10, gzip and lzo),
<em>cpio</em> (little- and big-endian bin, odc and newc variants),
<em>Linux ext2/ext3/ext4</em>, <em>DOS FAT12/FAT16/FAT32</em>,
<em>exFAT</em>, <em>F2FS</em>, <em>HFS</em>, <em>HFS+</em>,
<em>ISO9660</em> (including Joliet, Rock-ridge and multi-chunk files),
<em>JFS</em>, <em>Minix fs</em> (versions 1, 2 and 3), <em>nilfs2</em>,
<em>NTFS</em> (including compression), <em>ReiserFS</em>, <em>ROMFS</em>,
<em>Amiga Smart FileSystem (SFS)</em>, <em>Squash4</em>, <em>tar</em>, <em>UDF</em>,
<em>BSD UFS/UFS2</em>, <em>XFS</em>, and <em>ZFS</em> (including lzjb, gzip,
zle, mirror, stripe, raidz1/2/3 and encryption in AES-CCM and AES-GCM).
See <a href="#Filesystem">Filesystem</a>, for more information.
</p>
</dd>
<dt>Support automatic decompression</dt>
<dd><p>Can decompress files which were compressed by <code>gzip</code> or
<code>xz</code><a name="DOCF3" href="#FOOT3"><sup>3</sup></a>. This function is both automatic and transparent to the user
(i.e. all functions operate upon the uncompressed contents of the specified
files). This greatly reduces a file size and loading time, a
particularly great benefit for floppies.<a name="DOCF4" href="#FOOT4"><sup>4</sup></a>
</p>
<p>It is conceivable that some kernel modules should be loaded in a
compressed state, so a different module-loading command can be specified
to avoid uncompressing the modules.
</p>
</dd>
<dt>Access data on any installed device</dt>
<dd><p>Support reading data from any or all floppies or hard disk(s) recognized
by the BIOS, independent of the setting of the root device.
</p>
</dd>
<dt>Be independent of drive geometry translations</dt>
<dd><p>Unlike many other boot loaders, GRUB makes the particular drive
translation irrelevant. A drive installed and running with one
translation may be converted to another translation without any adverse
effects or changes in GRUB&rsquo;s configuration.
</p>
</dd>
<dt>Detect all installed <small>RAM</small></dt>
<dd><p>GRUB can generally find all the installed <small>RAM</small> on a PC-compatible
machine. It uses an advanced BIOS query technique for finding all
memory regions. As described on the Multiboot Specification (see <a href="http://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Top">Motivation</a> in <cite>The Multiboot
Specification</cite>), not all kernels make use of this information, but GRUB
provides it for those who do.
</p>
</dd>
<dt>Support Logical Block Address mode</dt>
<dd><p>In traditional disk calls (called <em>CHS mode</em>), there is a geometry
translation problem, that is, the BIOS cannot access over 1024
cylinders, so the accessible space is limited to at least 508 MB and to
at most 8GB. GRUB can&rsquo;t universally solve this problem, as there is no
standard interface used in all machines. However, several newer machines
have the new interface, Logical Block Address (<em>LBA</em>) mode. GRUB
automatically detects if LBA mode is available and uses it if
available. In LBA mode, GRUB can access the entire disk.
</p>
</dd>
<dt>Support network booting</dt>
<dd><p>GRUB is basically a disk-based boot loader but also has network
support. You can load OS images from a network by using the <em>TFTP</em>
protocol.
</p>
</dd>
<dt>Support remote terminals</dt>
<dd><p>To support computers with no console, GRUB provides remote terminal
support, so that you can control GRUB from a remote host. Only serial
terminal support is implemented at the moment.
</p></dd>
</dl>

<hr>
<a name="Role-of-a-boot-loader"></a>
<div class="header">
<p>
Previous: <a href="#Features" accesskey="p" rel="prev">Features</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="The-role-of-a-boot-loader"></a>
<h3 class="section">1.5 The role of a boot loader</h3>

<p>The following is a quotation from Gordon Matzigkeit, a GRUB fanatic:
</p>
<blockquote>
<p>Some people like to acknowledge both the operating system and kernel when
they talk about their computers, so they might say they use
&ldquo;GNU/Linux&rdquo; or &ldquo;GNU/Hurd&rdquo;.  Other people seem to think that the
kernel is the most important part of the system, so they like to call
their GNU operating systems &ldquo;Linux systems.&rdquo;
</p>
<p>I, personally, believe that this is a grave injustice, because the
<em>boot loader</em> is the most important software of all. I used to
refer to the above systems as either &ldquo;LILO&rdquo;<a name="DOCF5" href="#FOOT5"><sup>5</sup></a> or &ldquo;GRUB&rdquo;
systems.
</p>
<p>Unfortunately, nobody ever understood what I was talking about; now I
just use the word &ldquo;GNU&rdquo; as a pseudonym for GRUB.
</p>
<p>So, if you ever hear people talking about their alleged &ldquo;GNU&rdquo; systems,
remember that they are actually paying homage to the best boot loader
around&hellip; GRUB!
</p></blockquote>

<p>We, the GRUB maintainers, do not (usually) encourage Gordon&rsquo;s level of
fanaticism, but it helps to remember that boot loaders deserve
recognition.  We hope that you enjoy using GNU GRUB as much as we did
writing it.
</p>

<hr>
<a name="Naming-convention"></a>
<div class="header">
<p>
Next: <a href="#OS_002dspecific-notes-about-grub-tools" accesskey="n" rel="next">OS-specific notes about grub tools</a>, Previous: <a href="#Introduction" accesskey="p" rel="prev">Introduction</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Naming-convention-1"></a>
<h2 class="chapter">2 Naming convention</h2>

<p>The device syntax used in GRUB is a wee bit different from what you may
have seen before in your operating system(s), and you need to know it so
that you can specify a drive/partition.
</p>
<p>Look at the following examples and explanations:
</p>
<div class="example">
<pre class="example">(fd0)
</pre></div>

<p>First of all, GRUB requires that the device name be enclosed with
&lsquo;<samp>(</samp>&rsquo; and &lsquo;<samp>)</samp>&rsquo;. The &lsquo;<samp>fd</samp>&rsquo; part means that it is a floppy
disk. The number &lsquo;<samp>0</samp>&rsquo; is the drive number, which is counted from
<em>zero</em>. This expression means that GRUB will use the whole floppy
disk.
</p>
<div class="example">
<pre class="example">(hd0,msdos2)
</pre></div>

<p>Here, &lsquo;<samp>hd</samp>&rsquo; means it is a hard disk drive. The first integer
&lsquo;<samp>0</samp>&rsquo; indicates the drive number, that is, the first hard disk,
the string &lsquo;<samp>msdos</samp>&rsquo; indicates the partition scheme, while
the second integer, &lsquo;<samp>2</samp>&rsquo;, indicates the partition number (or the
<small>PC</small> slice number in the BSD terminology). The partition numbers are
counted from <em>one</em>, not from zero (as was the case in previous
versions of GRUB). This expression means the second partition of the
first hard disk drive. In this case, GRUB uses one partition of the
disk, instead of the whole disk.
</p>
<div class="example">
<pre class="example">(hd0,msdos5)
</pre></div>

<p>This specifies the first <em>extended partition</em> of the first hard disk
drive. Note that the partition numbers for extended partitions are
counted from &lsquo;<samp>5</samp>&rsquo;, regardless of the actual number of primary
partitions on your hard disk.
</p>
<div class="example">
<pre class="example">(hd1,msdos1,bsd1)
</pre></div>

<p>This means the BSD &lsquo;<samp>a</samp>&rsquo; partition on first <small>PC</small> slice number
of the second hard disk.
</p>
<p>Of course, to actually access the disks or partitions with GRUB, you
need to use the device specification in a command, like &lsquo;<samp>set
root=(fd0)</samp>&rsquo; or &lsquo;<samp>parttool (hd0,msdos3) hidden-</samp>&rsquo;. To help you find out
which number specifies a partition you want, the GRUB command-line
(see <a href="#Command_002dline-interface">Command-line interface</a>) options have argument
completion. This means that, for example, you only need to type
</p>
<div class="example">
<pre class="example">set root=(
</pre></div>

<p>followed by a <tt class="key">TAB</tt>, and GRUB will display the list of drives,
partitions, or file names. So it should be quite easy to determine the
name of your target partition, even with minimal knowledge of the
syntax.
</p>
<p>Note that GRUB does <em>not</em> distinguish IDE from SCSI - it simply
counts the drive numbers from zero, regardless of their type. Normally,
any IDE drive number is less than any SCSI drive number, although that
is not true if you change the boot sequence by swapping IDE and SCSI
drives in your BIOS.
</p>
<p>Now the question is, how to specify a file? Again, consider an
example:
</p>
<div class="example">
<pre class="example">(hd0,msdos1)/vmlinuz
</pre></div>

<p>This specifies the file named &lsquo;<samp>vmlinuz</samp>&rsquo;, found on the first
partition of the first hard disk drive. Note that the argument
completion works with file names, too.
</p>
<p>That was easy, admit it. Now read the next chapter, to find out how to
actually install GRUB on your drive.
</p>
<hr>
<a name="OS_002dspecific-notes-about-grub-tools"></a>
<div class="header">
<p>
Next: <a href="#Installation" accesskey="n" rel="next">Installation</a>, Previous: <a href="#Naming-convention" accesskey="p" rel="prev">Naming convention</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="OS_002dspecific-notes-about-grub-tools-1"></a>
<h2 class="chapter">3 OS-specific notes about grub tools</h2>

<p>On OS which have device nodes similar to Unix-like OS GRUB tools use the
OS name. E.g. for GNU/Linux:
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install /dev/sda</kbd>
</pre></div>

<p>On AROS we use another syntax. For volumes:
</p>
<div class="example">
<pre class="example">//:&lt;volume name&gt;
</pre></div>

<p>For disks we use syntax:
</p><div class="example">
<pre class="example">//:&lt;driver name&gt;/unit/flags
</pre></div>

<p>E.g.
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install //:ata.device/0/0</kbd>
</pre></div>

<p>On Windows we use UNC path. For volumes it&rsquo;s typically
</p>
<div class="example">
<pre class="example">\\?\Volume{&lt;GUID&gt;}
\\?\&lt;drive letter&gt;:
</pre></div>

<p>E.g.
</p>
<div class="example">
<pre class="example">\\?\Volume{17f34d50-cf64-4b02-800e-51d79c3aa2ff}
\\?\C:
</pre></div>

<p>For disks it&rsquo;s
</p>
<div class="example">
<pre class="example">\\?\PhysicalDrive&lt;number&gt;
</pre></div>

<p>E.g.
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install \\?\PhysicalDrive0</kbd>
</pre></div>

<p>Beware that you may need to further escape the backslashes depending on your
shell.
</p>
<p>When compiled with cygwin support then cygwin drive names are automatically
when needed. E.g.
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install /dev/sda</kbd>
</pre></div>

<hr>
<a name="Installation"></a>
<div class="header">
<p>
Next: <a href="#Booting" accesskey="n" rel="next">Booting</a>, Previous: <a href="#OS_002dspecific-notes-about-grub-tools" accesskey="p" rel="prev">OS-specific notes about grub tools</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Installation-1"></a>
<h2 class="chapter">4 Installation</h2>

<p>In order to install GRUB as your boot loader, you need to first
install the GRUB system and utilities under your UNIX-like operating
system (see <a href="#Obtaining-and-Building-GRUB">Obtaining and Building GRUB</a>). You can do this either
from the source tarball, or as a package for your OS.
</p>
<p>After you have done that, you need to install the boot loader on a
drive (floppy or hard disk) by using the utility
<code>grub2-install</code> (see <a href="#Invoking-grub2_002dinstall">Invoking grub2-install</a>) on a UNIX-like OS.
</p>
<p>GRUB comes with boot images, which are normally put in the directory
<samp>/usr/lib/grub/&lt;cpu&gt;-&lt;platform&gt;</samp> (for BIOS-based machines
<samp>/usr/lib/grub/i386-pc</samp>). Hereafter, the directory where GRUB images are
initially placed (normally <samp>/usr/lib/grub/&lt;cpu&gt;-&lt;platform&gt;</samp>) will be
called the <em>image directory</em>, and the directory where the boot
loader needs to find them (usually <samp>/boot</samp>) will be called
the <em>boot directory</em>.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Installing-GRUB-using-grub2_002dinstall" accesskey="1">Installing GRUB using grub2-install</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Making-a-GRUB-bootable-CD_002dROM" accesskey="2">Making a GRUB bootable CD-ROM</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Device-map" accesskey="3">Device map</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#BIOS-installation" accesskey="4">BIOS installation</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Installing-GRUB-using-grub2_002dinstall"></a>
<div class="header">
<p>
Next: <a href="#Making-a-GRUB-bootable-CD_002dROM" accesskey="n" rel="next">Making a GRUB bootable CD-ROM</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Installing-GRUB-using-grub2_002dinstall-1"></a>
<h3 class="section">4.1 Installing GRUB using grub2-install</h3>

<p>For information on where GRUB should be installed on PC BIOS platforms,
see <a href="#BIOS-installation">BIOS installation</a>.
</p>
<p>In order to install GRUB under a UNIX-like OS (such
as <small>GNU</small>), invoke the program <code>grub2-install</code> (see <a href="#Invoking-grub2_002dinstall">Invoking grub2-install</a>) as the superuser (<em>root</em>).
</p>
<p>The usage is basically very simple. You only need to specify one
argument to the program, namely, where to install the boot loader. The
argument has to be either a device file (like &lsquo;<samp>/dev/hda</samp>&rsquo;).
For example, under Linux the following will install GRUB into the MBR
of the first IDE disk:
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install /dev/sda</kbd>
</pre></div>

<p>Likewise, under GNU/Hurd, this has the same effect:
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install /dev/hd0</kbd>
</pre></div>

<p>But all the above examples assume that GRUB should put images under
the <samp>/boot</samp> directory. If you want GRUB to put images under a directory
other than <samp>/boot</samp>, you need to specify the option
<samp>--boot-directory</samp>. The typical usage is that you create a GRUB
boot floppy with a filesystem. Here is an example:
</p>
<div class="example">
<pre class="example"># <kbd>mke2fs /dev/fd0</kbd>
# <kbd>mount -t ext2 /dev/fd0 /mnt</kbd>
# <kbd>mkdir /mnt/boot</kbd>
# <kbd>grub2-install --boot-directory=/mnt/boot /dev/fd0</kbd>
# <kbd>umount /mnt</kbd>
</pre></div>

<p>Some BIOSes have a bug of exposing the first partition of a USB drive as a
floppy instead of exposing the USB drive as a hard disk (they call it
&ldquo;USB-FDD&rdquo; boot). In such cases, you need to install like this:
</p>
<div class="example">
<pre class="example"># <kbd>losetup /dev/loop0 /dev/sdb1</kbd>
# <kbd>mount /dev/loop0 /mnt/usb</kbd>
# <kbd>grub2-install --boot-directory=/mnt/usb/bugbios --force --allow-floppy /dev/loop0</kbd>
</pre></div>

<p>This install doesn&rsquo;t conflict with standard install as long as they are in
separate directories.
</p>
<p>On EFI systems for fixed disk install you have to mount EFI System Partition.
If you mount it at <samp>/boot/efi</samp> then you don&rsquo;t need any special arguments:
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install</kbd>
</pre></div>

<p>Otherwise you need to specify where your EFI System partition is mounted:
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install --efi-directory=/mnt/efi</kbd>
</pre></div>

<p>For removable installs you have to use <samp>--removable</samp> and specify both
<samp>--boot-directory</samp> and <samp>--efi-directory</samp>:
</p>
<div class="example">
<pre class="example"># <kbd>grub2-install --efi-directory=/mnt/usb --boot-directory=/mnt/usb/boot --removable</kbd>
</pre></div>

<hr>
<a name="Making-a-GRUB-bootable-CD_002dROM"></a>
<div class="header">
<p>
Next: <a href="#Device-map" accesskey="n" rel="next">Device map</a>, Previous: <a href="#Installing-GRUB-using-grub2_002dinstall" accesskey="p" rel="prev">Installing GRUB using grub2-install</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Making-a-GRUB-bootable-CD_002dROM-1"></a>
<h3 class="section">4.2 Making a GRUB bootable CD-ROM</h3>

<p>GRUB supports the <em>no emulation mode</em> in the El Torito
specification<a name="DOCF6" href="#FOOT6"><sup>6</sup></a>. This means that you can use the whole CD-ROM
from GRUB and you don&rsquo;t have to make a floppy or hard disk image file,
which can cause compatibility problems.
</p>
<p>For booting from a CD-ROM, GRUB uses a special image called
<samp>cdboot.img</samp>, which is concatenated with <samp>core.img</samp>. The
<samp>core.img</samp> used for this should be built with at least the
&lsquo;<samp>iso9660</samp>&rsquo; and &lsquo;<samp>biosdisk</samp>&rsquo; modules. Your bootable CD-ROM will
usually also need to include a configuration file <samp>grub.cfg</samp> and some
other GRUB modules.
</p>
<p>To make a simple generic GRUB rescue CD, you can use the
<code>grub2-mkrescue</code> program (see <a href="#Invoking-grub2_002dmkrescue">Invoking grub2-mkrescue</a>):
</p>
<div class="example">
<pre class="example">$ <kbd>grub2-mkrescue -o grub.iso</kbd>
</pre></div>

<p>You will often need to include other files in your image. To do this, first
make a top directory for the bootable image, say, &lsquo;<samp>iso</samp>&rsquo;:
</p>
<div class="example">
<pre class="example">$ <kbd>mkdir iso</kbd>
</pre></div>

<p>Make a directory for GRUB:
</p>
<div class="example">
<pre class="example">$ <kbd>mkdir -p iso/boot/grub</kbd>
</pre></div>

<p>If desired, make the config file <samp>grub.cfg</samp> under <samp>iso/boot/grub</samp>
(see <a href="#Configuration">Configuration</a>), and copy any files and directories for the disc to the
directory <samp>iso/</samp>.
</p>
<p>Finally, make the image:
</p>
<div class="example">
<pre class="example">$ <kbd>grub2-mkrescue -o grub.iso iso</kbd>
</pre></div>

<p>This produces a file named <samp>grub.iso</samp>, which then can be burned
into a CD (or a DVD), or written to a USB mass storage device.
</p>
<p>The root device will be set up appropriately on entering your
<samp>grub.cfg</samp> configuration file, so you can refer to file names on the CD
without needing to use an explicit device name. This makes it easier to
produce rescue images that will work on both optical drives and USB mass
storage devices.
</p>

<hr>
<a name="Device-map"></a>
<div class="header">
<p>
Next: <a href="#BIOS-installation" accesskey="n" rel="next">BIOS installation</a>, Previous: <a href="#Making-a-GRUB-bootable-CD_002dROM" accesskey="p" rel="prev">Making a GRUB bootable CD-ROM</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="The-map-between-BIOS-drives-and-OS-devices"></a>
<h3 class="section">4.3 The map between BIOS drives and OS devices</h3>

<p>If the device map file exists, the GRUB utilities (<code>grub2-probe</code>,
etc.) read it to map BIOS drives to OS devices.  This file consists of lines
like this:
</p>
<div class="example">
<pre class="example">(<var>device</var>) <var>file</var>
</pre></div>

<p><var>device</var> is a drive specified in the GRUB syntax (see <a href="#Device-syntax">Device syntax</a>), and <var>file</var> is an OS file, which is normally a device file.
</p>
<p>Historically, the device map file was used because GRUB device names had to
be used in the configuration file, and they were derived from BIOS drive
numbers.  The map between BIOS drives and OS devices cannot always be
guessed correctly: for example, GRUB will get the order wrong if you
exchange the boot sequence between IDE and SCSI in your BIOS.
</p>
<p>Unfortunately, even OS device names are not always stable.  Modern versions
of the Linux kernel may probe drives in a different order from boot to boot,
and the prefix (<samp>/dev/hd*</samp> versus <samp>/dev/sd*</samp>) may change depending
on the driver subsystem in use.  As a result, the device map file required
frequent editing on some systems.
</p>
<p>GRUB avoids this problem nowadays by using UUIDs or file system labels when
generating <samp>grub.cfg</samp>, and we advise that you do the same for any
custom menu entries you write.  If the device map file does not exist, then
the GRUB utilities will assume a temporary device map on the fly.  This is
often good enough, particularly in the common case of single-disk systems.
</p>
<p>However, the device map file is not entirely obsolete yet, and it is
used for overriding when current environment is different from the one on boot.
Most common case is if you use a partition or logical volume as a disk for
virtual machine.  You can put any comments in the file if needed,
as the GRUB utilities assume that a line is just a comment if
the first character is &lsquo;<samp>#</samp>&rsquo;.
</p>

<hr>
<a name="BIOS-installation"></a>
<div class="header">
<p>
Previous: <a href="#Device-map" accesskey="p" rel="prev">Device map</a>, Up: <a href="#Installation" accesskey="u" rel="up">Installation</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="BIOS-installation-1"></a>
<h3 class="section">4.4 BIOS installation</h3>

