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\input texinfo
@c -*-texinfo-*-
@c %**start of header
@setfilename grub.info
@include version.texi
@settitle GNU GRUB Manual @value{VERSION}
@c Unify all our little indices for now.
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@footnotestyle separate
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@copying
This manual is for GNU GRUB (version @value{VERSION},
@value{UPDATED}).

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Copyright @copyright{} 1999,2000,2001,2002,2004,2006,2008,2009,2010,2011,2012,2013 Free Software Foundation, Inc.
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@quotation
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.
@end quotation
@end copying

@dircategory Kernel
@direntry
* GRUB: (grub).                 The GRand Unified Bootloader
* grub-install: (grub)Invoking grub-install.    Install GRUB on your drive
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* grub-mkconfig: (grub)Invoking grub-mkconfig.  Generate GRUB configuration
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* grub-mkpasswd-pbkdf2: (grub)Invoking grub-mkpasswd-pbkdf2.
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* grub-mkrelpath: (grub)Invoking grub-mkrelpath.
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* grub-mkrescue: (grub)Invoking grub-mkrescue.  Make a GRUB rescue image
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* grub-mount: (grub)Invoking grub-mount.        Mount a file system using GRUB
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* grub-probe: (grub)Invoking grub-probe.        Probe device information
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* grub-script-check: (grub)Invoking grub-script-check.
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@end direntry

@setchapternewpage odd

@titlepage
@sp 10
@title the GNU GRUB manual
@subtitle The GRand Unified Bootloader, version @value{VERSION}, @value{UPDATED}.
@author Gordon Matzigkeit
@author Yoshinori K. Okuji
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@author Colin Watson
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@author Colin D. Bennett
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@c The following two commands start the copyright page.
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@c Output the table of contents at the beginning.
@contents

@finalout
@headings double

@ifnottex
@node Top
@top GNU GRUB manual

This is the documentation of GNU GRUB, the GRand Unified Bootloader,
a flexible and powerful boot loader program for a wide range of
architectures.

This edition documents version @value{VERSION}.

@insertcopying
@end ifnottex

@menu
* Introduction::                Capturing the spirit of GRUB
* Naming convention::           Names of your drives in GRUB
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* OS-specific notes about grub tools:: 
                                Some notes about OS-specific behaviour of GRUB
                                tools
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* Installation::                Installing GRUB on your drive
* Booting::                     How to boot different operating systems
* Configuration::               Writing your own configuration file
90
* Theme file format::           Format of GRUB theme files
91 92
* Network::                     Downloading OS images from a network
* Serial terminal::             Using GRUB via a serial line
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* Vendor power-on keys::        Changing GRUB behaviour on vendor power-on keys
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* Images::                      GRUB image files
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* Core image size limitation::  GRUB image files size limitations
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* Filesystem::                  Filesystem syntax and semantics
* Interface::                   The menu and the command-line
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* Environment::                 GRUB environment variables
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* Commands::                    The list of available builtin commands
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* Internationalisation::        Topics relating to language support
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* Security::                    Authentication, authorisation, and signatures
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* Platform limitations::        The list of platform-specific limitations
* Platform-specific operations:: Platform-specific operations
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* Supported kernels::           The list of supported kernels
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* Troubleshooting::             Error messages produced by GRUB
* Invoking grub-install::       How to use the GRUB installer
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* Invoking grub-mkconfig::      Generate a GRUB configuration file
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* Invoking grub-mkpasswd-pbkdf2::
                                Generate GRUB password hashes
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* Invoking grub-mkrelpath::     Make system path relative to its root
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* Invoking grub-mkrescue::      Make a GRUB rescue image
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* Invoking grub-mount::         Mount a file system using GRUB
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* Invoking grub-probe::         Probe device information for GRUB
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* Invoking grub-script-check::  Check GRUB script file for syntax errors
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* Obtaining and Building GRUB:: How to obtain and build GRUB
* Reporting bugs::              Where you should send a bug report
* Future::                      Some future plans on GRUB
* Copying This Manual::         Copying This Manual
* Index::
@end menu


@node Introduction
@chapter Introduction to GRUB

@menu
* Overview::                    What exactly GRUB is and how to use it
* History::                     From maggot to house fly
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* Changes from GRUB Legacy::    Differences from previous versions
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* Features::                    GRUB features
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* Role of a boot loader::       The role of a boot loader
@end menu


@node Overview
@section Overview

Briefly, a @dfn{boot loader} is the first software program that runs when
a computer starts.  It is responsible for loading and transferring
control to an operating system @dfn{kernel} software (such as Linux or
GNU Mach).  The kernel, in turn, initializes the rest of the operating
system (e.g. a GNU system).

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@footnote{@dfn{chain-load} is the mechanism for loading
unsupported operating systems by loading another boot loader. It is
typically used for loading DOS or Windows.}. 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.

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.

When booting with GRUB, you can use either a command-line interface
(@pxref{Command-line interface}), or a menu interface (@pxref{Menu
interface}). 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
(@pxref{Configuration}). While in the menu, you can switch to the
command-line mode, and vice-versa. You can even edit menu entries
before using them.

In the following chapters, you will learn how to specify a drive, a
partition, and a file name (@pxref{Naming convention}) to GRUB, how to
install GRUB on your drive (@pxref{Installation}), and how to boot your
OSes (@pxref{Booting}), step by step.


@node History
@section History of GRUB

GRUB originated in 1995 when Erich Boleyn was trying to boot the GNU
Hurd with the University of Utah's Mach 4 microkernel (now known as GNU
Mach).  Erich and Brian Ford designed the Multiboot Specification
(@pxref{Top, Multiboot Specification, Motivation, multiboot, The Multiboot
Specification}), because they were determined not to add to the large
number of mutually-incompatible PC boot methods.

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.

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. @xref{Obtaining and Building
GRUB}, for more information.

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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.

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.

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@node Changes from GRUB Legacy
@section Differences from previous versions

GRUB 2 is a rewrite of GRUB (@pxref{History}), 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.

@itemize @bullet
@item
The configuration file has a new name (@file{grub.cfg} rather than
@file{menu.lst} or @file{grub.conf}), new syntax (@pxref{Configuration}) and
many new commands (@pxref{Commands}).  Configuration cannot be copied over
directly, although most GRUB Legacy users should not find the syntax too
surprising.