<p>The partition table format traditionally used on PC BIOS platforms is called
the Master Boot Record (MBR) format; this is the format that allows up to
four primary partitions and additional logical partitions.  With this
partition table format, there are two ways to install GRUB: it can be
embedded in the area between the MBR and the first partition (called by
various names, such as the &quot;boot track&quot;, &quot;MBR gap&quot;, or &quot;embedding area&quot;, and
which is usually at least 31 KiB), or the core image can be installed in a
file system and a list of the blocks that make it up can be stored in the
first sector of that partition.
</p>
<p>Each of these has different problems.  There is no way to reserve space in
the embedding area with complete safety, and some proprietary software is
known to use it to make it difficult for users to work around licensing
restrictions; and systems are sometimes partitioned without leaving enough
space before the first partition.  On the other hand, installing to a
filesystem means that GRUB is vulnerable to its blocks being moved around by
filesystem features such as tail packing, or even by aggressive fsck
implementations, so this approach is quite fragile; and this approach can
only be used if the <samp>/boot</samp> filesystem is on the same disk that the
BIOS boots from, so that GRUB does not have to rely on guessing BIOS drive
numbers.
</p>
<p>The GRUB development team generally recommends embedding GRUB before the
first partition, unless you have special requirements.  You must ensure that
the first partition starts at least 31 KiB (63 sectors) from the start of
the disk; on modern disks, it is often a performance advantage to align
partitions on larger boundaries anyway, so the first partition might start 1
MiB from the start of the disk.
</p>
<a name="GPT"></a>
<h3 class="heading">GPT</h3>

<p>Some newer systems use the GUID Partition Table (GPT) format.  This was
specified as part of the Extensible Firmware Interface (EFI), but it can
also be used on BIOS platforms if system software supports it; for example,
GRUB and GNU/Linux can be used in this configuration.  With this format, it
is possible to reserve a whole partition for GRUB, called the BIOS Boot
Partition.  GRUB can then be embedded into that partition without the risk
of being overwritten by other software and without being contained in a
filesystem which might move its blocks around.
</p>
<p>When creating a BIOS Boot Partition on a GPT system, you should make sure
that it is at least 31 KiB in size.  (GPT-formatted disks are not usually
particularly small, so we recommend that you make it larger than the bare
minimum, such as 1 MiB, to allow plenty of room for growth.)  You must also
make sure that it has the proper partition type.  Using GNU Parted, you can
set this using a command such as the following:
</p>
<div class="example">
<pre class="example"># <kbd>parted /dev/<var>disk</var> set <var>partition-number</var> bios_grub on</kbd>
</pre></div>

<p>If you are using gdisk, set the partition type to &lsquo;<samp>0xEF02</samp>&rsquo;.  With
partitioning programs that require setting the GUID directly, it should be
&lsquo;<samp>21686148-6449-6e6f-744e656564454649</samp>&rsquo;.
</p>
<p><strong>Caution:</strong> Be very careful which partition you select!  When GRUB
finds a BIOS Boot Partition during installation, it will automatically
overwrite part of it.  Make sure that the partition does not contain any
other data.
</p>

<hr>
<a name="Booting"></a>
<div class="header">
<p>
Next: <a href="#Configuration" accesskey="n" rel="next">Configuration</a>, Previous: <a href="#Installation" accesskey="p" rel="prev">Installation</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Booting-1"></a>
<h2 class="chapter">5 Booting</h2>

<p>GRUB can load Multiboot-compliant kernels in a consistent way,
but for some free operating systems you need to use some OS-specific
magic.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#General-boot-methods" accesskey="1">General boot methods</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">How to boot OSes with GRUB generally
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Loopback-booting" accesskey="2">Loopback booting</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Notes on booting from loopbacks
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#OS_002dspecific-notes" accesskey="3">OS-specific notes</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Notes on some operating systems
</td></tr>
</table>

<hr>
<a name="General-boot-methods"></a>
<div class="header">
<p>
Next: <a href="#Loopback-booting" accesskey="n" rel="next">Loopback booting</a>, Up: <a href="#Booting" accesskey="u" rel="up">Booting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="How-to-boot-operating-systems"></a>
<h3 class="section">5.1 How to boot operating systems</h3>

<p>GRUB has two distinct boot methods. One of the two is to load an
operating system directly, and the other is to chain-load another boot
loader which then will load an operating system actually. Generally
speaking, the former is more desirable, because you don&rsquo;t need to
install or maintain other boot loaders and GRUB is flexible enough to
load an operating system from an arbitrary disk/partition. However,
the latter is sometimes required, since GRUB doesn&rsquo;t support all the
existing operating systems natively.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Loading-an-operating-system-directly" accesskey="1">Loading an operating system directly</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Chain_002dloading" accesskey="2">Chain-loading</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Loading-an-operating-system-directly"></a>
<div class="header">
<p>
Next: <a href="#Chain_002dloading" accesskey="n" rel="next">Chain-loading</a>, Up: <a href="#General-boot-methods" accesskey="u" rel="up">General boot methods</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="How-to-boot-an-OS-directly-with-GRUB"></a>
<h4 class="subsection">5.1.1 How to boot an OS directly with GRUB</h4>

<p>Multiboot (see <a href="http://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Top">Motivation</a> in <cite>The Multiboot Specification</cite>) is the native format supported by GRUB.
For the sake of convenience, there is also support for Linux, FreeBSD,
NetBSD and OpenBSD. If you want to boot other operating systems, you
will have to chain-load them (see <a href="#Chain_002dloading">Chain-loading</a>).
</p>
<p>FIXME: this section is incomplete.
</p>
<ol>
<li> Run the command <code>boot</code> (see <a href="#boot">boot</a>).
</li></ol>

<p>However, DOS and Windows have some deficiencies, so you might have to
use more complicated instructions. See <a href="#DOS_002fWindows">DOS/Windows</a>, for more
information.
</p>

<hr>
<a name="Chain_002dloading"></a>
<div class="header">
<p>
Previous: <a href="#Loading-an-operating-system-directly" accesskey="p" rel="prev">Loading an operating system directly</a>, Up: <a href="#General-boot-methods" accesskey="u" rel="up">General boot methods</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Chain_002dloading-an-OS"></a>
<h4 class="subsection">5.1.2 Chain-loading an OS</h4>

<p>Operating systems that do not support Multiboot and do not have specific
support in GRUB (specific support is available for Linux, FreeBSD, NetBSD
and OpenBSD) must be chain-loaded, which involves loading another boot
loader and jumping to it in real mode.
</p>
<p>The <code>chainloader</code> command (see <a href="#chainloader">chainloader</a>) is used to set this
up.  It is normally also necessary to load some GRUB modules and set the
appropriate root device.  Putting this together, we get something like this,
for a Windows system on the first partition of the first hard disk:
</p>
<pre class="verbatim">menuentry &quot;Windows&quot; {
	insmod chain
	insmod ntfs
	set root=(hd0,1)
	chainloader +1
}
</pre>
<p>On systems with multiple hard disks, an additional workaround may be
required.  See <a href="#DOS_002fWindows">DOS/Windows</a>.
</p>
<p>Chain-loading is only supported on PC BIOS and EFI platforms.
</p>
<hr>
<a name="Loopback-booting"></a>
<div class="header">
<p>
Next: <a href="#OS_002dspecific-notes" accesskey="n" rel="next">OS-specific notes</a>, Previous: <a href="#General-boot-methods" accesskey="p" rel="prev">General boot methods</a>, Up: <a href="#Booting" accesskey="u" rel="up">Booting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Loopback-booting-1"></a>
<h3 class="section">5.2 Loopback booting</h3>
<p>GRUB is able to read from an image (be it one of CD or HDD) stored on
any of its accessible storages (refer to see <a href="#loopback">loopback</a> command).
However the OS itself should be able to find its root. This usually
involves running a userspace program running before the real root
is discovered. This is achieved by GRUB loading a specially made
small image and passing it as ramdisk to the kernel. This is achieved
by commands <code>kfreebsd_module</code>, <code>knetbsd_module_elf</code>,
<code>kopenbsd_ramdisk</code>, <code>initrd</code> (see <a href="#initrd">initrd</a>),
<code>initrd16</code> (see <a href="#initrd">initrd</a>), <code>multiboot_module</code>,
<code>multiboot2_module</code> or <code>xnu_ramdisk</code>
depending on the loader. Note that for knetbsd the image must be put
inside miniroot.kmod and the whole miniroot.kmod has to be loaded. In
kopenbsd payload this is disabled by default. Aditionally behaviour of
initial ramdisk depends on command line options. Several distributors provide
the image for this purpose or it&rsquo;s integrated in their standard ramdisk and
activated by special option. Consult your kernel and distribution manual for
more details. Other loaders like appleloader, chainloader (BIOS, EFI, coreboot),
freedos, ntldr and plan9 provide no possibility of loading initial ramdisk and
as far as author is aware the payloads in question don&rsquo;t support either initial
ramdisk or discovering loopback boot in other way and as such not bootable this
way. Please consider alternative boot methods like copying all files
from the image to actual partition. Consult your OS documentation for
more details
</p>
<hr>
<a name="OS_002dspecific-notes"></a>
<div class="header">
<p>
Previous: <a href="#Loopback-booting" accesskey="p" rel="prev">Loopback booting</a>, Up: <a href="#Booting" accesskey="u" rel="up">Booting</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Some-caveats-on-OS_002dspecific-issues"></a>
<h3 class="section">5.3 Some caveats on OS-specific issues</h3>

<p>Here, we describe some caveats on several operating systems.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#GNU_002fHurd" accesskey="1">GNU/Hurd</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#GNU_002fLinux" accesskey="2">GNU/Linux</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#NetBSD" accesskey="3">NetBSD</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#DOS_002fWindows" accesskey="4">DOS/Windows</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="GNU_002fHurd"></a>
<div class="header">
<p>
Next: <a href="#GNU_002fLinux" accesskey="n" rel="next">GNU/Linux</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">OS-specific notes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GNU_002fHurd-1"></a>
<h4 class="subsection">5.3.1 GNU/Hurd</h4>

<p>Since GNU/Hurd is Multiboot-compliant, it is easy to boot it; there is
nothing special about it. But do not forget that you have to specify a
root partition to the kernel.
</p>
<ol>
<li> Set GRUB&rsquo;s root device to the same drive as GNU/Hurd&rsquo;s.  The command
<code>search --set=root --file /boot/gnumach.gz</code> or similar may help you
(see <a href="#search">search</a>).

</li><li> Load the kernel and the modules, like this:

<div class="example">
<pre class="example">grub&gt; <kbd>multiboot /boot/gnumach.gz root=device:hd0s1</kbd>
grub&gt; <kbd>module  /hurd/ext2fs.static ext2fs --readonly \
                   --multiboot-command-line='${kernel-command-line}' \
                   --host-priv-port='${host-port}' \
                   --device-master-port='${device-port}' \
                   --exec-server-task='${exec-task}' -T typed '${root}' \
                   '$(task-create)' '$(task-resume)'</kbd>
grub&gt; <kbd>module /lib/ld.so.1 exec /hurd/exec '$(exec-task=task-create)'</kbd>
</pre></div>

</li><li> Finally, run the command <code>boot</code> (see <a href="#boot">boot</a>).
</li></ol>

<hr>
<a name="GNU_002fLinux"></a>
<div class="header">
<p>
Next: <a href="#NetBSD" accesskey="n" rel="next">NetBSD</a>, Previous: <a href="#GNU_002fHurd" accesskey="p" rel="prev">GNU/Hurd</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">OS-specific notes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GNU_002fLinux-1"></a>
<h4 class="subsection">5.3.2 GNU/Linux</h4>

<p>It is relatively easy to boot GNU/Linux from GRUB, because it somewhat
resembles to boot a Multiboot-compliant OS.
</p>
<ol>
<li> Set GRUB&rsquo;s root device to the same drive as GNU/Linux&rsquo;s.  The command
<code>search --set=root --file /vmlinuz</code> or similar may help you
(see <a href="#search">search</a>).

</li><li> Load the kernel using the command <code>linux</code> (see <a href="#linux">linux</a>):

<div class="example">
<pre class="example">grub&gt; <kbd>linux /vmlinuz root=/dev/sda1</kbd>
</pre></div>

<p>If you need to specify some kernel parameters, just append them to the
command.  For example, to set <samp>acpi</samp> to &lsquo;<samp>off</samp>&rsquo;, do this:
</p>
<div class="example">
<pre class="example">grub&gt; <kbd>linux /vmlinuz root=/dev/sda1 acpi=off</kbd>
</pre></div>

<p>See the documentation in the Linux source tree for complete information on
the available options.
</p>
<p>With <code>linux</code> GRUB uses 32-bit protocol. Some BIOS services like APM
or EDD aren&rsquo;t available with this protocol. In this case you need to use
<code>linux16</code>
</p>
<div class="example">
<pre class="example">grub&gt; <kbd>linux16 /vmlinuz root=/dev/sda1 acpi=off</kbd>
</pre></div>

</li><li> If you use an initrd, execute the command <code>initrd</code> (see <a href="#initrd">initrd</a>)
after <code>linux</code>:

<div class="example">
<pre class="example">grub&gt; <kbd>initrd /initrd</kbd>
</pre></div>

<p>If you used <code>linux16</code> you need to use <code>initrd16</code>:
</p>
<div class="example">
<pre class="example">grub&gt; <kbd>initrd16 /initrd</kbd>
</pre></div>

</li><li> Finally, run the command <code>boot</code> (see <a href="#boot">boot</a>).
</li></ol>

<p><strong>Caution:</strong> If you use an initrd and specify the &lsquo;<samp>mem=</samp>&rsquo;
option to the kernel to let it use less than actual memory size, you
will also have to specify the same memory size to GRUB. To let GRUB know
the size, run the command <code>uppermem</code> <em>before</em> loading the
kernel. See <a href="#uppermem">uppermem</a>, for more information.
</p>

<hr>
<a name="NetBSD"></a>
<div class="header">
<p>
Next: <a href="#DOS_002fWindows" accesskey="n" rel="next">DOS/Windows</a>, Previous: <a href="#GNU_002fLinux" accesskey="p" rel="prev">GNU/Linux</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">OS-specific notes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="NetBSD-1"></a>
<h4 class="subsection">5.3.3 NetBSD</h4>

<p>Booting a NetBSD kernel from GRUB is also relatively easy: first set
GRUB&rsquo;s root device, then load the kernel and the modules, and finally
run <code>boot</code>.
</p>
<ol>
<li> Set GRUB&rsquo;s root device to the partition holding the NetBSD root file
system.  For a disk with a NetBSD disk label, this is usually the first
partition (a:).  In that case, and assuming that the partition is on the
first hard disk, set GRUB&rsquo;s root device as follows:

<div class="example">
<pre class="example">grub&gt; <kbd>insmod part_bsd</kbd>
grub&gt; <kbd>set root=(hd0,netbsd1)</kbd>
</pre></div>

<p>For a disk with a GUID Partition Table (GPT), and assuming that the
NetBSD root partition is the third GPT partition, do this:
</p>
<div class="example">
<pre class="example">grub&gt; <kbd>insmod part_gpt</kbd>
grub&gt; <kbd>set root=(hd0,gpt3)</kbd>
</pre></div>

</li><li> Load the kernel using the command <code>knetbsd</code>:

<div class="example">
<pre class="example">grub&gt; <kbd>knetbsd /netbsd</kbd>
</pre></div>

<p>Various options may be given to <code>knetbsd</code>.  These options are,
for the most part, the same as in the NetBSD boot loader.  For instance,
to boot the system in single-user mode and with verbose messages, do
this:
</p>
<div class="example">
<pre class="example">grub&gt; <kbd>knetbsd /netbsd -s -v</kbd>
</pre></div>

</li><li> If needed, load kernel modules with the command
<code>knetbsd_module_elf</code>.  A typical example is the module for the
root file system:

<div class="example">
<pre class="example">grub&gt; <kbd>knetbsd_module_elf /stand/amd64/6.0/modules/ffs/ffs.kmod</kbd>
</pre></div>

</li><li> Finally, run the command <code>boot</code> (see <a href="#boot">boot</a>).
</li></ol>

<hr>
<a name="DOS_002fWindows"></a>
<div class="header">
<p>
Previous: <a href="#NetBSD" accesskey="p" rel="prev">NetBSD</a>, Up: <a href="#OS_002dspecific-notes" accesskey="u" rel="up">OS-specific notes</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="DOS_002fWindows-1"></a>
<h4 class="subsection">5.3.4 DOS/Windows</h4>

<p>GRUB cannot boot DOS or Windows directly, so you must chain-load them
(see <a href="#Chain_002dloading">Chain-loading</a>). However, their boot loaders have some critical
deficiencies, so it may not work to just chain-load them. To overcome
the problems, GRUB provides you with two helper functions.
</p>
<p>If you have installed DOS (or Windows) on a non-first hard disk, you
have to use the disk swapping technique, because that OS cannot boot
from any disks but the first one. The workaround used in GRUB is the
command <code>drivemap</code> (see <a href="#drivemap">drivemap</a>), like this:
</p>
<div class="example">
<pre class="example">drivemap -s (hd0) (hd1)
</pre></div>

<p>This performs a <em>virtual</em> swap between your first and second hard
drive.
</p>
<p><strong>Caution:</strong> This is effective only if DOS (or Windows) uses BIOS
to access the swapped disks. If that OS uses a special driver for the
disks, this probably won&rsquo;t work.
</p>
<p>Another problem arises if you installed more than one set of DOS/Windows
onto one disk, because they could be confused if there are more than one
primary partitions for DOS/Windows. Certainly you should avoid doing
this, but there is a solution if you do want to do so. Use the partition
hiding/unhiding technique.
</p>
<p>If GRUB <em>hides</em> a DOS (or Windows) partition (see <a href="#parttool">parttool</a>), DOS (or
Windows) will ignore the partition. If GRUB <em>unhides</em> a DOS (or Windows)
partition, DOS (or Windows) will detect the partition. Thus, if you have
installed DOS (or Windows) on the first and the second partition of the
first hard disk, and you want to boot the copy on the first partition, do
the following:
</p>
<div class="example">
<pre class="example">parttool (hd0,1) hidden-
parttool (hd0,2) hidden+
set root=(hd0,1)
chainloader +1
parttool <tt>${root}</tt> boot+
boot
</pre></div>

<hr>
<a name="Configuration"></a>
<div class="header">
<p>
Next: <a href="#Theme-file-format" accesskey="n" rel="next">Theme file format</a>, Previous: <a href="#Booting" accesskey="p" rel="prev">Booting</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Writing-your-own-configuration-file"></a>
<h2 class="chapter">6 Writing your own configuration file</h2>

<p>GRUB is configured using <samp>grub.cfg</samp>, usually located under
<samp>/boot/grub</samp>.  This file is quite flexible, but most users will not
need to write the whole thing by hand.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Simple-configuration" accesskey="1">Simple configuration</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Recommended for most users
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Root-Identifcation-Heuristics" accesskey="2">Root Identifcation Heuristics</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Summary on how the root file system is identified.
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Shell_002dlike-scripting" accesskey="3">Shell-like scripting</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">For power users and developers
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Multi_002dboot-manual-config" accesskey="4">Multi-boot manual config</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">For non-standard multi-OS scenarios
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Embedded-configuration" accesskey="5">Embedded configuration</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Embedding a configuration file into GRUB
</td></tr>
</table>

<hr>
<a name="Simple-configuration"></a>
<div class="header">
<p>
Next: <a href="#Root-Identifcation-Heuristics" accesskey="n" rel="next">Root Identifcation Heuristics</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Configuration</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Simple-configuration-handling"></a>
<h3 class="section">6.1 Simple configuration handling</h3>

<p>The program <code>grub2-mkconfig</code> (see <a href="#Invoking-grub2_002dmkconfig">Invoking grub2-mkconfig</a>)
generates <samp>grub.cfg</samp> files suitable for most cases.  It is suitable for
use when upgrading a distribution, and will discover available kernels and
attempt to generate menu entries for them.
</p>
<p><code>grub2-mkconfig</code> does have some limitations.  While adding extra
custom menu entries to the end of the list can be done by editing
<samp>/etc/grub.d/40_custom</samp> or creating <samp>/boot/grub2/custom.cfg</samp>,
changing the order of menu entries or changing their titles may require
making complex changes to shell scripts stored in <samp>/etc/grub.d/</samp>.  This
may be improved in the future.  In the meantime, those who feel that it
would be easier to write <samp>grub.cfg</samp> directly are encouraged to do so
(see <a href="#Booting">Booting</a>, and <a href="#Shell_002dlike-scripting">Shell-like scripting</a>), and to disable any system
provided by their distribution to automatically run <code>grub2-mkconfig</code>.
</p>
<p>The file <samp>/etc/default/grub</samp> controls the operation of
<code>grub2-mkconfig</code>.  It is sourced by a shell script, and so must be
valid POSIX shell input; normally, it will just be a sequence of
&lsquo;<samp>KEY=value</samp>&rsquo; lines, but if the value contains spaces or other special
characters then it must be quoted.  For example:
</p>
<div class="example">
<pre class="example">GRUB_TERMINAL_INPUT=&quot;console serial&quot;
</pre></div>