@item
@file{grub.cfg} is typically automatically generated by
@command{grub-mkconfig} (@pxref{Simple configuration}).  This makes it
easier to handle versioned kernel upgrades.

@item
Partition numbers in GRUB device names now start at 1, not 0 (@pxref{Naming
convention}).

@item
The configuration file is now written in something closer to a full
scripting language: variables, conditionals, and loops are available.

@item
A small amount of persistent storage is available across reboots, using the
@command{save_env} and @command{load_env} commands in GRUB and the
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@command{grub-editenv} utility.  This is not available in all configurations
(@pxref{Environment block}).
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@item
GRUB 2 has more reliable ways to find its own files and those of target
kernels on multiple-disk systems, and has commands (@pxref{search}) to find
devices using file system labels or Universally Unique Identifiers (UUIDs).

@item
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.

@item
Many more file systems are supported, including but not limited to ext4,
HFS+, and NTFS.

@item
GRUB 2 can read files directly from LVM and RAID devices.

@item
A graphical terminal and a graphical menu system are available.

@item
GRUB 2's interface can be translated, including menu entry names.

@item
The image files (@pxref{Images}) that make up GRUB have been reorganised;
Stage 1, Stage 1.5, and Stage 2 are no more.

@item
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.
@end itemize


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@node Features
@section GRUB features

The primary requirement for GRUB is that it be compliant with the
@dfn{Multiboot Specification}, which is described in @ref{Top, Multiboot
Specification, Motivation, multiboot, The Multiboot Specification}.

The other goals, listed in approximate order of importance, are:

@itemize @bullet{}
@item
Basic functions must be straightforward for end-users.

@item
Rich functionality to support kernel experts and designers.

@item
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.
@end itemize

Except for specific compatibility modes (chain-loading and the Linux
@dfn{piggyback} 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.

In addition to the requirements above, GRUB has the following features
(note that the Multiboot Specification doesn't require all the features
that GRUB supports):

@table @asis
@item Recognize multiple executable formats
Support many of the @dfn{a.out} variants plus @dfn{ELF}. Symbol
tables are also loaded.

@item Support non-Multiboot kernels
Support many of the various free 32-bit kernels that lack Multiboot
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compliance (primarily FreeBSD, NetBSD@footnote{The NetBSD/i386 kernel
is Multiboot-compliant, but lacks support for Multiboot modules.},
OpenBSD, and Linux). Chain-loading of other boot loaders is also
supported.
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@item Load multiples modules
Fully support the Multiboot feature of loading multiple modules.

@item Load a configuration file
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 (@pxref{Commands}) are a superset of those supported on the
command-line. An example configuration file is provided in
@ref{Configuration}.

@item Provide a menu interface
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.

@item Have a flexible command-line interface
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.

The list of commands (@pxref{Commands}) are a subset of those supported
for configuration files. Editing commands closely resembles the Bash
command-line (@pxref{Command Line Editing, Bash, Command Line Editing,
features, Bash Features}), with @key{TAB}-completion of commands,
devices, partitions, and files in a directory depending on context.

@item Support multiple filesystem types
Support multiple filesystem types transparently, plus a useful explicit
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blocklist notation. The currently supported filesystem types are @dfn{Amiga
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Fast FileSystem (AFFS)}, @dfn{AtheOS fs}, @dfn{BeFS},
@dfn{BtrFS} (including raid0, raid1, raid10, gzip and lzo),
@dfn{cpio} (little- and big-endian bin, odc and newc variants),
@dfn{Linux ext2/ext3/ext4}, @dfn{DOS FAT12/FAT16/FAT32}, @dfn{exFAT}, @dfn{HFS},
@dfn{HFS+}, @dfn{ISO9660} (including Joliet, Rock-ridge and multi-chunk files),
@dfn{JFS}, @dfn{Minix fs} (versions 1, 2 and 3), @dfn{nilfs2},
@dfn{NTFS} (including compression), @dfn{ReiserFS}, @dfn{ROMFS},
@dfn{Amiga Smart FileSystem (SFS)}, @dfn{Squash4}, @dfn{tar}, @dfn{UDF},
@dfn{BSD UFS/UFS2}, @dfn{XFS}, and @dfn{ZFS} (including lzjb, gzip,
zle, mirror, stripe, raidz1/2/3 and encryption in AES-CCM and AES-GCM).
@xref{Filesystem}, for more information.
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@item Support automatic decompression
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Can decompress files which were compressed by @command{gzip} or
@command{xz}@footnote{Only CRC32 data integrity check is supported (xz default
is CRC64 so one should use --check=crc32 option). LZMA BCJ filters are
supported.}. This function is both automatic and transparent to the user
(i.e. all functions operate upon the uncompressed contents of the specified
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files). This greatly reduces a file size and loading time, a
particularly great benefit for floppies.@footnote{There are a few
pathological cases where loading a very badly organized ELF kernel might
take longer, but in practice this never happen.}

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.

@item Access data on any installed device
Support reading data from any or all floppies or hard disk(s) recognized
by the BIOS, independent of the setting of the root device.

@item Be independent of drive geometry translations
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's configuration.

@item Detect all installed @sc{ram}
GRUB can generally find all the installed @sc{ram} on a PC-compatible
machine. It uses an advanced BIOS query technique for finding all
memory regions. As described on the Multiboot Specification (@pxref{Top,
Multiboot Specification, Motivation, multiboot, The Multiboot
Specification}), not all kernels make use of this information, but GRUB
provides it for those who do.

@item Support Logical Block Address mode
In traditional disk calls (called @dfn{CHS mode}), 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'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 (@dfn{LBA}) mode. GRUB
automatically detects if LBA mode is available and uses it if
available. In LBA mode, GRUB can access the entire disk.

@item Support network booting
GRUB is basically a disk-based boot loader but also has network
support. You can load OS images from a network by using the @dfn{TFTP}
protocol.

@item Support remote terminals
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.
@end table


@node Role of a boot loader
@section The role of a boot loader

The following is a quotation from Gordon Matzigkeit, a GRUB fanatic:

@quotation
Some people like to acknowledge both the operating system and kernel when
they talk about their computers, so they might say they use
``GNU/Linux'' or ``GNU/Hurd''.  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 ``Linux systems.''

I, personally, believe that this is a grave injustice, because the
@emph{boot loader} is the most important software of all. I used to
refer to the above systems as either ``LILO''@footnote{The LInux LOader,
a boot loader that everybody uses, but nobody likes.} or ``GRUB''
systems.

Unfortunately, nobody ever understood what I was talking about; now I
just use the word ``GNU'' as a pseudonym for GRUB.

So, if you ever hear people talking about their alleged ``GNU'' systems,
remember that they are actually paying homage to the best boot loader
around@dots{} GRUB!
@end quotation

We, the GRUB maintainers, do not (usually) encourage Gordon'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.


@node Naming convention
@chapter Naming convention

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.

Look at the following examples and explanations:

@example
(fd0)
@end example

First of all, GRUB requires that the device name be enclosed with
@samp{(} and @samp{)}. The @samp{fd} part means that it is a floppy
disk. The number @samp{0} is the drive number, which is counted from
@emph{zero}. This expression means that GRUB will use the whole floppy
disk.

@example
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(hd0,msdos2)
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@end example

Here, @samp{hd} means it is a hard disk drive. The first integer
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@samp{0} indicates the drive number, that is, the first hard disk,
the string @samp{msdos} indicates the partition scheme, while
the second integer, @samp{2}, indicates the partition number (or the
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@sc{pc} slice number in the BSD terminology). The partition numbers are
counted from @emph{one}, 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.
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@example
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(hd0,msdos5)
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@end example

This specifies the first @dfn{extended partition} of the first hard disk
drive. Note that the partition numbers for extended partitions are
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counted from @samp{5}, regardless of the actual number of primary
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partitions on your hard disk.

@example
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(hd1,msdos1,bsd1)
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@end example

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This means the BSD @samp{a} partition on first @sc{pc} slice number
of the second hard disk.
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Of course, to actually access the disks or partitions with GRUB, you
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need to use the device specification in a command, like @samp{set
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root=(fd0)} or @samp{parttool (hd0,msdos3) hidden-}. To help you find out
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which number specifies a partition you want, the GRUB command-line
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(@pxref{Command-line interface}) options have argument
completion. This means that, for example, you only need to type

@example
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set root=(
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@end example

followed by a @key{TAB}, 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.

Note that GRUB does @emph{not} 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.

Now the question is, how to specify a file? Again, consider an
example:

@example
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(hd0,msdos1)/vmlinuz
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@end example

This specifies the file named @samp{vmlinuz}, found on the first
partition of the first hard disk drive. Note that the argument
completion works with file names, too.

That was easy, admit it. Now read the next chapter, to find out how to
actually install GRUB on your drive.

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@node OS-specific notes about grub tools
@chapter OS-specific notes about grub tools

On OS which have device nodes similar to Unix-like OS GRUB tools use the
OS name. E.g. for GNU/Linux:

@example
# @kbd{grub-install /dev/sda}
@end example

On AROS we use another syntax. For volumes:

@example
//:<volume name>
@end example

E.g.

@example
//:DH0
@end example

For disks we use syntax:
@example
//:<driver name>/unit/flags
@end example

E.g.

@example
# @kbd{grub-install //:ata.device/0/0}
@end example

On Windows we use UNC path. For volumes it's typically

@example
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\\?\Volume@{<GUID>@}
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\\?\<drive letter>:
@end example

E.g.

@example
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\\?\Volume@{17f34d50-cf64-4b02-800e-51d79c3aa2ff@}
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\\?\C:
@end example


For disks it's

@example
\\?\PhysicalDrive<number>
@end example

E.g.

@example
# @kbd{grub-install \\?\PhysicalDrive0}
@end example

Beware that you may need to further escape the backslashes depending on your
shell.

When compiled with cygwin support then cygwin drive names are automatically
when needed. E.g.

@example
# @kbd{grub-install /dev/sda}
@end example
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@node Installation
@chapter Installation

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 (@pxref{Obtaining and Building GRUB}). You can do this either
from the source tarball, or as a package for your OS.

After you have done that, you need to install the boot loader on a
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drive (floppy or hard disk) by using the utility
@command{grub-install} (@pxref{Invoking grub-install}) on a UNIX-like OS.
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GRUB comes with boot images, which are normally put in the directory
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@file{/usr/lib/grub/<cpu>-<platform>} (for BIOS-based machines
@file{/usr/lib/grub/i386-pc}). Hereafter, the directory where GRUB images are
initially placed (normally @file{/usr/lib/grub/<cpu>-<platform>}) will be
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called the @dfn{image directory}, and the directory where the boot
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loader needs to find them (usually @file{/boot}) will be called
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the @dfn{boot directory}.

@menu
* Installing GRUB using grub-install::
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* Making a GRUB bootable CD-ROM::
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* Device map::
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* BIOS installation::
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@end menu


@node Installing GRUB using grub-install
@section Installing GRUB using grub-install

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For information on where GRUB should be installed on PC BIOS platforms,
@pxref{BIOS installation}.
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In order to install GRUB under a UNIX-like OS (such
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as @sc{gnu}), invoke the program @command{grub-install} (@pxref{Invoking
grub-install}) as the superuser (@dfn{root}).

The usage is basically very simple. You only need to specify one
argument to the program, namely, where to install the boot loader. The
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argument has to be either a device file (like @samp{/dev/hda}).
For example, under Linux the following will install GRUB into the MBR
of the first IDE disk:
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@example
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# @kbd{grub-install /dev/sda}
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@end example

Likewise, under GNU/Hurd, this has the same effect:

@example
# @kbd{grub-install /dev/hd0}
@end example

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But all the above examples assume that GRUB should put images under
the @file{/boot} directory. If you want GRUB to put images under a directory
other than @file{/boot}, you need to specify the option
@option{--boot-directory}. The typical usage is that you create a GRUB
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boot floppy with a filesystem. Here is an example:

@example
@group
# @kbd{mke2fs /dev/fd0}
# @kbd{mount -t ext2 /dev/fd0 /mnt}
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# @kbd{mkdir /mnt/boot}
# @kbd{grub-install --boot-directory=/mnt/boot /dev/fd0}
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# @kbd{umount /mnt}
@end group
@end example

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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
``USB-FDD'' boot). In such cases, you need to install like this:
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@example
# @kbd{losetup /dev/loop0 /dev/sdb1}
# @kbd{mount /dev/loop0 /mnt/usb}
# @kbd{grub-install --boot-directory=/mnt/usb/bugbios --force --allow-floppy /dev/loop0}
@end example

This install doesn't conflict with standard install as long as they are in
separate directories.