<p>Valid keys in <samp>/etc/default/grub</samp> are as follows:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>GRUB_DEFAULT</samp>&rsquo;</dt>
<dd><p>The default menu entry.  This may be a number, in which case it identifies
the Nth entry in the generated menu counted from zero, or the title of a
menu entry, or the special string &lsquo;<samp>saved</samp>&rsquo;.  Using the id may be
useful if you want to set a menu entry as the default even though there may
be a variable number of entries before it.
</p>
<p>For example, if you have:
</p>
<pre class="verbatim">menuentry 'Example GNU/Linux distribution' --class gnu-linux --id example-gnu-linux {
	...
}
</pre>
<p>then you can make this the default using:
</p>
<div class="example">
<pre class="example">GRUB_DEFAULT=example-gnu-linux
</pre></div>

<p>Previously it was documented the way to use entry title. While this still
works it&rsquo;s not recommended since titles often contain unstable device names
and may be translated
</p>
<p>If you set this to &lsquo;<samp>saved</samp>&rsquo;, then the default menu entry will be that
saved by &lsquo;<samp>GRUB_SAVEDEFAULT</samp>&rsquo; or <code>grub2-set-default</code>.  This relies on
the environment block, which may not be available in all situations
(see <a href="#Environment-block">Environment block</a>).
</p>
<p>The default is &lsquo;<samp>0</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_SAVEDEFAULT</samp>&rsquo;</dt>
<dd><p>If this option is set to &lsquo;<samp>true</samp>&rsquo;, then, when an entry is selected, save
it as a new default entry for use by future runs of GRUB.  This is only
useful if &lsquo;<samp>GRUB_DEFAULT=saved</samp>&rsquo;; it is a separate option because
&lsquo;<samp>GRUB_DEFAULT=saved</samp>&rsquo; is useful without this option, in conjunction with
<code>grub2-set-default</code>.  Unset by default.
This option relies on the environment block, which may not be available in
all situations (see <a href="#Environment-block">Environment block</a>).
</p>
</dd>
<dt>&lsquo;<samp>GRUB_TIMEOUT</samp>&rsquo;</dt>
<dd><p>Boot the default entry this many seconds after the menu is displayed, unless
a key is pressed.  The default is &lsquo;<samp>5</samp>&rsquo;.  Set to &lsquo;<samp>0</samp>&rsquo; to boot
immediately without displaying the menu, or to &lsquo;<samp>-1</samp>&rsquo; to wait
indefinitely.
</p>
<p>If &lsquo;<samp>GRUB_TIMEOUT_STYLE</samp>&rsquo; is set to &lsquo;<samp>countdown</samp>&rsquo; or &lsquo;<samp>hidden</samp>&rsquo;,
the timeout is instead counted before the menu is displayed.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_TIMEOUT_STYLE</samp>&rsquo;</dt>
<dd><p>If this option is unset or set to &lsquo;<samp>menu</samp>&rsquo;, then GRUB will display the
menu and then wait for the timeout set by &lsquo;<samp>GRUB_TIMEOUT</samp>&rsquo; to expire
before booting the default entry.  Pressing a key interrupts the timeout.
</p>
<p>If this option is set to &lsquo;<samp>countdown</samp>&rsquo; or &lsquo;<samp>hidden</samp>&rsquo;, then, before
displaying the menu, GRUB will wait for the timeout set by
&lsquo;<samp>GRUB_TIMEOUT</samp>&rsquo; to expire.  If <tt class="key">ESC</tt> is pressed during that time, it
will display the menu and wait for input.  If a hotkey associated with a
menu entry is pressed, it will boot the associated menu entry immediately.
If the timeout expires before either of these happens, it will boot the
default entry.  In the &lsquo;<samp>countdown</samp>&rsquo; case, it will show a one-line
indication of the remaining time.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_DEFAULT_BUTTON</samp>&rsquo;</dt>
<dt>&lsquo;<samp>GRUB_TIMEOUT_BUTTON</samp>&rsquo;</dt>
<dt>&lsquo;<samp>GRUB_TIMEOUT_STYLE_BUTTON</samp>&rsquo;</dt>
<dt>&lsquo;<samp>GRUB_BUTTON_CMOS_ADDRESS</samp>&rsquo;</dt>
<dd><p>Variants of the corresponding variables without the &lsquo;<samp>_BUTTON</samp>&rsquo; suffix,
used to support vendor-specific power buttons.  See <a href="#Vendor-power_002don-keys">Vendor power-on keys</a>.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_DISTRIBUTOR</samp>&rsquo;</dt>
<dd><p>Set by distributors of GRUB to their identifying name.  This is used to
generate more informative menu entry titles.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_TERMINAL_INPUT</samp>&rsquo;</dt>
<dd><p>Select the terminal input device.  You may select multiple devices here,
separated by spaces.
</p>
<p>Valid terminal input names depend on the platform, but may include
&lsquo;<samp>console</samp>&rsquo; (native platform console), &lsquo;<samp>serial</samp>&rsquo; (serial terminal),
&lsquo;<samp>serial_&lt;port&gt;</samp>&rsquo; (serial terminal with explicit port selection),
&lsquo;<samp>at_keyboard</samp>&rsquo; (PC AT keyboard), or &lsquo;<samp>usb_keyboard</samp>&rsquo; (USB keyboard
using the HID Boot Protocol, for cases where the firmware does not handle
this).
</p>
<p>The default is to use the platform&rsquo;s native terminal input.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_TERMINAL_OUTPUT</samp>&rsquo;</dt>
<dd><p>Select the terminal output device.  You may select multiple devices here,
separated by spaces.
</p>
<p>Valid terminal output names depend on the platform, but may include
&lsquo;<samp>console</samp>&rsquo; (native platform console), &lsquo;<samp>serial</samp>&rsquo; (serial terminal),
&lsquo;<samp>serial_&lt;port&gt;</samp>&rsquo; (serial terminal with explicit port selection),
&lsquo;<samp>gfxterm</samp>&rsquo; (graphics-mode output), &lsquo;<samp>vga_text</samp>&rsquo; (VGA text output),
&lsquo;<samp>mda_text</samp>&rsquo; (MDA text output), &lsquo;<samp>morse</samp>&rsquo; (Morse-coding using system
beeper) or &lsquo;<samp>spkmodem</samp>&rsquo; (simple data protocol using system speaker).
</p>
<p>&lsquo;<samp>spkmodem</samp>&rsquo; is useful when no serial port is available. Connect the output
of sending system (where GRUB is running) to line-in of receiving system
(usually developer machine).
On receiving system compile &lsquo;<samp>spkmodem-recv</samp>&rsquo; from
&lsquo;<samp>util/spkmodem-recv.c</samp>&rsquo; and run:
</p>
<div class="example">
<pre class="example">parecord --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv
</pre></div>

<p>The default is to use the platform&rsquo;s native terminal output.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_TERMINAL</samp>&rsquo;</dt>
<dd><p>If this option is set, it overrides both &lsquo;<samp>GRUB_TERMINAL_INPUT</samp>&rsquo; and
&lsquo;<samp>GRUB_TERMINAL_OUTPUT</samp>&rsquo; to the same value.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_SERIAL_COMMAND</samp>&rsquo;</dt>
<dd><p>A command to configure the serial port when using the serial console.
See <a href="#serial">serial</a>.  Defaults to &lsquo;<samp>serial</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_CMDLINE_LINUX</samp>&rsquo;</dt>
<dd><p>Command-line arguments to add to menu entries for the Linux kernel.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_CMDLINE_LINUX_DEFAULT</samp>&rsquo;</dt>
<dd><p>Unless &lsquo;<samp>GRUB_DISABLE_RECOVERY</samp>&rsquo; is set to &lsquo;<samp>true</samp>&rsquo;, two menu
entries will be generated for each Linux kernel: one default entry and one
entry for recovery mode.  This option lists command-line arguments to add
only to the default menu entry, after those listed in
&lsquo;<samp>GRUB_CMDLINE_LINUX</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_CMDLINE_NETBSD</samp>&rsquo;</dt>
<dt>&lsquo;<samp>GRUB_CMDLINE_NETBSD_DEFAULT</samp>&rsquo;</dt>
<dd><p>As &lsquo;<samp>GRUB_CMDLINE_LINUX</samp>&rsquo; and &lsquo;<samp>GRUB_CMDLINE_LINUX_DEFAULT</samp>&rsquo;, but for
NetBSD.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_CMDLINE_GNUMACH</samp>&rsquo;</dt>
<dd><p>As &lsquo;<samp>GRUB_CMDLINE_LINUX</samp>&rsquo;, but for GNU Mach.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_CMDLINE_XEN</samp>&rsquo;</dt>
<dt>&lsquo;<samp>GRUB_CMDLINE_XEN_DEFAULT</samp>&rsquo;</dt>
<dd><p>The values of these options are passed to Xen hypervisor Xen menu entries,
for all respectively normal entries.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_CMDLINE_LINUX_XEN_REPLACE</samp>&rsquo;</dt>
<dt>&lsquo;<samp>GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT</samp>&rsquo;</dt>
<dd><p>The values of these options replace the values of &lsquo;<samp>GRUB_CMDLINE_LINUX</samp>&rsquo;
and &lsquo;<samp>GRUB_CMDLINE_LINUX_DEFAULT</samp>&rsquo; for Linux and Xen menu entries.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_EARLY_INITRD_LINUX_CUSTOM</samp>&rsquo;</dt>
<dt>&lsquo;<samp>GRUB_EARLY_INITRD_LINUX_STOCK</samp>&rsquo;</dt>
<dd><p>List of space-separated early initrd images to be loaded from &lsquo;<samp>/boot</samp>&rsquo;.
This is for loading things like CPU microcode, firmware, ACPI tables, crypto
keys, and so on. These early images will be loaded in the order declared,
and all will be loaded before the actual functional initrd image.
</p>
<p>&lsquo;<samp>GRUB_EARLY_INITRD_LINUX_STOCK</samp>&rsquo; is for your distribution to declare
images that are provided by the distribution. It should not be modified
without understanding the consequences. They will be loaded first.
</p>
<p>&lsquo;<samp>GRUB_EARLY_INITRD_LINUX_CUSTOM</samp>&rsquo; is for your custom created images.
</p>
<p>The default stock images are as follows, though they may be overridden by
your distribution:
</p><div class="example">
<pre class="example">intel-uc.img intel-ucode.img amd-uc.img amd-ucode.img early_ucode.cpio microcode.cpio
</pre></div>

</dd>
<dt>&lsquo;<samp>GRUB_DISABLE_LINUX_UUID</samp>&rsquo;</dt>
<dd><p>Normally, <code>grub2-mkconfig</code> will generate menu entries that use
universally-unique identifiers (UUIDs) to identify the root filesystem to
the Linux kernel, using a &lsquo;<samp>root=UUID=...</samp>&rsquo; kernel parameter.  This is
usually more reliable, but in some cases it may not be appropriate.  To
disable the use of UUIDs, set this option to &lsquo;<samp>true</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo;</dt>
<dd><p>If <code>grub-mkconfig</code> cannot identify the root filesystem via its
universally-unique indentifier (UUID), <code>grub-mkconfig</code> can use the UUID
of the partition containing the filesystem to identify the root filesystem to
the Linux kernel via a &lsquo;<samp>root=PARTUUID=...</samp>&rsquo; kernel parameter.  This is not
as reliable as using the filesystem UUID, but is more reliable than using the
Linux device names. When &lsquo;<samp>GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; is set to
&lsquo;<samp>false</samp>&rsquo;, the Linux kernel version must be 2.6.37 (3.10 for systems using
the MSDOS partition scheme) or newer.  This option defaults to &lsquo;<samp>true</samp>&rsquo;.  To
enable the use of partition UUIDs, set this option to &lsquo;<samp>false</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_DISABLE_RECOVERY</samp>&rsquo;</dt>
<dd><p>If this option is set to &lsquo;<samp>true</samp>&rsquo;, disable the generation of recovery
mode menu entries.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_DISABLE_UUID</samp>&rsquo;</dt>
<dd><p>Normally, <code>grub2-mkconfig</code> will generate menu entries that use
universally-unique identifiers (UUIDs) to identify various filesystems to
search for files.  This is usually more reliable, but in some cases it may
not be appropriate.  To disable this use of UUIDs, set this option to
&lsquo;<samp>true</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_VIDEO_BACKEND</samp>&rsquo;</dt>
<dd><p>If graphical video support is required, either because the &lsquo;<samp>gfxterm</samp>&rsquo;
graphical terminal is in use or because &lsquo;<samp>GRUB_GFXPAYLOAD_LINUX</samp>&rsquo; is set,
then <code>grub2-mkconfig</code> will normally load all available GRUB video
drivers and use the one most appropriate for your hardware.  If you need to
override this for some reason, then you can set this option.
</p>
<p>After <code>grub2-install</code> has been run, the available video drivers are
listed in <samp>/boot/grub2/video.lst</samp>.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_GFXMODE</samp>&rsquo;</dt>
<dd><p>Set the resolution used on the &lsquo;<samp>gfxterm</samp>&rsquo; graphical terminal.  Note that
you can only use modes which your graphics card supports via VESA BIOS
Extensions (VBE), so for example native LCD panel resolutions may not be
available.  The default is &lsquo;<samp>auto</samp>&rsquo;, which tries to select a preferred
resolution.  See <a href="#gfxmode">gfxmode</a>.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_BACKGROUND</samp>&rsquo;</dt>
<dd><p>Set a background image for use with the &lsquo;<samp>gfxterm</samp>&rsquo; graphical terminal.
The value of this option must be a file readable by GRUB at boot time, and
it must end with <samp>.png</samp>, <samp>.tga</samp>, <samp>.jpg</samp>, or <samp>.jpeg</samp>.
The image will be scaled if necessary to fit the screen.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_THEME</samp>&rsquo;</dt>
<dd><p>Set a theme for use with the &lsquo;<samp>gfxterm</samp>&rsquo; graphical terminal.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_GFXPAYLOAD_LINUX</samp>&rsquo;</dt>
<dd><p>Set to &lsquo;<samp>text</samp>&rsquo; to force the Linux kernel to boot in normal text mode,
&lsquo;<samp>keep</samp>&rsquo; to preserve the graphics mode set using &lsquo;<samp>GRUB_GFXMODE</samp>&rsquo;,
&lsquo;<samp><var>width</var>x<var>height</var></samp>&rsquo;[&lsquo;<samp>x<var>depth</var></samp>&rsquo;] to set a particular
graphics mode, or a sequence of these separated by commas or semicolons to
try several modes in sequence.  See <a href="#gfxpayload">gfxpayload</a>.
</p>
<p>Depending on your kernel, your distribution, your graphics card, and the
phase of the moon, note that using this option may cause GNU/Linux to suffer
from various display problems, particularly during the early part of the
boot sequence.  If you have problems, set this option to &lsquo;<samp>text</samp>&rsquo; and
GRUB will tell Linux to boot in normal text mode.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_DISABLE_OS_PROBER</samp>&rsquo;</dt>
<dd><p>Normally, <code>grub2-mkconfig</code> will try to use the external
<code>os-prober</code> program, if installed, to discover other operating
systems installed on the same system and generate appropriate menu entries
for them.  Set this option to &lsquo;<samp>true</samp>&rsquo; to disable this.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_OS_PROBER_SKIP_LIST</samp>&rsquo;</dt>
<dd><p>List of space-separated FS UUIDs of filesystems to be ignored from os-prober
output. For efi chainloaders it&rsquo;s &lt;UUID&gt;@&lt;EFI FILE&gt;
</p>
</dd>
<dt>&lsquo;<samp>GRUB_DISABLE_SUBMENU</samp>&rsquo;</dt>
<dd><p>Normally, <code>grub2-mkconfig</code> will generate top level menu entry for
the kernel with highest version number and put all other found kernels
or alternative menu entries for recovery mode in submenu. For entries returned
by <code>os-prober</code> first entry will be put on top level and all others
in submenu. If this option is set to &lsquo;<samp>y</samp>&rsquo;, flat menu with all entries
on top level will be generated instead. Changing this option will require
changing existing values of &lsquo;<samp>GRUB_DEFAULT</samp>&rsquo;, &lsquo;<samp>fallback</samp>&rsquo; (see <a href="#fallback">fallback</a>)
and &lsquo;<samp>default</samp>&rsquo; (see <a href="#default">default</a>) environment variables as well as saved
default entry using <code>grub2-set-default</code> and value used with
<code>grub2-reboot</code>.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_ENABLE_CRYPTODISK</samp>&rsquo;</dt>
<dd><p>If set to &lsquo;<samp>y</samp>&rsquo;, <code>grub2-mkconfig</code> and <code>grub2-install</code> will
check for encrypted disks and generate additional commands needed to access
them during boot.  Note that in this case unattended boot is not possible
because GRUB will wait for passphrase to unlock encrypted container.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_INIT_TUNE</samp>&rsquo;</dt>
<dd><p>Play a tune on the speaker when GRUB starts.  This is particularly useful
for users unable to see the screen.  The value of this option is passed
directly to <a href="#play">play</a>.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_BADRAM</samp>&rsquo;</dt>
<dd><p>If this option is set, GRUB will issue a <a href="#badram">badram</a> command to filter
out specified regions of RAM.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_PRELOAD_MODULES</samp>&rsquo;</dt>
<dd><p>This option may be set to a list of GRUB module names separated by spaces.
Each module will be loaded as early as possible, at the start of
<samp>grub.cfg</samp>.
</p>
</dd>
</dl>

<p>The following options are still accepted for compatibility with existing
configurations, but have better replacements:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>GRUB_HIDDEN_TIMEOUT</samp>&rsquo;</dt>
<dd><p>Wait this many seconds before displaying the menu.  If <tt class="key">ESC</tt> is pressed
during that time, display the menu and wait for input according to
&lsquo;<samp>GRUB_TIMEOUT</samp>&rsquo;.  If a hotkey associated with a menu entry is pressed,
boot the associated menu entry immediately.  If the timeout expires before
either of these happens, display the menu for the number of seconds
specified in &lsquo;<samp>GRUB_TIMEOUT</samp>&rsquo; before booting the default entry.
</p>
<p>If you set &lsquo;<samp>GRUB_HIDDEN_TIMEOUT</samp>&rsquo;, you should also set
&lsquo;<samp>GRUB_TIMEOUT=0</samp>&rsquo; so that the menu is not displayed at all unless
<tt class="key">ESC</tt> is pressed.
</p>
<p>This option is unset by default, and is deprecated in favour of the less
confusing &lsquo;<samp>GRUB_TIMEOUT_STYLE=countdown</samp>&rsquo; or
&lsquo;<samp>GRUB_TIMEOUT_STYLE=hidden</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_HIDDEN_TIMEOUT_QUIET</samp>&rsquo;</dt>
<dd><p>In conjunction with &lsquo;<samp>GRUB_HIDDEN_TIMEOUT</samp>&rsquo;, set this to &lsquo;<samp>true</samp>&rsquo; to
suppress the verbose countdown while waiting for a key to be pressed before
displaying the menu.
</p>
<p>This option is unset by default, and is deprecated in favour of the less
confusing &lsquo;<samp>GRUB_TIMEOUT_STYLE=countdown</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>GRUB_HIDDEN_TIMEOUT_BUTTON</samp>&rsquo;</dt>
<dd><p>Variant of &lsquo;<samp>GRUB_HIDDEN_TIMEOUT</samp>&rsquo;, used to support vendor-specific power
buttons.  See <a href="#Vendor-power_002don-keys">Vendor power-on keys</a>.
</p>
<p>This option is unset by default, and is deprecated in favour of the less
confusing &lsquo;<samp>GRUB_TIMEOUT_STYLE=countdown</samp>&rsquo; or
&lsquo;<samp>GRUB_TIMEOUT_STYLE=hidden</samp>&rsquo;.
</p>
</dd>
</dl>

<p>For more detailed customisation of <code>grub2-mkconfig</code>&rsquo;s output, you may
edit the scripts in <samp>/etc/grub.d</samp> directly.
<samp>/etc/grub.d/40_custom</samp> is particularly useful for adding entire custom
menu entries; simply type the menu entries you want to add at the end of
that file, making sure to leave at least the first two lines intact.
</p>
<hr>
<a name="Root-Identifcation-Heuristics"></a>
<div class="header">
<p>
Next: <a href="#Shell_002dlike-scripting" accesskey="n" rel="next">Shell-like scripting</a>, Previous: <a href="#Simple-configuration" accesskey="p" rel="prev">Simple configuration</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Configuration</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Root-Identifcation-Heuristics-1"></a>
<h3 class="section">6.2 Root Identifcation Heuristics</h3>
<p>If the target operating system uses the Linux kernel, <code>grub-mkconfig</code>
attempts to identify the root file system via a heuristic algoirthm.  This
algorithm selects the identification method of the root file system by
considering three factors.  The first is if an initrd for the target operating
system is also present.  The second is &lsquo;<samp>GRUB_DISABLE_LINUX_UUID</samp>&rsquo; and if set
to &lsquo;<samp>true</samp>&rsquo;, prevents <code>grub-mkconfig</code> from identifying the root file
system by its UUID.  The third is &lsquo;<samp>GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; and if set
to &lsquo;<samp>true</samp>&rsquo;, prevents <code>grub-mkconfig</code> from identifying the root file
system via the UUID of its enclosing partition.  If the variables are assigned
any other value, that value is considered equivalent to &lsquo;<samp>false</samp>&rsquo;.  The
variables are also considered to be set to &lsquo;<samp>false</samp>&rsquo; if they are not set.
</p>
<p>When booting, the Linux kernel will delegate the task of mounting the root
filesystem to the initrd.  Most initrd images determine the root file system by
checking the Linux kernel&rsquo;s command-line for the &lsquo;<samp>root</samp>&rsquo; key and use its
value as the identification method of the root file system.  To improve the
reliability of booting, most initrd images also allow the root file system to be
identified by its UUID.  Because of this behavior, the <code>grub-mkconfig</code>
command will set &lsquo;<samp>root</samp>&rsquo; to &lsquo;<samp>root=UUID=...</samp>&rsquo; to provide the initrd with
the filesystem UUID of the root file system.
</p>
<p>If no initrd is detected or &lsquo;<samp>GRUB_DISABLE_LINUX_UUID</samp>&rsquo; is set to &lsquo;<samp>true</samp>&rsquo;
then <code>grub-command</code> will identify the root filesystem by setting the
kernel command-line variable &lsquo;<samp>root</samp>&rsquo; to &lsquo;<samp>root=PARTUUID=...</samp>&rsquo; unless
&lsquo;<samp>GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; is also set to &lsquo;<samp>true</samp>&rsquo;.  If
&lsquo;<samp>GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; is also set to &lsquo;<samp>true</samp>&rsquo;,
<code>grub-command</code> will identify by its Linux device name.
</p>
<p>The following table summarizes the behavior of the <code>grub-mkconfig</code>
command.
</p>
<table>
<thead><tr><th>Initrd detected</th><th>GRUB_DISABLE_LINUX_PARTUUID Set To</th><th>GRUB_DISABLE_LINUX_UUID Set To</th><th>Linux Root ID Method</th></tr></thead>
<tr><td>false</td><td>false</td><td>false</td><td>part UUID</td></tr>
<tr><td>false</td><td>false</td><td>true</td><td>part UUID</td></tr>
<tr><td>false</td><td>true</td><td>false</td><td>dev name</td></tr>
<tr><td>false</td><td>true</td><td>true</td><td>dev name</td></tr>
<tr><td>true</td><td>false</td><td>false</td><td>fs UUID</td></tr>
<tr><td>true</td><td>false</td><td>true</td><td>part UUID</td></tr>
<tr><td>true</td><td>true</td><td>false</td><td>fs UUID</td></tr>
<tr><td>true</td><td>true</td><td>true</td><td>dev name</td></tr>
</table>

<p>Remember, &lsquo;<samp>GRUB_DISABLE_LINUX_PARTUUID</samp>&rsquo; and &lsquo;<samp>GRUB_DISABLE_LINUX_UUID</samp>&rsquo;
are also considered to be set to &lsquo;<samp>false</samp>&rsquo; when they are unset.
</p>
<hr>
<a name="Shell_002dlike-scripting"></a>
<div class="header">
<p>
Next: <a href="#Multi_002dboot-manual-config" accesskey="n" rel="next">Multi-boot manual config</a>, Previous: <a href="#Root-Identifcation-Heuristics" accesskey="p" rel="prev">Root Identifcation Heuristics</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Configuration</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Writing-full-configuration-files-directly"></a>
<h3 class="section">6.3 Writing full configuration files directly</h3>

<p><samp>grub.cfg</samp> is written in GRUB&rsquo;s built-in scripting language, which has
a syntax quite similar to that of GNU Bash and other Bourne shell
derivatives.
</p>
<a name="Words"></a>
<h3 class="heading">Words</h3>

<p>A <em>word</em> is a sequence of characters considered as a single unit by
GRUB.  Words are separated by <em>metacharacters</em>, which are the following
plus space, tab, and newline:
</p>
<div class="example">
<pre class="example">{ } | &amp; $ ; &lt; &gt;
</pre></div>
 
<p>Quoting may be used to include metacharacters in words; see below.
</p>
<a name="Reserved-words"></a>
<h3 class="heading">Reserved words</h3>

<p>Reserved words have a special meaning to GRUB.  The following words are
recognised as reserved when unquoted and either the first word of a simple
command or the third word of a <code>for</code> command:
</p>
<div class="example">
<pre class="example">! [[ ]] { }
case do done elif else esac fi for function
if in menuentry select then time until while
</pre></div>

<p>Not all of these reserved words have a useful purpose yet; some are reserved
for future expansion.
</p>
<a name="Quoting"></a>
<h3 class="heading">Quoting</h3>

<p>Quoting is used to remove the special meaning of certain characters or
words.  It can be used to treat metacharacters as part of a word, to prevent
reserved words from being recognised as such, and to prevent variable
expansion.
</p>
<p>There are three quoting mechanisms: the escape character, single quotes, and
double quotes.
</p>
<p>A non-quoted backslash (\) is the <em>escape character</em>.  It preserves the
literal value of the next character that follows, with the exception of
newline.
</p>
<p>Enclosing characters in single quotes preserves the literal value of each
character within the quotes.  A single quote may not occur between single
quotes, even when preceded by a backslash.
</p>
<p>Enclosing characters in double quotes preserves the literal value of all
characters within the quotes, with the exception of &lsquo;<samp>$</samp>&rsquo; and &lsquo;<samp>\</samp>&rsquo;.
The &lsquo;<samp>$</samp>&rsquo; character retains its special meaning within double quotes.
The backslash retains its special meaning only when followed by one of the
following characters: &lsquo;<samp>$</samp>&rsquo;, &lsquo;<samp>&quot;</samp>&rsquo;, &lsquo;<samp>\</samp>&rsquo;, or newline.  A
backslash-newline pair is treated as a line continuation (that is, it is
removed from the input stream and effectively ignored<a name="DOCF7" href="#FOOT7"><sup>7</sup></a>).  A double quote may be quoted within
double quotes by preceding it with a backslash.
</p>
<a name="Variable-expansion"></a>
<h3 class="heading">Variable expansion</h3>

<p>The &lsquo;<samp>$</samp>&rsquo; character introduces variable expansion.  The variable name to
be expanded may be enclosed in braces, which are optional but serve to
protect the variable to be expanded from characters immediately following it
which could be interpreted as part of the name.
</p>
<p>Normal variable names begin with an alphabetic character, followed by zero
or more alphanumeric characters.  These names refer to entries in the GRUB
environment (see <a href="#Environment">Environment</a>).
</p>
<p>Positional variable names consist of one or more digits.  They represent
parameters passed to function calls, with &lsquo;<samp>$1</samp>&rsquo; representing the first
parameter, and so on.
</p>
<p>The special variable name &lsquo;<samp>?</samp>&rsquo; expands to the exit status of the most
recently executed command.  When positional variable names are active, other
special variable names &lsquo;<samp>@</samp>&rsquo;, &lsquo;<samp>*</samp>&rsquo; and &lsquo;<samp>#</samp>&rsquo; are defined and they
expand to all positional parameters with necessary quoting, positional
parameters without any quoting, and positional parameter count respectively.
</p>
<a name="Comments"></a>
<h3 class="heading">Comments</h3>

<p>A word beginning with &lsquo;<samp>#</samp>&rsquo; causes that word and all remaining characters
on that line to be ignored.
</p>
<a name="Simple-commands"></a>
<h3 class="heading">Simple commands</h3>

<p>A <em>simple command</em> is a sequence of words separated by spaces or tabs
and terminated by a semicolon or a newline.  The first word specifies the
command to be executed.  The remaining words are passed as arguments to the
invoked command.
</p>
<p>The return value of a simple command is its exit status.  If the reserved
word <code>!</code> precedes the command, then the return value is instead the
logical negation of the command&rsquo;s exit status.
</p>
<a name="Compound-commands"></a>
<h3 class="heading">Compound commands</h3>

<p>A <em>compound command</em> is one of the following:
</p>
<dl compact="compact">
<dt>for <var>name</var> in <var>word</var> &hellip;; do <var>list</var>; done</dt>
<dd><p>The list of words following <code>in</code> is expanded, generating a list of
items.  The variable <var>name</var> is set to each element of this list in turn,
and <var>list</var> is executed each time.  The return value is the exit status
of the last command that executes.  If the expansion of the items following
<code>in</code> results in an empty list, no commands are executed, and the return
status is 0.
</p>
</dd>
<dt>if <var>list</var>; then <var>list</var>; [elif <var>list</var>; then <var>list</var>;] &hellip; [else <var>list</var>;] fi</dt>
<dd><p>The <code>if</code> <var>list</var> is executed.  If its exit status is zero, the
<code>then</code> <var>list</var> is executed.  Otherwise, each <code>elif</code> <var>list</var>
is executed in turn, and if its exit status is zero, the corresponding
<code>then</code> <var>list</var> is executed and the command completes.  Otherwise,
the <code>else</code> <var>list</var> is executed, if present.  The exit status is the
exit status of the last command executed, or zero if no condition tested
true.
</p>
</dd>
<dt>while <var>cond</var>; do <var>list</var>; done</dt>
<dt>until <var>cond</var>; do <var>list</var>; done</dt>
<dd><p>The <code>while</code> command continuously executes the <code>do</code> <var>list</var> as
long as the last command in <var>cond</var> returns an exit status of zero.  The
<code>until</code> command is identical to the <code>while</code> command, except that
the test is negated; the <code>do</code> <var>list</var> is executed as long as the
last command in <var>cond</var> returns a non-zero exit status.  The exit status
of the <code>while</code> and <code>until</code> commands is the exit status of the last
<code>do</code> <var>list</var> command executed, or zero if none was executed.
</p>
</dd>
<dt>function <var>name</var> { <var>command</var>; &hellip; }</dt>
<dd><p>This defines a function named <var>name</var>.  The <em>body</em> of the function is
the list of commands within braces, each of which must be terminated with a
semicolon or a newline.  This list of commands will be executed whenever
<var>name</var> is specified as the name of a simple command.  Function
definitions do not affect the exit status in <code>$?</code>.  When executed, the
exit status of a function is the exit status of the last command executed in
the body.
</p>
</dd>
<dt>menuentry <var>title</var> [<samp>--class=class</samp> &hellip;] [<samp>--users=users</samp>] [<samp>--unrestricted</samp>] [<samp>--hotkey=key</samp>] [<samp>--id=id</samp>] { <var>command</var>; &hellip; }</dt>
<dd><p>See <a href="#menuentry">menuentry</a>.
</p></dd>
</dl>

<a name="Built_002din-Commands"></a>
<h3 class="heading">Built-in Commands</h3>

<p>Some built-in commands are also provided by GRUB script to help script
writers perform actions that are otherwise not possible.  For example, these
include commands to jump out of a loop without fully completing it, etc.
</p>
<dl compact="compact">
<dt>break [<code>n</code>]</dt>
<dd><p>Exit from within a <code>for</code>, <code>while</code>, or <code>until</code> loop.  If
<code>n</code> is specified, break <code>n</code> levels.  <code>n</code> must be greater than
or equal to 1.  If <code>n</code> is greater than the number of enclosing loops,
all enclosing loops are exited.  The return value is 0 unless <code>n</code> is
not greater than or equal to 1.
</p>
</dd>
<dt>continue [<code>n</code>]</dt>
<dd><p>Resume the next iteration of the enclosing <code>for</code>, <code>while</code> or
<code>until</code> loop.  If <code>n</code> is specified, resume at the <code>n</code>th
enclosing loop.  <code>n</code> must be greater than or equal to 1.  If <code>n</code>
is greater than the number of enclosing loops, the last enclosing loop (the
<em>top-level</em> loop) is resumed.  The return value is 0 unless <code>n</code> is
not greater than or equal to 1.
</p>
</dd>
<dt>return [<code>n</code>]</dt>
<dd><p>Causes a function to exit with the return value specified by <code>n</code>.  If
<code>n</code> is omitted, the return status is that of the last command executed
in the function body.  If used outside a function the return status is
false.
</p>
</dd>
<dt>setparams [<code>arg</code>] &hellip;</dt>
<dd><p>Replace positional parameters starting with <code>$1</code> with arguments to
<code>setparams</code>.
</p>
</dd>
<dt>shift [<code>n</code>]</dt>
<dd><p>The positional parameters from <code>n</code>+1 &hellip; are renamed to
<code>$1</code>&hellip;.  Parameters represented by the numbers <code>$#</code> down to
<code>$#</code>-<code>n</code>+1 are unset.  <code>n</code> must be a non-negative number less
than or equal to <code>$#</code>.  If <code>n</code> is 0, no parameters are changed.
If <code>n</code> is not given, it is assumed to be 1.  If <code>n</code> is greater
than <code>$#</code>, the positional parameters are not changed.  The return
status is greater than zero if <code>n</code> is greater than <code>$#</code> or less
than zero; otherwise 0.
</p>
</dd>
</dl>

<hr>
<a name="Multi_002dboot-manual-config"></a>
<div class="header">
<p>
Next: <a href="#Embedded-configuration" accesskey="n" rel="next">Embedded configuration</a>, Previous: <a href="#Shell_002dlike-scripting" accesskey="p" rel="prev">Shell-like scripting</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Configuration</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Multi_002dboot-manual-config-1"></a>
<h3 class="section">6.4 Multi-boot manual config</h3>

<p>Currently autogenerating config files for multi-boot environments depends on
os-prober and has several shortcomings. While fixing it is scheduled for the
next release, meanwhile you can make use of the power of GRUB syntax and do it
yourself. A possible configuration is detailed here, feel free to adjust to your
needs.
</p>
<p>First create a separate GRUB partition, big enough to hold GRUB. Some of the
following entries show how to load OS installer images from this same partition,
for that you obviously need to make the partition large enough to hold those
images as well.
Mount this partition on/mnt/boot and disable GRUB in all OSes and manually
install self-compiled latest GRUB with:
</p>
<p><code>grub2-install --boot-directory=/mnt/boot /dev/sda</code>
</p>
<p>In all the OSes install GRUB tools but disable installing GRUB in bootsector,
so you&rsquo;ll have menu.lst and grub.cfg available for use. Also disable os-prober
use by setting:
</p>
<p><code>GRUB_DISABLE_OS_PROBER=true</code>
</p>
<p>in /etc/default/grub
</p>
<p>Then write a grub.cfg (/mnt/boot/grub2/grub.cfg):
</p>
<div class="example">
<pre class="example">

menuentry &quot;OS using grub2&quot; {
   insmod xfs
   search --set=root --label OS1 --hint hd0,msdos8
   configfile /boot/grub2/grub.cfg
}

menuentry &quot;OS using grub2-legacy&quot; {
   insmod ext2
   search --set=root --label OS2 --hint hd0,msdos6
   legacy_configfile /boot/grub2/menu.lst
}

menuentry &quot;Windows XP&quot; {
   insmod ntfs
   search --set=root --label WINDOWS_XP --hint hd0,msdos1
   ntldr /ntldr
}

menuentry &quot;Windows 7&quot; {
   insmod ntfs
   search --set=root --label WINDOWS_7 --hint hd0,msdos2
   ntldr /bootmgr
}

menuentry &quot;FreeBSD&quot; {
          insmod zfs
          search --set=root --label freepool --hint hd0,msdos7
          kfreebsd /freebsd@/boot/kernel/kernel
          kfreebsd_module_elf /freebsd@/boot/kernel/opensolaris.ko
          kfreebsd_module_elf /freebsd@/boot/kernel/zfs.ko
          kfreebsd_module /freebsd@/boot/zfs/zpool.cache type=/boot/zfs/zpool.cache
          set kFreeBSD.vfs.root.mountfrom=zfs:freepool/freebsd
          set kFreeBSD.hw.psm.synaptics_support=1
}

menuentry &quot;experimental GRUB&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          multiboot /experimental/grub/i386-pc/core.img
}

menuentry &quot;Fedora 16 installer&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          linux /fedora/vmlinuz lang=en_US keymap=sg resolution=1280x800
          initrd /fedora/initrd.img
}

menuentry &quot;Fedora rawhide installer&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          linux /fedora/vmlinuz repo=ftp://mirror.switch.ch/mirror/fedora/linux/development/rawhide/x86_64 lang=en_US keymap=sg resolution=1280x800
          initrd /fedora/initrd.img
}

menuentry &quot;Debian sid installer&quot; {
          search --set=root --label GRUB --hint hd0,msdos5
          linux /debian/dists/sid/main/installer-amd64/current/images/hd-media/vmlinuz
          initrd /debian/dists/sid/main/installer-amd64/current/images/hd-media/initrd.gz
}

</pre></div>

<p>Notes:
</p><ul>
<li> Argument to search after &ndash;label is FS LABEL. You can also use UUIDs with &ndash;fs-uuid UUID instead of &ndash;label LABEL. You could also use direct <code>root=hd0,msdosX</code> but this is not recommended due to device name instability.
</li></ul>

<hr>
<a name="Embedded-configuration"></a>
<div class="header">
<p>
Previous: <a href="#Multi_002dboot-manual-config" accesskey="p" rel="prev">Multi-boot manual config</a>, Up: <a href="#Configuration" accesskey="u" rel="up">Configuration</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Embedding-a-configuration-file-into-GRUB"></a>
<h3 class="section">6.5 Embedding a configuration file into GRUB</h3>

<p>GRUB supports embedding a configuration file directly into the core image,
so that it is loaded before entering normal mode.  This is useful, for
example, when it is not straightforward to find the real configuration file,
or when you need to debug problems with loading that file.
<code>grub2-install</code> uses this feature when it is not using BIOS disk
functions or when installing to a different disk from the one containing
<samp>/boot/grub</samp>, in which case it needs to use the <code>search</code>
command (see <a href="#search">search</a>) to find <samp>/boot/grub</samp>.
</p>
<p>To embed a configuration file, use the <samp>-c</samp> option to
<code>grub2-mkimage</code>.  The file is copied into the core image, so it may
reside anywhere on the file system, and may be removed after running
<code>grub2-mkimage</code>.
</p>
<p>After the embedded configuration file (if any) is executed, GRUB will load
the &lsquo;<samp>normal</samp>&rsquo; module (see <a href="#normal">normal</a>), which will then read the real
configuration file from <samp>$prefix/grub.cfg</samp>.  By this point, the
<code>root</code> variable will also have been set to the root device name.  For
example, <code>prefix</code> might be set to &lsquo;<samp>(hd0,1)/boot/grub</samp>&rsquo;, and
<code>root</code> might be set to &lsquo;<samp>hd0,1</samp>&rsquo;.  Thus, in most cases, the embedded
configuration file only needs to set the <code>prefix</code> and <code>root</code>
variables, and then drop through to GRUB&rsquo;s normal processing.  A typical
example of this might look like this:
</p>
<div class="example">
<pre class="example">search.fs_uuid 01234567-89ab-cdef-0123-456789abcdef root
set prefix=($root)/boot/grub
</pre></div>

<p>(The &lsquo;<samp>search_fs_uuid</samp>&rsquo; module must be included in the core image for this
example to work.)
</p>
<p>In more complex cases, it may be useful to read other configuration files
directly from the embedded configuration file.  This allows such things as
reading files not called <samp>grub.cfg</samp>, or reading files from a directory
other than that where GRUB&rsquo;s loadable modules are installed.  To do this,
include the &lsquo;<samp>configfile</samp>&rsquo; and &lsquo;<samp>normal</samp>&rsquo; modules in the core image,
and embed a configuration file that uses the <code>configfile</code> command to
load another file.  The following example of this also requires the
<code>echo</code>, <code>search_label</code>, and <code>test</code> modules to be
included in the core image:
</p>
<div class="example">
<pre class="example">search.fs_label grub root
if [ -e /boot/grub2/example/test1.cfg ]; then
    set prefix=($root)/boot/grub
    configfile /boot/grub2/example/test1.cfg
else
    if [ -e /boot/grub2/example/test2.cfg ]; then
        set prefix=($root)/boot/grub
        configfile /boot/grub2/example/test2.cfg
    else
        echo &quot;Could not find an example configuration file!&quot;
    fi
fi
</pre></div>

<p>The embedded configuration file may not contain menu entries directly, but
may only read them from elsewhere using <code>configfile</code>.
</p>
<hr>
<a name="Theme-file-format"></a>
<div class="header">
<p>
Next: <a href="#Network" accesskey="n" rel="next">Network</a>, Previous: <a href="#Configuration" accesskey="p" rel="prev">Configuration</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Theme-file-format-1"></a>
<h2 class="chapter">7 Theme file format</h2>
<a name="Introduction-1"></a>
<h3 class="section">7.1 Introduction</h3>
<p>The GRUB graphical menu supports themes that can customize the layout and
appearance of the GRUB boot menu.  The theme is configured through a plain
text file that specifies the layout of the various GUI components (including
the boot menu, timeout progress bar, and text messages) as well as the
appearance using colors, fonts, and images. Example is available in docs/example_theme.txt
</p>
<a name="Theme-Elements"></a>
<h3 class="section">7.2 Theme Elements</h3>
<a name="Colors"></a>
<h4 class="subsection">7.2.1 Colors</h4>

<p>Colors can be specified in several ways:
</p>
<ul>
<li> HTML-style &ldquo;#RRGGBB&rdquo; or &ldquo;#RGB&rdquo; format, where *R*, *G*, and *B* are hexadecimal digits (e.g., &ldquo;#8899FF&rdquo;)
</li><li> as comma-separated decimal RGB values (e.g., &ldquo;128, 128, 255&rdquo;)
</li><li> with &ldquo;SVG 1.0 color names&rdquo; (e.g., &ldquo;cornflowerblue&rdquo;) which must be specified in lowercase.
</li></ul>
<a name="Fonts"></a>
<h4 class="subsection">7.2.2 Fonts</h4>
<p>The fonts GRUB uses &ldquo;PFF2 font format&rdquo; bitmap fonts.  Fonts are specified
with full font names.  Currently there is no
provision for a preference list of fonts, or deriving one font from another.
Fonts are loaded with the &ldquo;loadfont&rdquo; command in GRUB (<a href="#loadfont">loadfont</a>).  To see the list of
loaded fonts, execute the &ldquo;lsfonts&rdquo; command (<a href="#lsfonts">lsfonts</a>).  If there are too many fonts to
fit on screen, do &ldquo;set pager=1&rdquo; before executing &ldquo;lsfonts&rdquo;.
</p>