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Note that @command{grub-install} is actually just a shell script and the
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real task is done by other tools such as @command{grub-mkimage}. Therefore,
you may run those commands directly to install GRUB, without using
@command{grub-install}. Don't do that, however, unless you are very familiar
with the internals of GRUB. Installing a boot loader on a running OS may be
extremely dangerous.
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On EFI systems for fixed disk install you have to mount EFI System Partition.
If you mount it at @file{/boot/efi} then you don't need any special arguments:

@example
# @kbd{grub-install}
@end example

Otherwise you need to specify where your EFI System partition is mounted:

@example
# @kbd{grub-install --efi-directory=/mnt/efi}
@end example

For removable installs you have to use @option{--removable} and specify both
@option{--boot-directory} and @option{--efi-directory}:

@example
# @kbd{grub-install --efi-directory=/mnt/usb --boot-directory=/mnt/usb/boot --removable}
@end example

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@node Making a GRUB bootable CD-ROM
@section Making a GRUB bootable CD-ROM

GRUB supports the @dfn{no emulation mode} in the El Torito
specification@footnote{El Torito is a specification for bootable CD
using BIOS functions.}. This means that you can use the whole CD-ROM
from GRUB and you don't have to make a floppy or hard disk image file,
which can cause compatibility problems.

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For booting from a CD-ROM, GRUB uses a special image called
@file{cdboot.img}, which is concatenated with @file{core.img}. The
@file{core.img} used for this should be built with at least the
@samp{iso9660} and @samp{biosdisk} modules. Your bootable CD-ROM will
usually also need to include a configuration file @file{grub.cfg} and some
other GRUB modules.
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To make a simple generic GRUB rescue CD, you can use the
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@command{grub-mkrescue} program (@pxref{Invoking grub-mkrescue}):
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@example
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$ @kbd{grub-mkrescue -o grub.iso}
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@end example

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You will often need to include other files in your image. To do this, first
make a top directory for the bootable image, say, @samp{iso}:
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@example
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$ @kbd{mkdir iso}
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@end example

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Make a directory for GRUB:
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@example
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$ @kbd{mkdir -p iso/boot/grub}
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@end example

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If desired, make the config file @file{grub.cfg} under @file{iso/boot/grub}
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(@pxref{Configuration}), and copy any files and directories for the disc to the
directory @file{iso/}.

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Finally, make the image:
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@example
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$ @kbd{grub-mkrescue -o grub.iso iso}
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@end example

This produces a file named @file{grub.iso}, which then can be burned
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into a CD (or a DVD), or written to a USB mass storage device.
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The root device will be set up appropriately on entering your
@file{grub.cfg} 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.
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@node Device map
@section The map between BIOS drives and OS devices

If the device map file exists, the GRUB utilities (@command{grub-probe},
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etc.) read it to map BIOS drives to OS devices.  This file consists of lines
like this:
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@example
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(@var{device}) @var{file}
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@end example

@var{device} is a drive specified in the GRUB syntax (@pxref{Device
syntax}), and @var{file} is an OS file, which is normally a device file.

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.

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 (@file{/dev/hd*} versus @file{/dev/sd*}) may change depending
on the driver subsystem in use.  As a result, the device map file required
frequent editing on some systems.

GRUB avoids this problem nowadays by using UUIDs or file system labels when
generating @file{grub.cfg}, 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.

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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 @samp{#}.
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@node BIOS installation
@section BIOS installation

@heading MBR

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 "boot track", "MBR gap", or "embedding area", 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.

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 @file{/boot} filesystem is on the same disk that the
BIOS boots from, so that GRUB does not have to rely on guessing BIOS drive
numbers.

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.

@heading GPT

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.

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:

@example
# @kbd{parted /dev/@var{disk} set @var{partition-number} bios_grub on}
@end example

If you are using gdisk, set the partition type to @samp{0xEF02}.  With
partitioning programs that require setting the GUID directly, it should be
@samp{21686148-6449-6e6f-744e656564454649}.

@strong{Caution:} 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.


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@node Booting
@chapter Booting

GRUB can load Multiboot-compliant kernels in a consistent way,
but for some free operating systems you need to use some OS-specific
magic.

@menu
* General boot methods::        How to boot OSes with GRUB generally
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* Loopback booting::            Notes on booting from loopbacks
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* OS-specific notes::           Notes on some operating systems
@end menu


@node General boot methods
@section How to boot operating systems

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'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't support all the
existing operating systems natively.

@menu
* Loading an operating system directly::
* Chain-loading::
@end menu


@node Loading an operating system directly
@subsection How to boot an OS directly with GRUB

Multiboot (@pxref{Top, Multiboot Specification, Motivation, multiboot,
The Multiboot Specification}) 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 (@pxref{Chain-loading}).

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FIXME: this section is incomplete.
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@enumerate
@item
Run the command @command{boot} (@pxref{boot}).
@end enumerate

However, DOS and Windows have some deficiencies, so you might have to
use more complicated instructions. @xref{DOS/Windows}, for more
information.


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@node Chain-loading
@subsection Chain-loading an OS

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.

The @command{chainloader} command (@pxref{chainloader}) 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:

@verbatim
menuentry "Windows" {
	insmod chain
	insmod ntfs
	set root=(hd0,1)
	chainloader +1
}
@end verbatim
@c FIXME: document UUIDs.

On systems with multiple hard disks, an additional workaround may be
required.  @xref{DOS/Windows}.

Chain-loading is only supported on PC BIOS and EFI platforms.

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@node Loopback booting
@section Loopback booting
GRUB is able to read from an image (be it one of CD or HDD) stored on
any of its accessible storages (refer to @pxref{loopback} 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 @command{kfreebsd_module}, @command{knetbsd_module_elf},
@command{kopenbsd_ramdisk}, @command{initrd} (@pxref{initrd}),
@command{initrd16} (@pxref{initrd}), @command{multiboot_module},
@command{multiboot2_module} or @command{xnu_ramdisk}
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'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'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
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@node OS-specific notes
@section Some caveats on OS-specific issues

Here, we describe some caveats on several operating systems.

@menu
* GNU/Hurd::
* GNU/Linux::
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* NetBSD::
1002
* DOS/Windows::
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@end menu


@node GNU/Hurd
@subsection GNU/Hurd

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.

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@enumerate
1014
@item
1015
Set GRUB's root device to the same drive as GNU/Hurd's.  The command
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@code{search --set=root --file /boot/gnumach.gz} or similar may help you
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(@pxref{search}).

@item 
Load the kernel and the modules, like this:

@example
@group
grub> @kbd{multiboot /boot/gnumach.gz root=device:hd0s1}
grub> @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)' '$(task-resume)'}
grub> @kbd{module /lib/ld.so.1 exec /hurd/exec '$(exec-task=task-create)'}
@end group
@end example

@item
Finally, run the command @command{boot} (@pxref{boot}).
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@end enumerate


@node GNU/Linux
@subsection GNU/Linux

It is relatively easy to boot GNU/Linux from GRUB, because it somewhat
resembles to boot a Multiboot-compliant OS.

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@enumerate
1047
@item
1048
Set GRUB's root device to the same drive as GNU/Linux's.  The command
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@code{search --set=root --file /vmlinuz} or similar may help you
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(@pxref{search}).

@item
Load the kernel using the command @command{linux} (@pxref{linux}):

@example
grub> @kbd{linux /vmlinuz root=/dev/sda1}
@end example

If you need to specify some kernel parameters, just append them to the
command.  For example, to set @option{acpi} to @samp{off}, do this:

@example
grub> @kbd{linux /vmlinuz root=/dev/sda1 acpi=off}
@end example

See the documentation in the Linux source tree for complete information on
the available options.

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With @command{linux} GRUB uses 32-bit protocol. Some BIOS services like APM
or EDD aren't available with this protocol. In this case you need to use
@command{linux16}

@example
grub> @kbd{linux16 /vmlinuz root=/dev/sda1 acpi=off}
@end example 

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@item
If you use an initrd, execute the command @command{initrd} (@pxref{initrd})
after @command{linux}:

@example
grub> @kbd{initrd /initrd}
@end example
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If you used @command{linux16} you need to use @command{initrd16}:

@example
grub> @kbd{initrd16 /initrd}
@end example

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@item
Finally, run the command @command{boot} (@pxref{boot}).
@end enumerate

@strong{Caution:} If you use an initrd and specify the @samp{mem=}
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 @command{uppermem} @emph{before} loading the
kernel. @xref{uppermem}, for more information.


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@node NetBSD
@subsection NetBSD

Booting a NetBSD kernel from GRUB is also relatively easy: first set
GRUB's root device, then load the kernel and the modules, and finally
run @command{boot}.

@enumerate
@item
Set GRUB'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's root device as follows:

@example
grub> @kbd{insmod part_bsd}
grub> @kbd{set root=(hd0,netbsd1)}
@end example

For a disk with a GUID Partition Table (GPT), and assuming that the
NetBSD root partition is the third GPT partition, do this:

@example
grub> @kbd{insmod part_gpt}
grub> @kbd{set root=(hd0,gpt3)}
@end example

@item
Load the kernel using the command @command{knetbsd}:

@example
grub> @kbd{knetbsd /netbsd}
@end example

Various options may be given to @command{knetbsd}.  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:

@example
grub> @kbd{knetbsd /netbsd -s -v}
@end example

@item
If needed, load kernel modules with the command
@command{knetbsd_module_elf}.  A typical example is the module for the
root file system:

@example
grub> @kbd{knetbsd_module_elf /stand/amd64/6.0/modules/ffs/ffs.kmod}
@end example

@item
Finally, run the command @command{boot} (@pxref{boot}).
@end enumerate


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@node DOS/Windows
@subsection DOS/Windows

GRUB cannot boot DOS or Windows directly, so you must chain-load them
(@pxref{Chain-loading}). 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.

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 @command{drivemap} (@pxref{drivemap}), like this:

@example
drivemap -s (hd0) (hd1)
@end example

This performs a @dfn{virtual} swap between your first and second hard
drive.

@strong{Caution:} 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't work.

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.

If GRUB @dfn{hides} a DOS (or Windows) partition (@pxref{parttool}), DOS (or
Windows) will ignore the partition. If GRUB @dfn{unhides} 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:

@example
@group
parttool (hd0,1) hidden-
parttool (hd0,2) hidden+
set root=(hd0,1)
chainloader +1
parttool @verb{'${root}'} boot+
boot
@end group
@end example


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@node Configuration
@chapter Writing your own configuration file

GRUB is configured using @file{grub.cfg}, usually located under
@file{/boot/grub}.  This file is quite flexible, but most users will not
need to write the whole thing by hand.

@menu
* Simple configuration::        Recommended for most users
* Shell-like scripting::        For power users and developers
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* Multi-boot manual config::    For non-standard multi-OS scenarios
1219
* Embedded configuration::      Embedding a configuration file into GRUB
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@end menu


@node Simple configuration
@section Simple configuration handling

The program @command{grub-mkconfig} (@pxref{Invoking grub-mkconfig})
generates @file{grub.cfg} 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.

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@command{grub-mkconfig} does have some limitations.  While adding extra
custom menu entries to the end of the list can be done by editing
@file{/etc/grub.d/40_custom} or creating @file{/boot/grub/custom.cfg},
changing the order of menu entries or changing their titles may require
making complex changes to shell scripts stored in @file{/etc/grub.d/}.  This
may be improved in the future.  In the meantime, those who feel that it
would be easier to write @file{grub.cfg} directly are encouraged to do so
(@pxref{Booting}, and @ref{Shell-like scripting}), and to disable any system
provided by their distribution to automatically run @command{grub-mkconfig}.

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The file @file{/etc/default/grub} controls the operation of
@command{grub-mkconfig}.  It is sourced by a shell script, and so must be
valid POSIX shell input; normally, it will just be a sequence of
@samp{KEY=value} lines, but if the value contains spaces or other special
characters then it must be quoted.  For example:

@example
GRUB_TERMINAL_INPUT="console serial"
@end example

Valid keys in @file{/etc/default/grub} are as follows:

@table @samp
@item GRUB_DEFAULT
The default menu entry.  This may be a number, in which case it identifies
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the Nth entry in the generated menu counted from zero, or the title of a
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menu entry, or the special string @samp{saved}.  Using the id may be
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useful if you want to set a menu entry as the default even though there may
be a variable number of entries before it.