<a name="Progress-Bar"></a>
<h4 class="subsection">7.2.3 Progress Bar</h4>

<div class="float"><a name="Pixmap_002dstyled-progress-bar"></a>
<div class="float-caption"><p><strong>Figure 7.1
</strong></p></div></div>
<div class="float"><a name="Plain-progress-bar_002c-drawn-with-solid-color_002e"></a>
<div class="float-caption"><p><strong>Figure 7.2
</strong></p></div></div>
<p>Progress bars are used to display the remaining time before GRUB boots the
default menu entry.  To create a progress bar that will display the remaining
time before automatic boot, simply create a &ldquo;progress_bar&rdquo; component with
the id &ldquo;__timeout__&rdquo;.  This indicates to GRUB that the progress bar should
be updated as time passes, and it should be made invisible if the countdown to
automatic boot is interrupted by the user.
</p>
<p>Progress bars may optionally have text displayed on them.  This text is
controlled by variable &ldquo;text&rdquo; which contains a printf template with the
only argument %d is the number of seconds remaining. Additionally special
values &ldquo;@TIMEOUT_NOTIFICATION_SHORT@&rdquo;, &ldquo;@TIMEOUT_NOTIFICATION_MIDDLE@&rdquo;,
&ldquo;@TIMEOUT_NOTIFICATION_LONG@&rdquo; are replaced with standard and translated
templates.
</p>
<a name="Circular-Progress-Indicator"></a>
<h4 class="subsection">7.2.4 Circular Progress Indicator</h4>

<p>The circular progress indicator functions similarly to the progress bar.  When
given an id of &ldquo;__timeout__&rdquo;, GRUB updates the circular progress indicator&rsquo;s
value to indicate the time remaining.  For the circular progress indicator,
there are two images used to render it:  the *center* image, and the *tick*
image.  The center image is rendered in the center of the component, while the
tick image is used to render each mark along the circumference of the
indicator.
</p>

<a name="Labels"></a>
<h4 class="subsection">7.2.5 Labels</h4>

<p>Text labels can be placed on the boot screen.  The font, color, and horizontal
alignment can be specified for labels.  If a label is given the id
&ldquo;__timeout__&rdquo;, then the &ldquo;text&rdquo; property for that label is also updated
with a message informing the user of the number of seconds remaining until
automatic boot.  This is useful in case you want the text displayed somewhere
else instead of directly on the progress bar.
</p>

<p>The boot menu where GRUB displays the menu entries from the &ldquo;grub.cfg&rdquo; file.
It is a list of items, where each item has a title and an optional icon.  The
icon is selected based on the *classes* specified for the menu entry.  If
there is a PNG file named &ldquo;myclass.png&rdquo; in the &ldquo;grub/themes/icons&rdquo;
directory, it will be displayed for items which have the class *myclass*.  The
boot menu can be customized in several ways, such as the font and color used
for the menu entry title, and by specifying styled boxes for the menu itself
and for the selected item highlight.
</p>

<a name="Styled-Boxes"></a>
<h4 class="subsection">7.2.7 Styled Boxes</h4>

<p>One of the most important features for customizing the layout is the use of
 *styled boxes*.  A styled box is composed of 9 rectangular (and potentially
empty) regions, which are used to seamlessly draw the styled box on screen:
</p>
<table>
<tr><td width="30%">Northwest (nw)</td><td width="30%">North (n)</td><td width="30%">Northeast (ne)</td></tr>
<tr><td width="30%">West (w)</td><td width="30%">Center (c)</td><td width="30%">East (e)</td></tr>
<tr><td width="30%">Southwest (sw)</td><td width="30%">South (s)</td><td width="30%">Southeast (se)</td></tr>
</table>

<p>To support any size of box on screen, the center slice and the slices for the
top, bottom, and sides are all scaled to the correct size for the component on
screen, using the following rules:
</p>
<ol>
<li> The edge slices (north, south, east, and west) are scaled in the direction of the edge they are adjacent to.  For instance, the west slice is scaled vertically.
</li><li> The corner slices (northwest, northeast, southeast, and southwest) are not scaled.
</li><li> The center slice is scaled to fill the remaining space in the middle.
</li></ol>

<p>As an example of how an image might be sliced up, consider the styled box
used for a terminal view.
</p>
<div class="float"><a name="An-example-of-the-slices-_0028in-red_0029-used-for-a-terminal-window_002e-This-drawing-was-created-and-sliced-in-Inkscape_005f_002c-as-the-next-section-explains_002e"></a>
<div class="float-caption"><p><strong>Figure 7.3
</strong></p></div></div>   
<a name="Creating-Styled-Box-Images"></a>
<h4 class="subsection">7.2.8 Creating Styled Box Images</h4>

<p>The Inkscape_ scalable vector graphics editor is a very useful tool for
creating styled box images.  One process that works well for slicing a drawing
into the necessary image slices is:
</p>
<ol>
<li> Create or open the drawing you&rsquo;d like use.
</li><li> Create a new layer on the top of the layer stack.  Make it visible.  Select this layer as the current layer.
</li><li> Draw 9 rectangles on your drawing where you&rsquo;d like the slices to be.  Clear the fill option, and set the stroke to 1 pixel wide solid stroke.  The corners of the slices must meet precisely; if it is off by a single pixel, it will probably be evident when the styled box is rendered in the GRUB menu.  You should probably go to File | Document Properties | Grids and enable a grid or create a guide (click on one of the rulers next to the drawing and drag over the drawing; release the mouse button to place the guide) to help place the rectangles precisely.
</li><li> Right click on the center slice rectangle and choose Object Properties. Change the &quot;Id&quot; to &ldquo;slice_c&ldquo; and click Set.  Repeat this for the remaining 8 rectangles, giving them Id values of &ldquo;slice_n&ldquo;, &ldquo;slice_ne&ldquo;, &ldquo;slice_e&ldquo;, and so on according to the location.
</li><li> Save the drawing.
</li><li> Select all the slice rectangles.  With the slice layer selected, you can simply press Ctrl+A to select all rectangles.  The status bar should indicate that 9 rectangles are selected.
</li><li> Click the layer hide icon for the slice layer in the layer palette.  The rectangles will remain selected, even though they are hidden.
</li><li> Choose File | Export Bitmap and check the *Batch export 9 selected objects* box.  Make sure that *Hide all except selected* is unchecked. click *Export*.  This will create PNG files in the same directory as the drawing, named after the slices.  These can now be used for a styled box in a GRUB theme.
</li></ol>

<a name="Theme-File-Manual"></a>
<h3 class="section">7.3 Theme File Manual</h3>

<p>The theme file is a plain text file.  Lines that begin with &ldquo;#&ldquo; are ignored
and considered comments.  (Note: This may not be the case if the previous line
ended where a value was expected.)
</p>
<p>The theme file contains two types of statements:
</p><ol>
<li> Global properties.
</li><li> Component construction.
</li></ol>

<a name="Global-Properties"></a>
<h4 class="subsection">7.3.1 Global Properties</h4>

<a name="Format"></a>
<h4 class="subsection">7.3.2 Format</h4>

<p>Global properties are specified with the simple format:
</p><ul>
<li> name1: value1
</li><li> name2: &quot;value which may contain spaces&quot;
</li><li> name3: #88F
</li></ul>

<p>In this example, name3 is assigned a color value.
</p>

<a name="Global-Property-List"></a>
<h4 class="subsection">7.3.3 Global Property List</h4>

<table>
<tr><td width="30%">title-text</td><td width="60%">Specifies the text to display at the top center of the screen as a title.</td></tr>
<tr><td width="30%">title-font</td><td width="60%">Defines the font used for the title message at the top of the screen.</td></tr>
<tr><td width="30%">title-color</td><td width="60%">Defines the color of the title message.</td></tr>
<tr><td width="30%">message-font</td><td width="60%">Currently unused. Left for backward compatibility.</td></tr>
<tr><td width="30%">message-color</td><td width="60%">Currently unused. Left for backward compatibility.</td></tr>
<tr><td width="30%">message-bg-color</td><td width="60%">Currently unused. Left for backward compatibility.</td></tr>
<tr><td width="30%">desktop-image</td><td width="60%">Specifies the image to use as the background.  It will be scaled
   to fit the screen size or proportionally scaled depending on the scale
   method.</td></tr>
<tr><td width="30%">desktop-image-scale-method</td><td width="60%">Specifies the scaling method for the *desktop-image*. Options are
   &ldquo;stretch&ldquo;, &ldquo;crop&ldquo;, &ldquo;padding&ldquo;, &ldquo;fitwidth&ldquo;, &ldquo;fitheight&ldquo;.
   &ldquo;stretch&ldquo; for fitting the screen size. Otherwise it is proportional
   scaling of a part of *desktop-image* to the part of the screen.
   &ldquo;crop&ldquo; part of the *desktop-image* will be proportionally scaled to
   fit the screen sizes. &ldquo;padding&ldquo; the entire *desktop-image* will be
   contained on the screen. &ldquo;fitwidth&ldquo; for fitting the *desktop-image*&rsquo;s
   width with screen width. &ldquo;fitheight&ldquo; for fitting the *desktop-image*&rsquo;s
   height with the screen height. Default is &ldquo;stretch&ldquo;.</td></tr>
<tr><td width="30%">desktop-image-h-align</td><td width="60%">Specifies the horizontal alignment of the *desktop-image* if
   *desktop-image-scale-method* isn&rsquo;t equeal to &ldquo;stretch&ldquo;. Options are
   &ldquo;left&ldquo;, &ldquo;center&ldquo;, &ldquo;right&ldquo;. Default is &ldquo;center&ldquo;.</td></tr>
<tr><td width="30%">desktop-image-v-align</td><td width="60%">Specifies the vertical alignment of the *desktop-image* if
   *desktop-image-scale-method* isn&rsquo;t equeal to &ldquo;stretch&ldquo;. Options are
   &ldquo;top&ldquo;, &ldquo;center&ldquo;, &ldquo;bottom&ldquo;. Default is &ldquo;center&ldquo;.</td></tr>
<tr><td width="30%">desktop-color</td><td width="60%">Specifies the color for the background if *desktop-image* is not
   specified.</td></tr>
<tr><td width="30%">terminal-box</td><td width="60%">Specifies the file name pattern for the styled box slices used for the
   command line terminal window.  For example, &ldquo;terminal-box: terminal_*.png&ldquo;
   will use the images &ldquo;terminal_c.png&ldquo; as the center area, &ldquo;terminal_n.png&ldquo;
   as the north (top) edge, &ldquo;terminal_nw.png&ldquo; as the northwest (upper left)
   corner, and so on.  If the image for any slice is not found, it will simply
   be left empty.</td></tr>
<tr><td width="30%">terminal-border</td><td width="60%">Specifies the border width of the terminal window.</td></tr>
<tr><td width="30%">terminal-left</td><td width="60%">Specifies the left coordinate of the terminal window.</td></tr>
<tr><td width="30%">terminal-top</td><td width="60%">Specifies the top coordinate of the terminal window.</td></tr>
<tr><td width="30%">terminal-width</td><td width="60%">Specifies the width of the terminal window.</td></tr>
<tr><td width="30%">terminal-height</td><td width="60%">Specifies the height of the terminal window.</td></tr>
</table>

<a name="Component-Construction"></a>
<h4 class="subsection">7.3.4 Component Construction</h4>

<p>Greater customizability comes is provided by components.  A tree of components
forms the user interface.  *Containers* are components that can contain other
components, and there is always a single root component which is an instance
of a *canvas* container.
</p>
<p>Components are created in the theme file by prefixing the type of component
with a &rsquo;+&rsquo; sign:
</p>
<p><code>   + label { text=&quot;GRUB&quot; font=&quot;aqui 11&quot; color=&quot;#8FF&quot; } </code>
</p>
<p>properties of a component are specified as &quot;name = value&quot; (whitespace
surrounding tokens is optional and is ignored) where *value* may be:
</p><ul>
<li> a single word (e.g., &ldquo;align = center&ldquo;, &ldquo;color = #FF8080&ldquo;),
</li><li> a quoted string (e.g., &ldquo;text = &quot;Hello, World!&quot;&ldquo;), or
</li><li> a tuple (e.g., &ldquo;preferred_size = (120, 80)&ldquo;).
</li></ul>

<a name="Component-List"></a>
<h4 class="subsection">7.3.5 Component List</h4>

<p>The following is a list of the components and the properties they support.
</p>
<ul>
<li> label
   A label displays a line of text.
   
<p>Properties:
   </p><table>
<tr><td width="20%">id</td><td width="70%">Set to &ldquo;__timeout__&ldquo; to display the time elapsed to an automatical
      boot of the default entry.</td></tr>
<tr><td width="20%">text</td><td width="70%">The text to display. If &ldquo;id&ldquo; is set to &ldquo;__timeout__&ldquo; and no
      &ldquo;text&ldquo; property is set then the amount of seconds will be shown.
      If set to &ldquo;@KEYMAP_SHORT@&ldquo;, &ldquo;@KEYMAP_MIDDLE@&ldquo; or
      &ldquo;@KEYMAP_LONG@&ldquo; then predefined hotkey information will be shown.</td></tr>
<tr><td width="20%">font</td><td width="70%">The font to use for text display.</td></tr>
<tr><td width="20%">color</td><td width="70%">The color of the text.</td></tr>
<tr><td width="20%">align</td><td width="70%">The horizontal alignment of the text within the component.
      Options are &ldquo;left&ldquo;, &ldquo;center&ldquo; and &ldquo;right&ldquo;.</td></tr>
<tr><td width="20%">visible</td><td width="70%">Set to &ldquo;false&ldquo; to hide the label.</td></tr>
</table>

</li><li> image
   A component that displays an image.  The image is scaled to fit
   the component.

<p>Properties:
</p>
<table>
<tr><td width="20%">file</td><td width="70%">The full path to the image file to load.</td></tr>
</table>

</li><li> progress_bar
   Displays a horizontally oriented progress bar.  It can be rendered using
   simple solid filled rectangles, or using a pair of pixmap styled boxes.

<p>Properties:
</p>
<table>
<tr><td width="20%">id</td><td width="70%">Set to &ldquo;__timeout__&ldquo; to display the time elapsed to an automatical
      boot of the default entry.</td></tr>
<tr><td width="20%">fg_color</td><td width="70%">The foreground color for plain solid color rendering.</td></tr>
<tr><td width="20%">bg_color</td><td width="70%">The background color for plain solid color rendering.</td></tr>
<tr><td width="20%">border_color</td><td width="70%">The border color for plain solid color rendering.</td></tr>
<tr><td width="20%">text_color</td><td width="70%">The text color.</td></tr>
<tr><td width="20%">bar_style</td><td width="70%">The styled box specification for the frame of the progress bar.
      Example: &ldquo;progress_frame_*.png&ldquo;
      If the value is equal to &ldquo;highlight_style&ldquo; then no styled boxes
      will be shown.</td></tr>
<tr><td width="20%">highlight_style</td><td width="70%">The styled box specification for the highlighted region of the
      progress bar. This box will be used to paint just the highlighted region
      of the bar, and will be increased in size as the bar nears completion.
      Example: &ldquo;progress_hl_*.png&ldquo;.
      If the value is equal to &ldquo;bar_style&ldquo; then no styled boxes
      will be shown.</td></tr>
<tr><td width="20%">highlight_overlay</td><td width="70%">If this option is set to &ldquo;true&ldquo; then the highlight box
      side slices (every slice except the center slice) will overlay the
      frame box side slices. And the center slice of the highlight box
      can move all the way (from top to bottom), being drawn on the center
      slice of the frame box. That way we can make a progress bar with
      round-shaped edges so there won&rsquo;t be a free space from the highlight to
      the frame in top and bottom scrollbar positions. Default is &ldquo;false&ldquo;.</td></tr>
<tr><td width="20%">font</td><td width="70%">The font to use for progress bar.</td></tr>
<tr><td width="20%">text</td><td width="70%">The text to display on the progress bar.  If the progress bar&rsquo;s ID
      is set to &ldquo;__timeout__&ldquo; and the value of this property is set to
      &ldquo;@TIMEOUT_NOTIFICATION_SHORT@&ldquo;, &ldquo;@TIMEOUT_NOTIFICATION_MIDDLE@&ldquo;
      or &ldquo;@TIMEOUT_NOTIFICATION_LONG@&ldquo;, then GRUB will update this
      property with an informative message as the timeout approaches.</td></tr>
</table>

</li><li> circular_progress
   Displays a circular progress indicator.  The appearance of this component
   is determined by two images:  the *center* image and the *tick* image.  The
   center image is generally larger and will be drawn in the center of the
   component.  Around the circumference of a circle within the component, the
   tick image will be drawn a certain number of times, depending on the
   properties of the component.

<p>Properties:
</p>
<table>
<tr><td width="30%">id</td><td width="60%">Set to &ldquo;__timeout__&ldquo; to display the time elapsed to an automatical
      boot of the default entry.</td></tr>
<tr><td width="30%">center_bitmap</td><td width="60%">The file name of the image to draw in the center of the component.</td></tr>
<tr><td width="30%">tick_bitmap</td><td width="60%">The file name of the image to draw for the tick marks.</td></tr>
<tr><td width="30%">num_ticks</td><td width="60%">The number of ticks that make up a full circle.</td></tr>
<tr><td width="30%">ticks_disappear</td><td width="60%">Boolean value indicating whether tick marks should progressively appear,
      or progressively disappear as *value* approaches *end*.  Specify
      &ldquo;true&ldquo; or &ldquo;false&ldquo;. Default is &ldquo;false&ldquo;.</td></tr>
<tr><td width="30%">start_angle</td><td width="60%">The position of the first tick mark to appear or disappear.
      Measured in &quot;parrots&quot;, 1 &quot;parrot&quot; = 1 / 256 of the full circle.
      Use values &ldquo;xxx deg&ldquo; or &ldquo;xxx \xc2\xb0&ldquo; to set the angle in degrees.</td></tr>
</table>

</li><li> boot_menu
   Displays the GRUB boot menu.  It allows selecting items and executing them.

<p>Properties:
</p>
<table>
<tr><td width="40%">item_font</td><td width="50%">The font to use for the menu item titles.</td></tr>
<tr><td width="40%">selected_item_font</td><td width="50%">The font to use for the selected menu item, or &ldquo;inherit&ldquo; (the default)
      to use &ldquo;item_font&ldquo; for the selected menu item as well.</td></tr>
<tr><td width="40%">item_color</td><td width="50%">The color to use for the menu item titles.</td></tr>
<tr><td width="40%">selected_item_color</td><td width="50%">The color to use for the selected menu item, or &ldquo;inherit&ldquo; (the default)
      to use &ldquo;item_color&ldquo; for the selected menu item as well.</td></tr>
<tr><td width="40%">icon_width</td><td width="50%">The width of menu item icons.  Icons are scaled to the specified size.</td></tr>
<tr><td width="40%">icon_height</td><td width="50%">The height of menu item icons.</td></tr>
<tr><td width="40%">item_height</td><td width="50%">The height of each menu item in pixels.</td></tr>
<tr><td width="40%">item_padding</td><td width="50%">The amount of space in pixels to leave on each side of the menu item
      contents.</td></tr>
<tr><td width="40%">item_icon_space</td><td width="50%">The space between an item&rsquo;s icon and the title text, in pixels.</td></tr>
<tr><td width="40%">item_spacing</td><td width="50%">The amount of space to leave between menu items, in pixels.</td></tr>
<tr><td width="40%">menu_pixmap_style</td><td width="50%">The image file pattern for the menu frame styled box.
      Example:  &ldquo;menu_*.png&ldquo; (this will use images such as &ldquo;menu_c.png&ldquo;,
      &ldquo;menu_w.png&ldquo;, &lsquo;menu_nw.png&ldquo;, etc.)</td></tr>
<tr><td width="40%">item_pixmap_style</td><td width="50%">The image file pattern for the item styled box.</td></tr>
<tr><td width="40%">selected_item_pixmap_style</td><td width="50%">The image file pattern for the selected item highlight styled box.</td></tr>
<tr><td width="40%">scrollbar</td><td width="50%">Boolean value indicating whether the scroll bar should be drawn if the
      frame and thumb styled boxes are configured.</td></tr>
<tr><td width="40%">scrollbar_frame</td><td width="50%">The image file pattern for the entire scroll bar.
      Example:  &ldquo;scrollbar_*.png&ldquo;</td></tr>
<tr><td width="40%">scrollbar_thumb</td><td width="50%">The image file pattern for the scroll bar thumb (the part of the scroll
      bar that moves as scrolling occurs).
      Example:  &ldquo;scrollbar_thumb_*.png&ldquo;</td></tr>
<tr><td width="40%">scrollbar_thumb_overlay</td><td width="50%">If this option is set to &ldquo;true&ldquo; then the scrollbar thumb
      side slices (every slice except the center slice) will overlay the
      scrollbar frame side slices. And the center slice of the scrollbar_thumb
      can move all the way (from top to bottom), being drawn on the center
      slice of the scrollbar frame. That way we can make a scrollbar with
      round-shaped edges so there won&rsquo;t be a free space from the thumb to
      the frame in top and bottom scrollbar positions. Default is &ldquo;false&ldquo;.</td></tr>
<tr><td width="40%">scrollbar_slice</td><td width="50%">The menu frame styled box&rsquo;s slice in which the scrollbar will be
      drawn. Possible values are &ldquo;west&ldquo;, &ldquo;center&ldquo;, &ldquo;east&ldquo; (default).
      &ldquo;west&ldquo; - the scrollbar will be drawn in the west slice (right-aligned).
      &ldquo;east&ldquo; - the scrollbar will be drawn in the east slice (left-aligned).
      &ldquo;center&ldquo; - the scrollbar will be drawn in the center slice.
      Note: in case of &ldquo;center&ldquo; slice:
      a) If the scrollbar should be drawn then boot menu entry&rsquo;s width is
      decreased by the scrollbar&rsquo;s width and the scrollbar is drawn at the
      right side of the center slice.
      b) If the scrollbar won&rsquo;t be drawn then the boot menu entry&rsquo;s width
      is the width of the center slice.
      c) We don&rsquo;t necessary need the menu pixmap box to display the scrollbar.</td></tr>
<tr><td width="40%">scrollbar_left_pad</td><td width="50%">The left scrollbar padding in pixels.
      Unused if &ldquo;scrollbar_slice&ldquo; is &ldquo;west&ldquo;.</td></tr>
<tr><td width="40%">scrollbar_right_pad</td><td width="50%">The right scrollbar padding in pixels.
      Unused if &ldquo;scrollbar_slice&ldquo; is &ldquo;east&ldquo;.</td></tr>
<tr><td width="40%">scrollbar_top_pad</td><td width="50%">The top scrollbar padding in pixels.</td></tr>
<tr><td width="40%">scrollbar_bottom_pad</td><td width="50%">The bottom scrollbar padding in pixels.</td></tr>
<tr><td width="40%">visible</td><td width="50%">Set to &ldquo;false&ldquo; to hide the boot menu.</td></tr>
</table>

</li><li> canvas
   Canvas is a container that allows manual placement of components within it.
   It does not alter the positions of its child components.  It assigns all
   child components their preferred sizes.