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For example, if you have:

@verbatim
1264
menuentry 'Example GNU/Linux distribution' --class gnu-linux --id example-gnu-linux {
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	...
}
@end verbatim

then you can make this the default using:

@example
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GRUB_DEFAULT=example-gnu-linux
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@end example

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Previously it was documented the way to use entry title. While this still
works it's not recommended since titles often contain unstable device names
and may be translated

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If you set this to @samp{saved}, then the default menu entry will be that
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saved by @samp{GRUB_SAVEDEFAULT} or @command{grub-set-default}.  This relies on
the environment block, which may not be available in all situations
(@pxref{Environment block}).
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The default is @samp{0}.

@item GRUB_SAVEDEFAULT
If this option is set to @samp{true}, 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 @samp{GRUB_DEFAULT=saved}; it is a separate option because
@samp{GRUB_DEFAULT=saved} is useful without this option, in conjunction with
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@command{grub-set-default}.  Unset by default.
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This option relies on the environment block, which may not be available in
all situations (@pxref{Environment block}).
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@item GRUB_TIMEOUT
Boot the default entry this many seconds after the menu is displayed, unless
a key is pressed.  The default is @samp{5}.  Set to @samp{0} to boot
immediately without displaying the menu, or to @samp{-1} to wait
indefinitely.

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If @samp{GRUB_TIMEOUT_STYLE} is set to @samp{countdown} or @samp{hidden},
the timeout is instead counted before the menu is displayed.

@item GRUB_TIMEOUT_STYLE
If this option is unset or set to @samp{menu}, then GRUB will display the
menu and then wait for the timeout set by @samp{GRUB_TIMEOUT} to expire
before booting the default entry.  Pressing a key interrupts the timeout.

If this option is set to @samp{countdown} or @samp{hidden}, then, before
displaying the menu, GRUB will wait for the timeout set by
@samp{GRUB_TIMEOUT} to expire.  If @key{ESC} is pressed during that time, it
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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 @samp{countdown} case, it will show a one-line
indication of the remaining time.
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@item GRUB_DEFAULT_BUTTON
@itemx GRUB_TIMEOUT_BUTTON
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@itemx GRUB_TIMEOUT_STYLE_BUTTON
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@itemx GRUB_BUTTON_CMOS_ADDRESS
Variants of the corresponding variables without the @samp{_BUTTON} suffix,
used to support vendor-specific power buttons.  @xref{Vendor power-on keys}.

@item GRUB_DISTRIBUTOR
Set by distributors of GRUB to their identifying name.  This is used to
generate more informative menu entry titles.

@item GRUB_TERMINAL_INPUT
Select the terminal input device.  You may select multiple devices here,
separated by spaces.

Valid terminal input names depend on the platform, but may include
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@samp{console} (native platform console), @samp{serial} (serial terminal),
@samp{serial_<port>} (serial terminal with explicit port selection),
@samp{at_keyboard} (PC AT keyboard), or @samp{usb_keyboard} (USB keyboard
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using the HID Boot Protocol, for cases where the firmware does not handle
this).

The default is to use the platform's native terminal input.

@item GRUB_TERMINAL_OUTPUT
Select the terminal output device.  You may select multiple devices here,
separated by spaces.

Valid terminal output names depend on the platform, but may include
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@samp{console} (native platform console), @samp{serial} (serial terminal),
@samp{serial_<port>} (serial terminal with explicit port selection),
@samp{gfxterm} (graphics-mode output), @samp{vga_text} (VGA text output),
@samp{mda_text} (MDA text output), @samp{morse} (Morse-coding using system
beeper) or @samp{spkmodem} (simple data protocol using system speaker).

@samp{spkmodem} is useful when no serial port is available. Connect the output
of sending system (where GRUB is running) to line-in of receiving system
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(usually developer machine).
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On receiving system compile @samp{spkmodem-recv} from
@samp{util/spkmodem-recv.c} and run:

@example
parecord --channels=1 --rate=48000 --format=s16le | ./spkmodem-recv
@end example
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The default is to use the platform's native terminal output.
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@item GRUB_TERMINAL
If this option is set, it overrides both @samp{GRUB_TERMINAL_INPUT} and
@samp{GRUB_TERMINAL_OUTPUT} to the same value.

@item GRUB_SERIAL_COMMAND
A command to configure the serial port when using the serial console.
@xref{serial}.  Defaults to @samp{serial}.

@item GRUB_CMDLINE_LINUX
Command-line arguments to add to menu entries for the Linux kernel.

@item GRUB_CMDLINE_LINUX_DEFAULT
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Unless @samp{GRUB_DISABLE_RECOVERY} is set to @samp{true}, two menu
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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
@samp{GRUB_CMDLINE_LINUX}.
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@item GRUB_CMDLINE_NETBSD
@itemx GRUB_CMDLINE_NETBSD_DEFAULT
As @samp{GRUB_CMDLINE_LINUX} and @samp{GRUB_CMDLINE_LINUX_DEFAULT}, but for
NetBSD.

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@item GRUB_CMDLINE_GNUMACH
As @samp{GRUB_CMDLINE_LINUX}, but for GNU Mach.

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@item GRUB_CMDLINE_XEN
@itemx GRUB_CMDLINE_XEN_DEFAULT
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The values of these options are passed to Xen hypervisor Xen menu entries,
for all respectively normal entries.
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@item GRUB_CMDLINE_LINUX_XEN_REPLACE
@item GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT
The values of these options replace the values of @samp{GRUB_CMDLINE_LINUX}
and @samp{GRUB_CMDLINE_LINUX_DEFAULT} for Linux and Xen menu entries.
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@item GRUB_DISABLE_LINUX_UUID
Normally, @command{grub-mkconfig} will generate menu entries that use
universally-unique identifiers (UUIDs) to identify the root filesystem to
the Linux kernel, using a @samp{root=UUID=...} 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 @samp{true}.

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@item GRUB_DISABLE_RECOVERY
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If this option is set to @samp{true}, disable the generation of recovery
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mode menu entries.
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@item GRUB_VIDEO_BACKEND
If graphical video support is required, either because the @samp{gfxterm}
graphical terminal is in use or because @samp{GRUB_GFXPAYLOAD_LINUX} is set,
then @command{grub-mkconfig} 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.

After @command{grub-install} has been run, the available video drivers are
listed in @file{/boot/grub/video.lst}.

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@item GRUB_GFXMODE
Set the resolution used on the @samp{gfxterm} 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
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available.  The default is @samp{auto}, which tries to select a preferred
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Colin Watson committed
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resolution.  @xref{gfxmode}.
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@item GRUB_BACKGROUND
Set a background image for use with the @samp{gfxterm} graphical terminal.
The value of this option must be a file readable by GRUB at boot time, and
it must end with @file{.png}, @file{.tga}, @file{.jpg}, or @file{.jpeg}.
The image will be scaled if necessary to fit the screen.

@item GRUB_THEME
Set a theme for use with the @samp{gfxterm} graphical terminal.

@item GRUB_GFXPAYLOAD_LINUX
Set to @samp{text} to force the Linux kernel to boot in normal text mode,
@samp{keep} to preserve the graphics mode set using @samp{GRUB_GFXMODE},
@samp{@var{width}x@var{height}}[@samp{x@var{depth}}] to set a particular
graphics mode, or a sequence of these separated by commas or semicolons to
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try several modes in sequence.  @xref{gfxpayload}.
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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
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boot sequence.  If you have problems, set this option to @samp{text} and
GRUB will tell Linux to boot in normal text mode.
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@item GRUB_DISABLE_OS_PROBER
Normally, @command{grub-mkconfig} will try to use the external
@command{os-prober} program, if installed, to discover other operating
systems installed on the same system and generate appropriate menu entries
for them.  Set this option to @samp{true} to disable this.

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@item GRUB_OS_PROBER_SKIP_LIST
List of space-separated FS UUIDs of filesystems to be ignored from os-prober
output. For efi chainloaders it's <UUID>@@<EFI FILE>

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@item GRUB_DISABLE_SUBMENU
Normally, @command{grub-mkconfig} 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 @command{os-prober} first entry will be put on top level and all others
in submenu. If this option is set to @samp{y}, flat menu with all entries
on top level will be generated instead. Changing this option will require
changing existing values of @samp{GRUB_DEFAULT}, @samp{fallback} (@pxref{fallback})
and @samp{default} (@pxref{default}) environment variables as well as saved
default entry using @command{grub-set-default} and value used with
@command{grub-reboot}.

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@item GRUB_ENABLE_CRYPTODISK
If set to @samp{y}, @command{grub-mkconfig} and @command{grub-install} 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.

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@item GRUB_INIT_TUNE
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 @ref{play}.
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@item GRUB_BADRAM
If this option is set, GRUB will issue a @ref{badram} command to filter
out specified regions of RAM.

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@item GRUB_PRELOAD_MODULES
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
@file{grub.cfg}.

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@item GRUB_RECORDFAIL_TIMEOUT
If this option is set, it overrides the default recordfail setting.  A
setting of -1 causes GRUB to wait for user input indefinitely.  However, a
false positive in the recordfail mechanism may occur if power is lost during
boot before boot success is recorded in userspace.  The default setting is
30, which causes GRUB to wait for user input for thirty seconds before
continuing.  This default allows interactive users the opportunity to switch
to a different, working kernel, while avoiding a false positive causing the
boot to block indefinitely on headless and appliance systems where access to
a console is restricted or limited.

This option is only effective when GRUB was configured with the
@option{--enable-quick-boot} option.

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@item GRUB_RECOVERY_TITLE
This option sets the English text of the string that will be displayed in
parentheses to indicate that a boot option is provided to help users recover
a broken system.  The default is "recovery mode".

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@end table

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The following options are still accepted for compatibility with existing
configurations, but have better replacements:

@table @samp
@item GRUB_HIDDEN_TIMEOUT
Wait this many seconds before displaying the menu.  If @key{ESC} is pressed
during that time, display the menu and wait for input according to
@samp{GRUB_TIMEOUT}.  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 @samp{GRUB_TIMEOUT} before booting the default entry.

If you set @samp{GRUB_HIDDEN_TIMEOUT}, you should also set
@samp{GRUB_TIMEOUT=0} so that the menu is not displayed at all unless
@key{ESC} is pressed.

This option is unset by default, and is deprecated in favour of the less
confusing @samp{GRUB_TIMEOUT_STYLE=countdown} or
@samp{GRUB_TIMEOUT_STYLE=hidden}.

@item GRUB_HIDDEN_TIMEOUT_QUIET
In conjunction with @samp{GRUB_HIDDEN_TIMEOUT}, set this to @samp{true} to
suppress the verbose countdown while waiting for a key to be pressed before
displaying the menu.

This option is unset by default, and is deprecated in favour of the less
confusing @samp{GRUB_TIMEOUT_STYLE=countdown}.

@item GRUB_HIDDEN_TIMEOUT_BUTTON
Variant of @samp{GRUB_HIDDEN_TIMEOUT}, used to support vendor-specific power
buttons.  @xref{Vendor power-on keys}.

This option is unset by default, and is deprecated in favour of the less
confusing @samp{GRUB_TIMEOUT_STYLE=countdown} or
@samp{GRUB_TIMEOUT_STYLE=hidden}.

@end table

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For more detailed customisation of @command{grub-mkconfig}'s output, you may
edit the scripts in @file{/etc/grub.d} directly.
@file{/etc/grub.d/40_custom} 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.


@node Shell-like scripting
@section Writing full configuration files directly

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@c Some of this section is derived from the GNU Bash manual page, also
@c copyrighted by the FSF.

@file{grub.cfg} is written in GRUB's built-in scripting language, which has
a syntax quite similar to that of GNU Bash and other Bourne shell
derivatives.

@heading Words

A @dfn{word} is a sequence of characters considered as a single unit by
GRUB.  Words are separated by @dfn{metacharacters}, which are the following
plus space, tab, and newline:

@example
@{ @} | & $ ; < >
@end example
 
Quoting may be used to include metacharacters in words; see below.