</li><li> hbox
   The *hbox* container lays out its children from left to right, giving each
   one its preferred width.  The height of each child is set to the maximum of
   the preferred heights of all children.
   
</li><li> vbox
   The *vbox* container lays out its children from top to bottom, giving each
   one its preferred height.  The width of each child is set to the maximum of
   the preferred widths of all children.
</li></ul>

<a name="Common-properties"></a>
<h4 class="subsection">7.3.6 Common properties</h4>

<p>The following properties are supported by all components:
</p><dl compact="compact">
<dt>&lsquo;<samp>left</samp>&rsquo;</dt>
<dd><p>The distance from the left border of container to left border of the object in either of three formats:
        </p><table>
<tr><td width="20%">x</td><td width="70%">Value in pixels</td></tr>
<tr><td width="20%">p%</td><td width="70%">Percentage</td></tr>
<tr><td width="20%">p%+x</td><td width="70%">mixture of both</td></tr>
</table>
</dd>
<dt>&lsquo;<samp>top</samp>&rsquo;</dt>
<dd><p>The distance from the left border of container to left border of the object in same format.
</p></dd>
<dt>&lsquo;<samp>width</samp>&rsquo;</dt>
<dd><p>The width of object in same format.
</p></dd>
<dt>&lsquo;<samp>height</samp>&rsquo;</dt>
<dd><p>The height of object in same format.
</p></dd>
<dt>&lsquo;<samp>id</samp>&rsquo;</dt>
<dd><p>The identifier for the component.  This can be any arbitrary string.
   The ID can be used by scripts to refer to various components in the GUI
   component tree.  Currently, there is one special ID value that GRUB
   recognizes:
</p>
<table>
<tr><td width="20%">&ldquo;__timeout__&ldquo;</td><td width="70%">Component with this ID will be updated by GRUB and will indicate
      time elapsed to an automatical boot of the default entry.
      Affected components: &ldquo;label&ldquo;, &ldquo;circular_progress&ldquo;, &ldquo;progress_bar&ldquo;.</td></tr>
</table>
</dd>
</dl>

<hr>
<a name="Network"></a>
<div class="header">
<p>
Next: <a href="#Serial-terminal" accesskey="n" rel="next">Serial terminal</a>, Previous: <a href="#Theme-file-format" accesskey="p" rel="prev">Theme file format</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Booting-GRUB-from-the-network"></a>
<h2 class="chapter">8 Booting GRUB from the network</h2>

<p>The following instructions don&rsquo;t work for *-emu, i386-qemu, i386-coreboot,
i386-multiboot, mips_loongson, mips-arc and mips_qemu_mips
</p>
<p>To generate a netbootable directory, run:
</p>
<div class="example">
<pre class="example">grub-mknetdir --net-directory=/srv/tftp --subdir=/boot/grub -d /usr/lib/grub/&lt;platform&gt;
</pre></div>

<p>E.g. for i386-pc:
</p>
<div class="example">
<pre class="example">grub-mknetdir --net-directory=/srv/tftp --subdir=/boot/grub -d /usr/lib/grub/i386-pc
</pre></div>

<p>Then follow instructions printed out by grub2-mknetdir on configuring your DHCP
server.
</p>
<p>The grub.cfg file is placed in the same directory as the path output by
grub-mknetdir hereafter referred to as FWPATH. GRUB will search for its 
configuration files in order using the following rules where the appended
value corresponds to a value on the client machine.
</p>
<div class="example">
<pre class="example">&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-&lsquo;<samp>(UUID OF NIC)</samp>&rsquo;
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-&lsquo;<samp>(MAC ADDRESS OF NIC)</samp>&rsquo;
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-&lsquo;<samp>(IPv4 OR IPv6 ADDRESS)</samp>&rsquo;
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg
</pre></div>

<p>The client will only attempt to look up an IPv6 address config once, however,
it will try the IPv4 multiple times. The concrete example below shows what
would happen under the IPv4 case.
</p>
<div class="example">
<pre class="example">UUID: 7726a678-7fc0-4853-a4f6-c85ac36a120a
MAC:  52:54:00:ec:33:81
IPV4: 10.0.0.130 (0A000082)
</pre></div>

<div class="example">
<pre class="example">&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-7726a678-7fc0-4853-a4f6-c85ac36a120a
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-52-54-00-ec-33-81
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0A000082
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0A00008
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0A0000
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0A000
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0A00
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0A0
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0A
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg-0
&lsquo;<samp>(FWPATH)</samp>&rsquo;/grub.cfg
</pre></div>

<p>After GRUB has started, files on the TFTP server will be accessible via the
&lsquo;<samp>(tftp)</samp>&rsquo; device.
</p>
<p>The server IP address can be controlled by changing the
&lsquo;<samp>(tftp)</samp>&rsquo; device name to &lsquo;<samp>(tftp,<var>server-ip</var>)</samp>&rsquo;. Note that
this should be changed both in the prefix and in any references to the
device name in the configuration file.
</p>
<p>GRUB provides several environment variables which may be used to inspect or
change the behaviour of the PXE device. In the following description
<var>&lt;interface&gt;</var> is placeholder for the name of network interface (platform
dependent):
</p>
<dl compact="compact">
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_ip</samp>&rsquo;</dt>
<dd><p>The network interface&rsquo;s IP address.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_mac</samp>&rsquo;</dt>
<dd><p>The network interface&rsquo;s MAC address.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_hostname</samp>&rsquo;</dt>
<dd><p>The client host name provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_domain</samp>&rsquo;</dt>
<dd><p>The client domain name provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_rootpath</samp>&rsquo;</dt>
<dd><p>The path to the client&rsquo;s root disk provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_extensionspath</samp>&rsquo;</dt>
<dd><p>The path to additional DHCP vendor extensions provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_boot_file</samp>&rsquo;</dt>
<dd><p>The boot file name provided by DHCP.  Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_dhcp_server_name</samp>&rsquo;</dt>
<dd><p>The name of the DHCP server responsible for these boot parameters.
Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_<var>&lt;interface&gt;</var>_next_server</samp>&rsquo;</dt>
<dd><p>The IP address of the next (usually, TFTP) server provided by DHCP.
Read-only.
</p>
</dd>
<dt>&lsquo;<samp>net_default_interface</samp>&rsquo;</dt>
<dd><p>Initially set to name of network interface that was used to load grub.
Read-write, although setting it affects only interpretation of
&lsquo;<samp>net_default_ip</samp>&rsquo; and &lsquo;<samp>net_default_mac</samp>&rsquo;
</p>
</dd>
<dt>&lsquo;<samp>net_default_ip</samp>&rsquo;</dt>
<dd><p>The IP address of default interface.  Read-only. This is alias for the
&lsquo;<samp>net_${net_default_interface}_ip</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>net_default_mac</samp>&rsquo;</dt>
<dd><p>The default interface&rsquo;s MAC address.  Read-only.  This is alias for the
&lsquo;<samp>net_${net_default_interface}_mac</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>net_default_server</samp>&rsquo;</dt>
<dd><p>The default server used by network drives (see <a href="#Device-syntax">Device syntax</a>).  Read-write,
although setting this is only useful before opening a network device.
</p>
</dd>
</dl>

<hr>
<a name="Serial-terminal"></a>
<div class="header">
<p>
Next: <a href="#Vendor-power_002don-keys" accesskey="n" rel="next">Vendor power-on keys</a>, Previous: <a href="#Network" accesskey="p" rel="prev">Network</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Using-GRUB-via-a-serial-line"></a>
<h2 class="chapter">9 Using GRUB via a serial line</h2>

<p>This chapter describes how to use the serial terminal support in GRUB.
</p>
<p>If you have many computers or computers with no display/keyboard, it
could be very useful to control the computers through serial
communications. To connect one computer with another via a serial line,
you need to prepare a null-modem (cross) serial cable, and you may need
to have multiport serial boards, if your computer doesn&rsquo;t have extra
serial ports. In addition, a terminal emulator is also required, such as
minicom. Refer to a manual of your operating system, for more
information.
</p>
<p>As for GRUB, the instruction to set up a serial terminal is quite
simple.  Here is an example:
</p>
<div class="example">
<pre class="example">grub&gt; <kbd>serial --unit=0 --speed=9600</kbd>
grub&gt; <kbd>terminal_input serial; terminal_output serial</kbd>
</pre></div>

<p>The command <code>serial</code> initializes the serial unit 0 with the
speed 9600bps. The serial unit 0 is usually called &lsquo;<samp>COM1</samp>&rsquo;, so, if
you want to use COM2, you must specify &lsquo;<samp>--unit=1</samp>&rsquo; instead. This
command accepts many other options, so please refer to <a href="#serial">serial</a>,
for more details.
</p>
<p>The commands <code>terminal_input</code> (see <a href="#terminal_005finput">terminal_input</a>) and
<code>terminal_output</code> (see <a href="#terminal_005foutput">terminal_output</a>) choose which type of
terminal you want to use. In the case above, the terminal will be a
serial terminal, but you can also pass <code>console</code> to the command,
as &lsquo;<samp>terminal_input serial console</samp>&rsquo;. In this case, a terminal in which
you press any key will be selected as a GRUB terminal. In the example above,
note that you need to put both commands on the same command line, as you
will lose the ability to type commands on the console after the first
command.
</p>
<p>However, note that GRUB assumes that your terminal emulator is
compatible with VT100 by default. This is true for most terminal
emulators nowadays, but you should pass the option <samp>--dumb</samp> to
the command if your terminal emulator is not VT100-compatible or
implements few VT100 escape sequences. If you specify this option then
GRUB provides you with an alternative menu interface, because the normal
menu requires several fancy features of your terminal.
</p>

<hr>
<a name="Vendor-power_002don-keys"></a>
<div class="header">
<p>
Next: <a href="#Images" accesskey="n" rel="next">Images</a>, Previous: <a href="#Serial-terminal" accesskey="p" rel="prev">Serial terminal</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Using-GRUB-with-vendor-power_002don-keys"></a>
<h2 class="chapter">10 Using GRUB with vendor power-on keys</h2>

<p>Some laptop vendors provide an additional power-on button which boots
another OS.  GRUB supports such buttons with the &lsquo;<samp>GRUB_TIMEOUT_BUTTON</samp>&rsquo;,
&lsquo;<samp>GRUB_TIMEOUT_STYLE_BUTTON</samp>&rsquo;, &lsquo;<samp>GRUB_DEFAULT_BUTTON</samp>&rsquo;, and
&lsquo;<samp>GRUB_BUTTON_CMOS_ADDRESS</samp>&rsquo; variables in default/grub (see <a href="#Simple-configuration">Simple configuration</a>).  &lsquo;<samp>GRUB_TIMEOUT_BUTTON</samp>&rsquo;,
&lsquo;<samp>GRUB_TIMEOUT_STYLE_BUTTON</samp>&rsquo;, and &lsquo;<samp>GRUB_DEFAULT_BUTTON</samp>&rsquo; are used
instead of the corresponding variables without the &lsquo;<samp>_BUTTON</samp>&rsquo; suffix
when powered on using the special button.  &lsquo;<samp>GRUB_BUTTON_CMOS_ADDRESS</samp>&rsquo;
is vendor-specific and partially model-specific.  Values known to the GRUB
team are:
</p>
<dl compact="compact">
<dt><tt class="key">Dell XPS M1330M</tt></dt>
<dd><p>121:3
</p></dd>
<dt><tt class="key">Dell XPS M1530</tt></dt>
<dd><p>85:3
</p></dd>
<dt><tt class="key">Dell Latitude E4300</tt></dt>
<dd><p>85:3
</p></dd>
<dt><tt class="key">Asus EeePC 1005PE</tt></dt>
<dd><p>84:1 (unconfirmed)
</p></dd>
<dt><tt class="key">LENOVO ThinkPad T410s (2912W1C)</tt></dt>
<dd><p>101:3
</p></dd>
</dl>

<p>To take full advantage of this function, install GRUB into the MBR
(see <a href="#Installing-GRUB-using-grub2_002dinstall">Installing GRUB using grub2-install</a>).
</p>
<p>If you have a laptop which has a similar feature and not in the above list
could you figure your address and contribute?
To discover the address do the following:
</p><ul>
<li> boot normally
</li><li> <div class="example">
<pre class="example">sudo modprobe nvram
sudo cat /dev/nvram | xxd &gt; normal_button.txt
</pre></div>
</li><li> boot using vendor button
</li><li> <div class="example">
<pre class="example">sudo modprobe nvram
sudo cat /dev/nvram | xxd &gt; normal_vendor.txt
</pre></div>
</li></ul>

<p>Then compare these text files and find where a bit was toggled. E.g. in
case of Dell XPS it was:
</p><div class="example">
<pre class="example">byte 0x47: 20 --&gt; 28
</pre></div>
<p>It&rsquo;s a bit number 3 as seen from following table:
</p><table>
<tr><td width="20%">0</td><td width="20%">01</td></tr>
<tr><td width="20%">1</td><td width="20%">02</td></tr>
<tr><td width="20%">2</td><td width="20%">04</td></tr>
<tr><td width="20%">3</td><td width="20%">08</td></tr>
<tr><td width="20%">4</td><td width="20%">10</td></tr>
<tr><td width="20%">5</td><td width="20%">20</td></tr>
<tr><td width="20%">6</td><td width="20%">40</td></tr>
<tr><td width="20%">7</td><td width="20%">80</td></tr>
</table>

<p>0x47 is decimal 71. Linux nvram implementation cuts first 14 bytes of
CMOS. So the real byte address in CMOS is 71+14=85
So complete address is 85:3
</p>
<hr>
<a name="Images"></a>
<div class="header">
<p>
Next: <a href="#Core-image-size-limitation" accesskey="n" rel="next">Core image size limitation</a>, Previous: <a href="#Vendor-power_002don-keys" accesskey="p" rel="prev">Vendor power-on keys</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GRUB-image-files"></a>
<h2 class="chapter">11 GRUB image files</h2>

<p>GRUB consists of several images: a variety of bootstrap images for starting
GRUB in various ways, a kernel image, and a set of modules which are
combined with the kernel image to form a core image.  Here is a short
overview of them.
</p>
<dl compact="compact">
<dt><samp>boot.img</samp></dt>
<dd><p>On PC BIOS systems, this image is the first part of GRUB to start.  It is
written to a master boot record (MBR) or to the boot sector of a partition.
Because a PC boot sector is 512 bytes, the size of this image is exactly 512
bytes.
</p>
<p>The sole function of <samp>boot.img</samp> is to read the first sector of the core
image from a local disk and jump to it.  Because of the size restriction,
<samp>boot.img</samp> cannot understand any file system structure, so
<code>grub2-install</code> hardcodes the location of the first sector of the
core image into <samp>boot.img</samp> when installing GRUB.
</p>
</dd>
<dt><samp>diskboot.img</samp></dt>
<dd><p>This image is used as the first sector of the core image when booting from a
hard disk.  It reads the rest of the core image into memory and starts the
kernel.  Since file system handling is not yet available, it encodes the
location of the core image using a block list format.
</p>
</dd>
<dt><samp>cdboot.img</samp></dt>
<dd><p>This image is used as the first sector of the core image when booting from a
CD-ROM drive.  It performs a similar function to <samp>diskboot.img</samp>.
</p>
</dd>
<dt><samp>pxeboot.img</samp></dt>
<dd><p>This image is used as the start of the core image when booting from the
network using PXE.  See <a href="#Network">Network</a>.
</p>
</dd>
<dt><samp>lnxboot.img</samp></dt>
<dd><p>This image may be placed at the start of the core image in order to make
GRUB look enough like a Linux kernel that it can be booted by LILO using an
&lsquo;<samp>image=</samp>&rsquo; section.
</p>
</dd>
<dt><samp>kernel.img</samp></dt>
<dd><p>This image contains GRUB&rsquo;s basic run-time facilities: frameworks for device
and file handling, environment variables, the rescue mode command-line
parser, and so on.  It is rarely used directly, but is built into all core
images.
</p>
</dd>
<dt><samp>core.img</samp></dt>
<dd><p>This is the core image of GRUB.  It is built dynamically from the kernel
image and an arbitrary list of modules by the <code>grub2-mkimage</code>
program.  Usually, it contains enough modules to access <samp>/boot/grub</samp>,
and loads everything else (including menu handling, the ability to load
target operating systems, and so on) from the file system at run-time.  The
modular design allows the core image to be kept small, since the areas of
disk where it must be installed are often as small as 32KB.
</p>
<p>See <a href="#BIOS-installation">BIOS installation</a>, for details on where the core image can be
installed on PC systems.
</p>
</dd>
<dt><samp>*.mod</samp></dt>
<dd><p>Everything else in GRUB resides in dynamically loadable modules.  These are
often loaded automatically, or built into the core image if they are
essential, but may also be loaded manually using the <code>insmod</code>
command (see <a href="#insmod">insmod</a>).
</p></dd>
</dl>

<a name="For-GRUB-Legacy-users"></a>
<h3 class="heading">For GRUB Legacy users</h3>

<p>GRUB 2 has a different design from GRUB Legacy, and so correspondences with
the images it used cannot be exact.  Nevertheless, GRUB Legacy users often
ask questions in the terms they are familiar with, and so here is a brief
guide to how GRUB 2&rsquo;s images relate to that.
</p>
<dl compact="compact">
<dt><samp>stage1</samp></dt>
<dd><p>Stage 1 from GRUB Legacy was very similar to <samp>boot.img</samp> in GRUB 2, and
they serve the same function.
</p>
</dd>
<dt><samp>*_stage1_5</samp></dt>
<dd><p>In GRUB Legacy, Stage 1.5&rsquo;s function was to include enough filesystem code
to allow the much larger Stage 2 to be read from an ordinary filesystem.  In
this respect, its function was similar to <samp>core.img</samp> in GRUB 2.
However, <samp>core.img</samp> is much more capable than Stage 1.5 was; since it
offers a rescue shell, it is sometimes possible to recover manually in the
event that it is unable to load any other modules, for example if partition
numbers have changed.  <samp>core.img</samp> is built in a more flexible way,
allowing GRUB 2 to support reading modules from advanced disk types such as
LVM and RAID.
</p>
<p>GRUB Legacy could run with only Stage 1 and Stage 2 in some limited
configurations, while GRUB 2 requires <samp>core.img</samp> and cannot work
without it.
</p>
</dd>
<dt><samp>stage2</samp></dt>
<dd><p>GRUB 2 has no single Stage 2 image.  Instead, it loads modules from
<samp>/boot/grub</samp> at run-time.
</p>
</dd>
<dt><samp>stage2_eltorito</samp></dt>
<dd><p>In GRUB 2, images for booting from CD-ROM drives are now constructed using
<samp>cdboot.img</samp> and <samp>core.img</samp>, making sure that the core image
contains the &lsquo;<samp>iso9660</samp>&rsquo; module.  It is usually best to use the
<code>grub2-mkrescue</code> program for this.
</p>
</dd>
<dt><samp>nbgrub</samp></dt>
<dd><p>There is as yet no equivalent for <samp>nbgrub</samp> in GRUB 2; it was used by
Etherboot and some other network boot loaders.
</p>
</dd>
<dt><samp>pxegrub</samp></dt>
<dd><p>In GRUB 2, images for PXE network booting are now constructed using
<samp>pxeboot.img</samp> and <samp>core.img</samp>, making sure that the core image
contains the &lsquo;<samp>pxe</samp>&rsquo; and &lsquo;<samp>pxecmd</samp>&rsquo; modules.  See <a href="#Network">Network</a>.
</p></dd>
</dl>

<hr>
<a name="Core-image-size-limitation"></a>
<div class="header">
<p>
Next: <a href="#Filesystem" accesskey="n" rel="next">Filesystem</a>, Previous: <a href="#Images" accesskey="p" rel="prev">Images</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Core-image-size-limitation-1"></a>
<h2 class="chapter">12 Core image size limitation</h2>

<p>Heavily limited platforms:
</p><ul>
<li> i386-pc (normal and PXE): the core image size (compressed) is limited by 458240 bytes.
 kernel.img (.text + .data + .bss, uncompressed) is limited by 392704 bytes.
 module size (uncompressed) + kernel.img (.text + .data, uncompressed) is limited by the size of contiguous chunk at 1M address.
</li><li> sparc64-ieee1275: kernel.img (.text + .data + .bss) + modules + 256K (stack) + 2M (heap) is limited by space available at 0x4400. On most platforms it&rsquo;s just 3 or 4M since ieee1275 maps only so much.
</li><li> i386-ieee1275: kernel.img  (.text + .data + .bss) + modules is limited by memory available at 0x10000, at most 596K
</li></ul>

<p>Lightly limited platforms:
</p>
<ul>
<li> *-xen: limited only by adress space and RAM size.
</li><li> i386-qemu: kernel.img (.text + .data + .bss) is limited by 392704 bytes.
                 (core.img would be limited by ROM size but it&rsquo;s unlimited on qemu
</li><li> All EFI platforms: limited by contiguous RAM size and possibly firmware bugs
</li><li> Coreboot and multiboot. kernel.img (.text + .data + .bss) is limited by 392704 bytes.
      module size is limited by the size of contiguous chunk at 1M address.
</li><li> mipsel-loongson (ELF), mips(el)-qemu_mips (ELF): if uncompressed:
                kernel.img (.text + .data) + modules is limited by the space from 80200000 forward
                if compressed:
                kernel.img (.text + .data, uncompressed) + modules (uncompressed)
                + (modules + kernel.img (.text + .data)) (compressed)
                + decompressor is limited by the space from 80200000 forward
</li><li> mipsel-loongson (Flash), mips(el)-qemu_mips (Flash): kernel.img (.text + .data) + modules is limited by the space from 80200000 forward
                               core.img (final) is limited by flash size (512K on yeeloong and fulooong)
</li><li> mips-arc: if uncompressed:
                kernel.img (.text + .data) is limited by the space from 8bd00000 forward
                modules + dummy decompressor  is limited by the space from 8bd00000 backward
                if compressed:
                kernel.img (.text + .data, uncompressed) is limited by the space from 8bd00000 forward
                modules (uncompressed) + (modules + kernel.img (.text + .data)) (compressed, aligned to 1M)
                + 1M (decompressor + scratch space) is limited by the space from 8bd00000 backward
</li><li> powerpc-ieee1275: kernel.img (.text + .data + .bss) + modules is limited by space available at 0x200000
</li></ul>

<hr>
<a name="Filesystem"></a>
<div class="header">
<p>
Next: <a href="#Interface" accesskey="n" rel="next">Interface</a>, Previous: <a href="#Core-image-size-limitation" accesskey="p" rel="prev">Core image size limitation</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Filesystem-syntax-and-semantics"></a>
<h2 class="chapter">13 Filesystem syntax and semantics</h2>

<p>GRUB uses a special syntax for specifying disk drives which can be
accessed by BIOS. Because of BIOS limitations, GRUB cannot distinguish
between IDE, ESDI, SCSI, or others. You must know yourself which BIOS
device is equivalent to which OS device. Normally, that will be clear if
you see the files in a device or use the command <code>search</code>
(see <a href="#search">search</a>).
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Device-syntax" accesskey="1">Device syntax</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">How to specify devices
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#File-name-syntax" accesskey="2">File name syntax</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">How to specify files
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Block-list-syntax" accesskey="3">Block list syntax</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">How to specify block lists
</td></tr>
</table>

<hr>
<a name="Device-syntax"></a>
<div class="header">
<p>
Next: <a href="#File-name-syntax" accesskey="n" rel="next">File name syntax</a>, Up: <a href="#Filesystem" accesskey="u" rel="up">Filesystem</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="How-to-specify-devices"></a>
<h3 class="section">13.1 How to specify devices</h3>

<p>The device syntax is like this:
</p>
<div class="example">
<pre class="example"><code>(<var>device</var>[,<var>partmap-name1</var><var>part-num1</var>[,<var>partmap-name2</var><var>part-num2</var>[,...]]])</code>
</pre></div>

<p>&lsquo;<samp>[]</samp>&rsquo; means the parameter is optional. <var>device</var> depends on the disk
driver in use. BIOS and EFI disks use either &lsquo;<samp>fd</samp>&rsquo; or &lsquo;<samp>hd</samp>&rsquo; followed
by a digit, like &lsquo;<samp>fd0</samp>&rsquo;, or &lsquo;<samp>cd</samp>&rsquo;.
AHCI, PATA (ata), crypto, USB use the name of driver followed by a number.
Memdisk and host are limited to one disk and so it&rsquo;s refered just by driver
name.
RAID (md), ofdisk (ieee1275 and nand), LVM (lvm), LDM, virtio (vdsk)
and arcdisk (arc) use intrinsic name of disk prefixed by driver name.
Additionally just &ldquo;nand&rdquo; refers to the disk aliased as &ldquo;nand&rdquo;.
Conflicts are solved by suffixing a number if necessarry.
Commas need to be escaped.
Loopback uses whatever name specified to <code>loopback</code> command.
Hostdisk uses names specified in device.map as long as it&rsquo;s of the form
[fhc]d[0-9]* or hostdisk/&lt;OS DEVICE&gt;.
For crypto and RAID (md) additionally you can use the syntax
&lt;driver name&gt;uuid/&lt;uuid&gt;.  For LVM additionally you can use the syntax
lvmid/&lt;volume-group-uuid&gt;/&lt;volume-uuid&gt;.
</p>
<div class="example">
<pre class="example">(fd0)
(hd0)
(cd)
(ahci0)
(ata0)
(crypto0)
(usb0)
(cryptouuid/123456789abcdef0123456789abcdef0)
(mduuid/123456789abcdef0123456789abcdef0)
(lvm/system-root)
(lvmid/F1ikgD-2RES-306G-il9M-7iwa-4NKW-EbV1NV/eLGuCQ-L4Ka-XUgR-sjtJ-ffch-bajr-fCNfz5)
(md/myraid)
(md/0)
(ieee1275/disk2)
(ieee1275//pci@1f\,0/ide@d/disk@2)
(nand)
(memdisk)
(host)
(myloop)
(hostdisk//dev/sda)
</pre></div>

<p><var>part-num</var> represents the partition number of <var>device</var>, starting
from one. <var>partname</var> is optional but is recommended since disk may have
several top-level partmaps. Specifying third and later component you can access
to subpartitions.
</p>
<p>The syntax &lsquo;<samp>(hd0)</samp>&rsquo; represents using the entire disk (or the
MBR when installing GRUB), while the syntax &lsquo;<samp>(hd0,1)</samp>&rsquo;
represents using the first partition of the disk (or the boot sector
of the partition when installing GRUB).
</p>
<div class="example">
<pre class="example">(hd0,msdos1)
(hd0,msdos1,msdos5)
(hd0,msdos1,bsd3)
(hd0,netbsd1)
(hd0,gpt1)
(hd0,1,3)
</pre></div>

<p>If you enabled the network support, the special drives
<code>(<var>protocol</var>[,<var>server</var>])</code> are also available. Supported protocols
are &lsquo;<samp>http</samp>&rsquo; and &lsquo;<samp>tftp</samp>&rsquo;. If <var>server</var> is omitted, value of
environment variable &lsquo;<samp>net_default_server</samp>&rsquo; is used.
Before using the network drive, you must initialize the network.
See <a href="#Network">Network</a>, for more information.
</p>
<p>If you boot GRUB from a CD-ROM, &lsquo;<samp>(cd)</samp>&rsquo; is available. See <a href="#Making-a-GRUB-bootable-CD_002dROM">Making a GRUB bootable CD-ROM</a>, for details.
</p>

<hr>
<a name="File-name-syntax"></a>
<div class="header">
<p>
Next: <a href="#Block-list-syntax" accesskey="n" rel="next">Block list syntax</a>, Previous: <a href="#Device-syntax" accesskey="p" rel="prev">Device syntax</a>, Up: <a href="#Filesystem" accesskey="u" rel="up">Filesystem</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="How-to-specify-files"></a>
<h3 class="section">13.2 How to specify files</h3>

<p>There are two ways to specify files, by <em>absolute file name</em> and by
<em>block list</em>.
</p>
<p>An absolute file name resembles a Unix absolute file name, using
&lsquo;<samp>/</samp>&rsquo; for the directory separator (not &lsquo;<samp>\</samp>&rsquo; as in DOS). One
example is &lsquo;<samp>(hd0,1)/boot/grub2/grub.cfg</samp>&rsquo;. This means the file
<samp>/boot/grub2/grub.cfg</samp> in the first partition of the first hard
disk. If you omit the device name in an absolute file name, GRUB uses
GRUB&rsquo;s <em>root device</em> implicitly. So if you set the root device to,
say, &lsquo;<samp>(hd1,1)</samp>&rsquo; by the command &lsquo;<samp>set root=(hd1,1)</samp>&rsquo; (see <a href="#set">set</a>),
then <code>/boot/kernel</code> is the same as <code>(hd1,1)/boot/kernel</code>.
</p>
<p>On ZFS filesystem the first path component must be
<var>volume</var>&lsquo;<samp>@</samp>&rsquo;[<var>snapshot</var>].
So &lsquo;<samp>/rootvol@snap-129/boot/grub2/grub.cfg</samp>&rsquo; refers to file
&lsquo;<samp>/boot/grub2/grub.cfg</samp>&rsquo; in snapshot of volume &lsquo;<samp>rootvol</samp>&rsquo; with name
&lsquo;<samp>snap-129</samp>&rsquo;.  Trailing &lsquo;<samp>@</samp>&rsquo; after volume name is mandatory even if
snapshot name is omitted.
</p>

<hr>
<a name="Block-list-syntax"></a>
<div class="header">
<p>
Previous: <a href="#File-name-syntax" accesskey="p" rel="prev">File name syntax</a>, Up: <a href="#Filesystem" accesskey="u" rel="up">Filesystem</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="How-to-specify-block-lists"></a>
<h3 class="section">13.3 How to specify block lists</h3>

<p>A block list is used for specifying a file that doesn&rsquo;t appear in the
filesystem, like a chainloader. The syntax is
<code>[<var>offset</var>]+<var>length</var>[,[<var>offset</var>]+<var>length</var>]&hellip;</code>.
Here is an example:
</p>
<div class="example">
<pre class="example"><code>0+100,200+1,300+300</code>
</pre></div>

<p>This represents that GRUB should read blocks 0 through 99, block 200,
and blocks 300 through 599. If you omit an offset, then GRUB assumes
the offset is zero.
</p>
<p>Like the file name syntax (see <a href="#File-name-syntax">File name syntax</a>), if a blocklist
does not contain a device name, then GRUB uses GRUB&rsquo;s <em>root
device</em>. So <code>(hd0,2)+1</code> is the same as <code>+1</code> when the root
device is &lsquo;<samp>(hd0,2)</samp>&rsquo;.
</p>

<hr>
<a name="Interface"></a>
<div class="header">
<p>
Next: <a href="#Environment" accesskey="n" rel="next">Environment</a>, Previous: <a href="#Filesystem" accesskey="p" rel="prev">Filesystem</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GRUB_0027s-user-interface"></a>
<h2 class="chapter">14 GRUB&rsquo;s user interface</h2>

<p>GRUB has both a simple menu interface for choosing preset entries from a
configuration file, and a highly flexible command-line for performing
any desired combination of boot commands.
</p>
<p>GRUB looks for its configuration file as soon as it is loaded. If one
is found, then the full menu interface is activated using whatever
entries were found in the file. If you choose the <em>command-line</em> menu
option, or if the configuration file was not found, then GRUB drops to
the command-line interface.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Command_002dline-interface" accesskey="1">Command-line interface</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The flexible command-line interface
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Menu-interface" accesskey="2">Menu interface</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The simple menu interface
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Menu-entry-editor" accesskey="3">Menu entry editor</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Editing a menu entry
</td></tr>
</table>

<hr>
<a name="Command_002dline-interface"></a>
<div class="header">
<p>
Next: <a href="#Menu-interface" accesskey="n" rel="next">Menu interface</a>, Up: <a href="#Interface" accesskey="u" rel="up">Interface</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="The-flexible-command_002dline-interface"></a>
<h3 class="section">14.1 The flexible command-line interface</h3>

<p>The command-line interface provides a prompt and after it an editable
text area much like a command-line in Unix or DOS. Each command is
immediately executed after it is entered<a name="DOCF8" href="#FOOT8"><sup>8</sup></a>. The commands (see <a href="#Command_002dline-and-menu-entry-commands">Command-line and menu entry commands</a>) are a
subset of those available in the configuration file, used with exactly
the same syntax.
</p>
<p>Cursor movement and editing of the text on the line can be done via a
subset of the functions available in the Bash shell:
</p>
<dl compact="compact">
<dt><tt class="key">C-f</tt></dt>
<dt><tt class="key">PC right key</tt></dt>
<dd><p>Move forward one character.
</p>
</dd>
<dt><tt class="key">C-b</tt></dt>
<dt><tt class="key">PC left key</tt></dt>
<dd><p>Move back one character.
</p>
</dd>
<dt><tt class="key">C-a</tt></dt>
<dt><tt class="key">HOME</tt></dt>
<dd><p>Move to the start of the line.
</p>
</dd>
<dt><tt class="key">C-e</tt></dt>
<dt><tt class="key">END</tt></dt>
<dd><p>Move the the end of the line.
</p>
</dd>
<dt><tt class="key">C-d</tt></dt>
<dt><tt class="key">DEL</tt></dt>
<dd><p>Delete the character underneath the cursor.
</p>
</dd>
<dt><tt class="key">C-h</tt></dt>
<dt><tt class="key">BS</tt></dt>
<dd><p>Delete the character to the left of the cursor.
</p>
</dd>
<dt><tt class="key">C-k</tt></dt>
<dd><p>Kill the text from the current cursor position to the end of the line.
</p>
</dd>
<dt><tt class="key">C-u</tt></dt>
<dd><p>Kill backward from the cursor to the beginning of the line.
</p>
</dd>
<dt><tt class="key">C-y</tt></dt>
<dd><p>Yank the killed text back into the buffer at the cursor.
</p>
</dd>
<dt><tt class="key">C-p</tt></dt>
<dt><tt class="key">PC up key</tt></dt>
<dd><p>Move up through the history list.
</p>
</dd>
<dt><tt class="key">C-n</tt></dt>
<dt><tt class="key">PC down key</tt></dt>
<dd><p>Move down through the history list.
</p></dd>
</dl>

<p>When typing commands interactively, if the cursor is within or before
the first word in the command-line, pressing the <tt class="key">TAB</tt> key (or
<tt class="key">C-i</tt>) will display a listing of the available commands, and if the
cursor is after the first word, the <kbd><span class="key">TAB</span></kbd> will provide a
completion listing of disks, partitions, and file names depending on the
context. Note that to obtain a list of drives, one must open a
parenthesis, as <code>root (</code>.
</p>
<p>Note that you cannot use the completion functionality in the TFTP
filesystem. This is because TFTP doesn&rsquo;t support file name listing for
the security.
</p>

<hr>
<a name="Menu-interface"></a>
<div class="header">
<p>
Next: <a href="#Menu-entry-editor" accesskey="n" rel="next">Menu entry editor</a>, Previous: <a href="#Command_002dline-interface" accesskey="p" rel="prev">Command-line interface</a>, Up: <a href="#Interface" accesskey="u" rel="up">Interface</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="The-simple-menu-interface"></a>
<h3 class="section">14.2 The simple menu interface</h3>

<p>The menu interface is quite easy to use. Its commands are both
reasonably intuitive and described on screen.
</p>
<p>Basically, the menu interface provides a list of <em>boot entries</em> to
the user to choose from. Use the arrow keys to select the entry of
choice, then press <tt class="key">RET</tt> to run it.  An optional timeout is
available to boot the default entry (the first one if not set), which is
aborted by pressing any key.
</p>
<p>Commands are available to enter a bare command-line by pressing <tt class="key">c</tt>
(which operates exactly like the non-config-file version of GRUB, but
allows one to return to the menu if desired by pressing <tt class="key">ESC</tt>) or to
edit any of the <em>boot entries</em> by pressing <tt class="key">e</tt>.
</p>
<p>If you protect the menu interface with a password (see <a href="#Security">Security</a>),
all you can do is choose an entry by pressing <tt class="key">RET</tt>, or press
<tt class="key">p</tt> to enter the password.
</p>

<hr>
<a name="Menu-entry-editor"></a>
<div class="header">
<p>
Previous: <a href="#Menu-interface" accesskey="p" rel="prev">Menu interface</a>, Up: <a href="#Interface" accesskey="u" rel="up">Interface</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Editing-a-menu-entry"></a>
<h3 class="section">14.3 Editing a menu entry</h3>

<p>The menu entry editor looks much like the main menu interface, but the
lines in the menu are individual commands in the selected entry instead
of entry names.
</p>
<p>If an <tt class="key">ESC</tt> is pressed in the editor, it aborts all the changes made
to the configuration entry and returns to the main menu interface.
</p>
<p>Each line in the menu entry can be edited freely, and you can add new lines
by pressing <tt class="key">RET</tt> at the end of a line.  To boot the edited entry, press
<tt class="key">Ctrl-x</tt>.
</p>
<p>Although GRUB unfortunately does not support <em>undo</em>, you can do almost
the same thing by just returning to the main menu using <tt class="key">ESC</tt>.
</p>

<hr>
<a name="Environment"></a>
<div class="header">
<p>
Next: <a href="#Commands" accesskey="n" rel="next">Commands</a>, Previous: <a href="#Interface" accesskey="p" rel="prev">Interface</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="GRUB-environment-variables"></a>
<h2 class="chapter">15 GRUB environment variables</h2>

<p>GRUB supports environment variables which are rather like those offered by
all Unix-like systems.  Environment variables have a name, which is unique
and is usually a short identifier, and a value, which is an arbitrary string
of characters.  They may be set (see <a href="#set">set</a>), unset (see <a href="#unset">unset</a>), or
looked up (see <a href="#Shell_002dlike-scripting">Shell-like scripting</a>) by name.
</p>
<p>A number of environment variables have special meanings to various parts of
GRUB.  Others may be used freely in GRUB configuration files.
</p>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#Special-environment-variables" accesskey="1">Special environment variables</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#Environment-block" accesskey="2">Environment block</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="Special-environment-variables"></a>
<div class="header">
<p>
Next: <a href="#Environment-block" accesskey="n" rel="next">Environment block</a>, Up: <a href="#Environment" accesskey="u" rel="up">Environment</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="Special-environment-variables-1"></a>
<h3 class="section">15.1 Special environment variables</h3>

<p>These variables have special meaning to GRUB.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="#biosnum" accesskey="1">biosnum</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#check_005fappended_005fsignatures" accesskey="2">check_appended_signatures</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#check_005fsignatures" accesskey="3">check_signatures</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#chosen" accesskey="4">chosen</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#cmdpath" accesskey="5">cmdpath</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#color_005fhighlight" accesskey="6">color_highlight</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#color_005fnormal" accesskey="7">color_normal</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#config_005fdirectory" accesskey="8">config_directory</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#config_005ffile" accesskey="9">config_file</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#debug">debug</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#default">default</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#fallback">fallback</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#gfxmode">gfxmode</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#gfxpayload">gfxpayload</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#gfxterm_005ffont">gfxterm_font</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#grub_005fcpu">grub_cpu</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#grub_005fplatform">grub_platform</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#icondir">icondir</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#lang">lang</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#locale_005fdir">locale_dir</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#menu_005fcolor_005fhighlight">menu_color_highlight</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#menu_005fcolor_005fnormal">menu_color_normal</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fboot_005ffile">net_<var>&lt;interface&gt;</var>_boot_file</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fdhcp_005fserver_005fname">net_<var>&lt;interface&gt;</var>_dhcp_server_name</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fdomain">net_<var>&lt;interface&gt;</var>_domain</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fextensionspath">net_<var>&lt;interface&gt;</var>_extensionspath</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fhostname">net_<var>&lt;interface&gt;</var>_hostname</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fip">net_<var>&lt;interface&gt;</var>_ip</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fmac">net_<var>&lt;interface&gt;</var>_mac</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005fnext_005fserver">net_<var>&lt;interface&gt;</var>_next_server</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005f_003cinterface_003e_005frootpath">net_<var>&lt;interface&gt;</var>_rootpath</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005fdefault_005finterface">net_default_interface</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005fdefault_005fip">net_default_ip</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005fdefault_005fmac">net_default_mac</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#net_005fdefault_005fserver">net_default_server</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#pager">pager</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#prefix">prefix</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#pxe_005fblksize">pxe_blksize</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#pxe_005fdefault_005fgateway">pxe_default_gateway</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#pxe_005fdefault_005fserver">pxe_default_server</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#root">root</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#superusers">superusers</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#theme">theme</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#timeout">timeout</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="#timeout_005fstyle">timeout_style</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
</table>

<hr>
<a name="biosnum"></a>
<div class="header">
<p>
Next: <a href="#check_005fappended_005fsignatures" accesskey="n" rel="next">check_appended_signatures</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="biosnum-1"></a>
<h4 class="subsection">15.1.1 biosnum</h4>

<p>When chain-loading another boot loader (see <a href="#Chain_002dloading">Chain-loading</a>), GRUB may
need to know what BIOS drive number corresponds to the root device
(see <a href="#root">root</a>) so that it can set up registers properly.  If the
<var>biosnum</var> variable is set, it overrides GRUB&rsquo;s own means of guessing
this.
</p>
<p>For an alternative approach which also changes BIOS drive mappings for the
chain-loaded system, see <a href="#drivemap">drivemap</a>.
</p>

<hr>
<a name="check_005fappended_005fsignatures"></a>
<div class="header">
<p>
Next: <a href="#check_005fsignatures" accesskey="n" rel="next">check_signatures</a>, Previous: <a href="#biosnum" accesskey="p" rel="prev">biosnum</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="check_005fappended_005fsignatures-1"></a>
<h4 class="subsection">15.1.2 check_appended_signatures</h4>

<p>This variable controls whether GRUB enforces appended signature validation on
certain loaded files. See <a href="#Using-appended-signatures">Using appended signatures</a>.
</p>

<hr>
<a name="check_005fsignatures"></a>
<div class="header">
<p>
Next: <a href="#chosen" accesskey="n" rel="next">chosen</a>, Previous: <a href="#check_005fappended_005fsignatures" accesskey="p" rel="prev">check_appended_signatures</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="check_005fsignatures-1"></a>
<h4 class="subsection">15.1.3 check_signatures</h4>

<p>This variable controls whether GRUB enforces GPG-style digital signature
validation on loaded files. See <a href="#Using-GPG_002dstyle-digital-signatures">Using GPG-style digital signatures</a>.
</p>
<hr>
<a name="chosen"></a>
<div class="header">
<p>
Next: <a href="#cmdpath" accesskey="n" rel="next">cmdpath</a>, Previous: <a href="#check_005fsignatures" accesskey="p" rel="prev">check_signatures</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="chosen-1"></a>
<h4 class="subsection">15.1.4 chosen</h4>

<p>When executing a menu entry, GRUB sets the <var>chosen</var> variable to the
title of the entry being executed.
</p>
<p>If the menu entry is in one or more submenus, then <var>chosen</var> is set to
the titles of each of the submenus starting from the top level followed by
the title of the menu entry itself, separated by &lsquo;<samp>&gt;</samp>&rsquo;.
</p>

<hr>
<a name="cmdpath"></a>
<div class="header">
<p>
Next: <a href="#color_005fhighlight" accesskey="n" rel="next">color_highlight</a>, Previous: <a href="#chosen" accesskey="p" rel="prev">chosen</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="cmdpath-1"></a>
<h4 class="subsection">15.1.5 cmdpath</h4>

<p>The location from which <samp>core.img</samp> was loaded as an absolute
directory name (see <a href="#File-name-syntax">File name syntax</a>).  This is set by GRUB at
startup based on information returned by platform firmware.  Not every
platform provides this information and some may return only device
without path name.
</p>

<hr>
<a name="color_005fhighlight"></a>
<div class="header">
<p>
Next: <a href="#color_005fnormal" accesskey="n" rel="next">color_normal</a>, Previous: <a href="#cmdpath" accesskey="p" rel="prev">cmdpath</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="color_005fhighlight-1"></a>
<h4 class="subsection">15.1.6 color_highlight</h4>

<p>This variable contains the &ldquo;highlight&rdquo; foreground and background terminal
colors, separated by a slash (&lsquo;<samp>/</samp>&rsquo;).  Setting this variable changes
those colors.  For the available color names, see <a href="#color_005fnormal">color_normal</a>.
</p>
<p>The default is &lsquo;<samp>black/light-gray</samp>&rsquo;.
</p>

<hr>
<a name="color_005fnormal"></a>
<div class="header">
<p>
Next: <a href="#config_005fdirectory" accesskey="n" rel="next">config_directory</a>, Previous: <a href="#color_005fhighlight" accesskey="p" rel="prev">color_highlight</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="color_005fnormal-1"></a>
<h4 class="subsection">15.1.7 color_normal</h4>

<p>This variable contains the &ldquo;normal&rdquo; foreground and background terminal
colors, separated by a slash (&lsquo;<samp>/</samp>&rsquo;).  Setting this variable changes
those colors.  Each color must be a name from the following list:
</p>
<ul>
<li> black
</li><li> blue
</li><li> green
</li><li> cyan
</li><li> red
</li><li> magenta
</li><li> brown
</li><li> light-gray
</li><li> dark-gray
</li><li> light-blue
</li><li> light-green
</li><li> light-cyan
</li><li> light-red
</li><li> light-magenta
</li><li> yellow
</li><li> white
</li></ul>

<p>The default is &lsquo;<samp>light-gray/black</samp>&rsquo;.
</p>
<p>The color support support varies from terminal to terminal.
</p>
<p>&lsquo;<samp>morse</samp>&rsquo; has no color support at all.
</p>
<p>&lsquo;<samp>mda_text</samp>&rsquo; color support is limited to highlighting by
black/white reversal.
</p>
<p>&lsquo;<samp>console</samp>&rsquo; on ARC, EMU and IEEE1275, &lsquo;<samp>serial_*</samp>&rsquo; and
&lsquo;<samp>spkmodem</samp>&rsquo; are governed by terminfo and support
only 8 colors if in modes &lsquo;<samp>vt100-color</samp>&rsquo; (default for console on emu),
&lsquo;<samp>arc</samp>&rsquo; (default for console on ARC), &lsquo;<samp>ieee1275</samp>&rsquo; (default
for console on IEEE1275). When in mode &lsquo;<samp>vt100</samp>&rsquo;
then the color support is limited to highlighting by black/white
reversal. When in mode &lsquo;<samp>dumb</samp>&rsquo; there is no color support.
</p>
<p>When console supports no colors this setting is ignored.
When console supports 8 colors, then the colors from the
second half of the previous list are mapped to the
matching colors of first half.
</p>
<p>&lsquo;<samp>console</samp>&rsquo; on EFI and BIOS and &lsquo;<samp>vga_text</samp>&rsquo; support all 16 colors.
</p>
<p>&lsquo;<samp>gfxterm</samp>&rsquo; supports all 16 colors and would be theoretically extendable
to support whole rgb24 palette but currently there is no compelling reason
to go beyond the current 16 colors.
</p>

<hr>
<a name="config_005fdirectory"></a>
<div class="header">
<p>
Next: <a href="#config_005ffile" accesskey="n" rel="next">config_file</a>, Previous: <a href="#color_005fnormal" accesskey="p" rel="prev">color_normal</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="config_005fdirectory-1"></a>
<h4 class="subsection">15.1.8 config_directory</h4>

<p>This variable is automatically set by GRUB to the directory part of
current configuration file name (see <a href="#config_005ffile">config_file</a>).
</p>

<hr>
<a name="config_005ffile"></a>
<div class="header">
<p>
Next: <a href="#debug" accesskey="n" rel="next">debug</a>, Previous: <a href="#config_005fdirectory" accesskey="p" rel="prev">config_directory</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="config_005ffile-1"></a>
<h4 class="subsection">15.1.9 config_file</h4>

<p>This variable is automatically set by GRUB to the name of configuration file that is being
processed by commands <code>configfile</code> (see <a href="#configfile">configfile</a>) or <code>normal</code>
(see <a href="#normal">normal</a>).  It is restored to the previous value when command completes.
</p>

<hr>
<a name="debug"></a>
<div class="header">
<p>
Next: <a href="#default" accesskey="n" rel="next">default</a>, Previous: <a href="#config_005ffile" accesskey="p" rel="prev">config_file</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="debug-1"></a>
<h4 class="subsection">15.1.10 debug</h4>

<p>This variable may be set to enable debugging output from various components
of GRUB.  The value is a list of debug facility names separated by
whitespace or &lsquo;<samp>,</samp>&rsquo;, or &lsquo;<samp>all</samp>&rsquo; to enable all available debugging
output. The facility names are the first argument to grub_dprintf. Consult
source for more details.
</p>

<hr>
<a name="default"></a>
<div class="header">
<p>
Next: <a href="#fallback" accesskey="n" rel="next">fallback</a>, Previous: <a href="#debug" accesskey="p" rel="prev">debug</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="default-1"></a>
<h4 class="subsection">15.1.11 default</h4>

<p>If this variable is set, it identifies a menu entry that should be
selected by default, possibly after a timeout (see <a href="#timeout">timeout</a>).  The
entry may be identified by number (starting from 0 at each level of
the hierarchy), by title, or by id.
</p>
<p>For example, if you have:
</p>
<pre class="verbatim">menuentry 'Example GNU/Linux distribution' --class gnu-linux --id example-gnu-linux {
	...
}
</pre>
<p>then you can make this the default using:
</p>
<div class="example">
<pre class="example">default=example-gnu-linux
</pre></div>

<p>If the entry is in a submenu, then it must be identified using the
number, title, or id of each of the submenus starting from the top
level, followed by the number, title, or id of the menu entry itself,
with each element separated by &lsquo;<samp>&gt;</samp>&rsquo;.  For example, take the
following menu structure:
</p>
<div class="example">
<pre class="example">GNU/Hurd --id gnu-hurd
  Standard Boot --id=gnu-hurd-std
  Rescue shell --id=gnu-hurd-rescue
Other platforms --id=other
  Minix --id=minix
    Version 3.4.0 --id=minix-3.4.0
    Version 3.3.0 --id=minix-3.3.0
  GRUB Invaders --id=grub-invaders
</pre></div>

<p>The more recent release of Minix would then be identified as
&lsquo;<samp>Other platforms&gt;Minix&gt;Version 3.4.0</samp>&rsquo;, or as &lsquo;<samp>1&gt;0&gt;0</samp>&rsquo;, or as
&lsquo;<samp>other&gt;minix&gt;minix-3.4.0</samp>&rsquo;.
</p>
<p>This variable is often set by &lsquo;<samp>GRUB_DEFAULT</samp>&rsquo; (see <a href="#Simple-configuration">Simple configuration</a>), <code>grub2-set-default</code>, or <code>grub2-reboot</code>.
</p>

<hr>
<a name="fallback"></a>
<div class="header">
<p>
Next: <a href="#gfxmode" accesskey="n" rel="next">gfxmode</a>, Previous: <a href="#default" accesskey="p" rel="prev">default</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="fallback-1"></a>
<h4 class="subsection">15.1.12 fallback</h4>

<p>If this variable is set, it identifies a menu entry that should be selected
if the default menu entry fails to boot.  Entries are identified in the same
way as for &lsquo;<samp>default</samp>&rsquo; (see <a href="#default">default</a>).
</p>

<hr>
<a name="gfxmode"></a>
<div class="header">
<p>
Next: <a href="#gfxpayload" accesskey="n" rel="next">gfxpayload</a>, Previous: <a href="#fallback" accesskey="p" rel="prev">fallback</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="gfxmode-1"></a>
<h4 class="subsection">15.1.13 gfxmode</h4>

<p>If this variable is set, it sets the resolution used on the &lsquo;<samp>gfxterm</samp>&rsquo;
graphical terminal.  Note that you can only use modes which your graphics
card supports via VESA BIOS Extensions (VBE), so for example native LCD
panel resolutions may not be available.  The default is &lsquo;<samp>auto</samp>&rsquo;, which
selects a platform-specific default that should look reasonable. Supported
modes can be listed by &lsquo;<samp>videoinfo</samp>&rsquo; command in GRUB.
</p>
<p>The resolution may be specified as a sequence of one or more modes,
separated by commas (&lsquo;<samp>,</samp>&rsquo;) or semicolons (&lsquo;<samp>;</samp>&rsquo;); each will be tried
in turn until one is found.  Each mode should be either &lsquo;<samp>auto</samp>&rsquo;,
&lsquo;<samp><var>width</var>x<var>height</var></samp>&rsquo;, or
&lsquo;<samp><var>width</var>x<var>height</var>x<var>depth</var></samp>&rsquo;.
</p>

<hr>
<a name="gfxpayload"></a>
<div class="header">
<p>
Next: <a href="#gfxterm_005ffont" accesskey="n" rel="next">gfxterm_font</a>, Previous: <a href="#gfxmode" accesskey="p" rel="prev">gfxmode</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="gfxpayload-1"></a>
<h4 class="subsection">15.1.14 gfxpayload</h4>

<p>If this variable is set, it controls the video mode in which the Linux
kernel starts up, replacing the &lsquo;<samp>vga=</samp>&rsquo; boot option (see <a href="#linux">linux</a>).  It
may be set to &lsquo;<samp>text</samp>&rsquo; to force the Linux kernel to boot in normal text
mode, &lsquo;<samp>keep</samp>&rsquo; to preserve the graphics mode set using &lsquo;<samp>gfxmode</samp>&rsquo;, or
any of the permitted values for &lsquo;<samp>gfxmode</samp>&rsquo; to set a particular graphics
mode (see <a href="#gfxmode">gfxmode</a>).
</p>
<p>Depending on your kernel, your distribution, your graphics card, and the
phase of the moon, note that using this option may cause GNU/Linux to suffer
from various display problems, particularly during the early part of the
boot sequence.  If you have problems, set this variable to &lsquo;<samp>text</samp>&rsquo; and
GRUB will tell Linux to boot in normal text mode.
</p>
<p>The default is platform-specific.  On platforms with a native text mode
(such as PC BIOS platforms), the default is &lsquo;<samp>text</samp>&rsquo;.  Otherwise the
default may be &lsquo;<samp>auto</samp>&rsquo; or a specific video mode.
</p>
<p>This variable is often set by &lsquo;<samp>GRUB_GFXPAYLOAD_LINUX</samp>&rsquo; (see <a href="#Simple-configuration">Simple configuration</a>).
</p>

<hr>
<a name="gfxterm_005ffont"></a>
<div class="header">
<p>
Next: <a href="#grub_005fcpu" accesskey="n" rel="next">grub_cpu</a>, Previous: <a href="#gfxpayload" accesskey="p" rel="prev">gfxpayload</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="gfxterm_005ffont-1"></a>
<h4 class="subsection">15.1.15 gfxterm_font</h4>

<p>If this variable is set, it names a font to use for text on the
&lsquo;<samp>gfxterm</samp>&rsquo; graphical terminal.  Otherwise, &lsquo;<samp>gfxterm</samp>&rsquo; may use any
available font.
</p>

<hr>
<a name="grub_005fcpu"></a>
<div class="header">
<p>
Next: <a href="#grub_005fplatform" accesskey="n" rel="next">grub_platform</a>, Previous: <a href="#gfxterm_005ffont" accesskey="p" rel="prev">gfxterm_font</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="grub_005fcpu-1"></a>
<h4 class="subsection">15.1.16 grub_cpu</h4>

<p>In normal mode (see <a href="#normal">normal</a>), GRUB sets the &lsquo;<samp>grub_cpu</samp>&rsquo; variable to
the CPU type for which GRUB was built (e.g. &lsquo;<samp>i386</samp>&rsquo; or &lsquo;<samp>powerpc</samp>&rsquo;).
</p>

<hr>
<a name="grub_005fplatform"></a>
<div class="header">
<p>
Next: <a href="#icondir" accesskey="n" rel="next">icondir</a>, Previous: <a href="#grub_005fcpu" accesskey="p" rel="prev">grub_cpu</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="grub_005fplatform-1"></a>
<h4 class="subsection">15.1.17 grub_platform</h4>

<p>In normal mode (see <a href="#normal">normal</a>), GRUB sets the &lsquo;<samp>grub_platform</samp>&rsquo; variable
to the platform for which GRUB was built (e.g. &lsquo;<samp>pc</samp>&rsquo; or &lsquo;<samp>efi</samp>&rsquo;).
</p>

<hr>
<a name="icondir"></a>
<div class="header">
<p>
Next: <a href="#lang" accesskey="n" rel="next">lang</a>, Previous: <a href="#grub_005fplatform" accesskey="p" rel="prev">grub_platform</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="icondir-1"></a>
<h4 class="subsection">15.1.18 icondir</h4>

<p>If this variable is set, it names a directory in which the GRUB graphical
menu should look for icons after looking in the theme&rsquo;s &lsquo;<samp>icons</samp>&rsquo;
directory.  See <a href="#Theme-file-format">Theme file format</a>.
</p>

<hr>
<a name="lang"></a>
<div class="header">
<p>
Next: <a href="#locale_005fdir" accesskey="n" rel="next">locale_dir</a>, Previous: <a href="#icondir" accesskey="p" rel="prev">icondir</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="lang-1"></a>
<h4 class="subsection">15.1.19 lang</h4>

<p>If this variable is set, it names the language code that the
<code>gettext</code> command (see <a href="#gettext">gettext</a>) uses to translate strings.  For
example, French would be named as &lsquo;<samp>fr</samp>&rsquo;, and Simplified Chinese as
&lsquo;<samp>zh_CN</samp>&rsquo;.
</p>
<p><code>grub2-mkconfig</code> (see <a href="#Simple-configuration">Simple configuration</a>) will try to set a
reasonable default for this variable based on the system locale.
</p>

<hr>
<a name="locale_005fdir"></a>
<div class="header">
<p>
Next: <a href="#menu_005fcolor_005fhighlight" accesskey="n" rel="next">menu_color_highlight</a>, Previous: <a href="#lang" accesskey="p" rel="prev">lang</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="locale_005fdir-1"></a>
<h4 class="subsection">15.1.20 locale_dir</h4>

<p>If this variable is set, it names the directory where translation files may
be found (see <a href="#gettext">gettext</a>), usually <samp>/boot/grub2/locale</samp>.  Otherwise,
internationalization is disabled.
</p>
<p><code>grub2-mkconfig</code> (see <a href="#Simple-configuration">Simple configuration</a>) will set a reasonable
default for this variable if internationalization is needed and any
translation files are available.
</p>

<hr>
<a name="menu_005fcolor_005fhighlight"></a>
<div class="header">
<p>
Next: <a href="#menu_005fcolor_005fnormal" accesskey="n" rel="next">menu_color_normal</a>, Previous: <a href="#locale_005fdir" accesskey="p" rel="prev">locale_dir</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="menu_005fcolor_005fhighlight-1"></a>
<h4 class="subsection">15.1.21 menu_color_highlight</h4>

<p>This variable contains the foreground and background colors to be used for
the highlighted menu entry, separated by a slash (&lsquo;<samp>/</samp>&rsquo;).  Setting this
variable changes those colors.  For the available color names,
see <a href="#color_005fnormal">color_normal</a>.
</p>
<p>The default is the value of &lsquo;<samp>color_highlight</samp>&rsquo;
(see <a href="#color_005fhighlight">color_highlight</a>).
</p>

<hr>
<a name="menu_005fcolor_005fnormal"></a>
<div class="header">
<p>
Next: <a href="#net_005f_003cinterface_003e_005fboot_005ffile" accesskey="n" rel="next">net_<var>&lt;interface&gt;</var>_boot_file</a>, Previous: <a href="#menu_005fcolor_005fhighlight" accesskey="p" rel="prev">menu_color_highlight</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="menu_005fcolor_005fnormal-1"></a>
<h4 class="subsection">15.1.22 menu_color_normal</h4>

<p>This variable contains the foreground and background colors to be used for
non-highlighted menu entries, separated by a slash (&lsquo;<samp>/</samp>&rsquo;).  Setting this
variable changes those colors.  For the available color names,
see <a href="#color_005fnormal">color_normal</a>.
</p>
<p>The default is the value of &lsquo;<samp>color_normal</samp>&rsquo; (see <a href="#color_005fnormal">color_normal</a>).
</p>

<hr>
<a name="net_005f_003cinterface_003e_005fboot_005ffile"></a>
<div class="header">
<p>
Next: <a href="#net_005f_003cinterface_003e_005fdhcp_005fserver_005fname" accesskey="n" rel="next">net_<var>&lt;interface&gt;</var>_dhcp_server_name</a>, Previous: <a href="#menu_005fcolor_005fnormal" accesskey="p" rel="prev">menu_color_normal</a>, Up: <a href="#Special-environment-variables" accesskey="u" rel="up">Special environment variables</a> &nbsp; [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="#Index" title="Index" rel="index">Index</a>]</p>
</div>
<a name="net_005f_003cinterface_003e_005fboot_005ffile-1"></a>
<h4 class="subsection">15.1.23 net_<var>&lt;interface&gt;</var>_boot_file</h4>