@heading Reserved words

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} command:

@example
! [[ ]] @{ @}
case do done elif else esac fi for function
if in menuentry select then time until while
@end example

Not all of these reserved words have a useful purpose yet; some are reserved
for future expansion.

@heading Quoting

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.

There are three quoting mechanisms: the escape character, single quotes, and
double quotes.

A non-quoted backslash (\) is the @dfn{escape character}.  It preserves the
literal value of the next character that follows, with the exception of
newline.

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.

Enclosing characters in double quotes preserves the literal value of all
characters within the quotes, with the exception of @samp{$} and @samp{\}.
The @samp{$} character retains its special meaning within double quotes.
The backslash retains its special meaning only when followed by one of the
following characters: @samp{$}, @samp{"}, @samp{\}, or newline.  A
backslash-newline pair is treated as a line continuation (that is, it is
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removed from the input stream and effectively ignored@footnote{Currently a
backslash-newline pair within a variable name is not handled properly, so
use this feature with some care.}).  A double quote may be quoted within
double quotes by preceding it with a backslash.
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@heading Variable expansion

The @samp{$} 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.

Normal variable names begin with an alphabetic character, followed by zero
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or more alphanumeric characters.  These names refer to entries in the GRUB
environment (@pxref{Environment}).
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Positional variable names consist of one or more digits.  They represent
parameters passed to function calls, with @samp{$1} representing the first
parameter, and so on.
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The special variable name @samp{?} expands to the exit status of the most
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recently executed command.  When positional variable names are active, other
special variable names @samp{@@}, @samp{*} and @samp{#} are defined and they
expand to all positional parameters with necessary quoting, positional
parameters without any quoting, and positional parameter count respectively.
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@heading Comments

A word beginning with @samp{#} causes that word and all remaining characters
on that line to be ignored.

@heading Simple commands

A @dfn{simple command} 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.

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The return value of a simple command is its exit status.  If the reserved
word @code{!} precedes the command, then the return value is instead the
logical negation of the command's exit status.
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@heading Compound commands

A @dfn{compound command} is one of the following:

@table @asis
@item for @var{name} in @var{word} @dots{}; do @var{list}; done
The list of words following @code{in} is expanded, generating a list of
items.  The variable @var{name} is set to each element of this list in turn,
and @var{list} 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} results in an empty list, no commands are executed, and the return
status is 0.

@item if @var{list}; then @var{list}; [elif @var{list}; then @var{list};] @dots{} [else @var{list};] fi
The @code{if} @var{list} is executed.  If its exit status is zero, the
@code{then} @var{list} is executed.  Otherwise, each @code{elif} @var{list}
is executed in turn, and if its exit status is zero, the corresponding
@code{then} @var{list} is executed and the command completes.  Otherwise,
the @code{else} @var{list} is executed, if present.  The exit status is the
exit status of the last command executed, or zero if no condition tested
true.

@item while @var{cond}; do @var{list}; done
@itemx until @var{cond}; do @var{list}; done
The @code{while} command continuously executes the @code{do} @var{list} as
long as the last command in @var{cond} returns an exit status of zero.  The
@code{until} command is identical to the @code{while} command, except that
the test is negated; the @code{do} @var{list} is executed as long as the
last command in @var{cond} returns a non-zero exit status.  The exit status
of the @code{while} and @code{until} commands is the exit status of the last
@code{do} @var{list} command executed, or zero if none was executed.

@item function @var{name} @{ @var{command}; @dots{} @}
This defines a function named @var{name}.  The @dfn{body} 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} is specified as the name of a simple command.  Function
definitions do not affect the exit status in @code{$?}.  When executed, the
exit status of a function is the exit status of the last command executed in
the body.

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@item menuentry @var{title} [@option{--class=class} @dots{}] [@option{--users=users}] [@option{--unrestricted}] [@option{--hotkey=key}] [@option{--id=id}] @{ @var{command}; @dots{} @}
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@xref{menuentry}.
@end table

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@heading Built-in Commands

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.

@table @asis
@item break [@code{n}]
Exit from within a @code{for}, @code{while}, or @code{until} loop.  If
@code{n} is specified, break @code{n} levels.  @code{n} must be greater than
or equal to 1.  If @code{n} is greater than the number of enclosing loops,
all enclosing loops are exited.  The return value is 0 unless @code{n} is
not greater than or equal to 1.

@item continue [@code{n}]
Resume the next iteration of the enclosing @code{for}, @code{while} or
@code{until} loop.  If @code{n} is specified, resume at the @code{n}th
enclosing loop.  @code{n} must be greater than or equal to 1.  If @code{n}
is greater than the number of enclosing loops, the last enclosing loop (the
@dfn{top-level} loop) is resumed.  The return value is 0 unless @code{n} is
not greater than or equal to 1.

@item return [@code{n}]
Causes a function to exit with the return value specified by @code{n}.  If
@code{n} 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.

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@item setparams [@code{arg}] @dots{}
Replace positional parameters starting with @code{$1} with arguments to
@command{setparams}.

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@item shift [@code{n}]
The positional parameters from @code{n}+1 @dots{} are renamed to
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@code{$1}@dots{}.  Parameters represented by the numbers @code{$#} down to
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@code{$#}-@code{n}+1 are unset.  @code{n} must be a non-negative number less
than or equal to @code{$#}.  If @code{n} is 0, no parameters are changed.
If @code{n} is not given, it is assumed to be 1.  If @code{n} is greater
than @code{$#}, the positional parameters are not changed.  The return
status is greater than zero if @code{n} is greater than @code{$#} or less
than zero; otherwise 0.

@end table
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@node Multi-boot manual config
@section Multi-boot manual config

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.

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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:
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@code{grub-install --boot-directory=/mnt/boot /dev/sda}

In all the OSes install GRUB tools but disable installing GRUB in bootsector,
so you'll have menu.lst and grub.cfg available for use. Also disable os-prober
use by setting:

@code{GRUB_DISABLE_OS_PROBER=true}

in /etc/default/grub

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Then write a grub.cfg (/mnt/boot/grub/grub.cfg):
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@example

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

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

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

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

menuentry "FreeBSD" @{
          insmod zfs
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          search --set=root --label freepool --hint hd0,msdos7
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          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 "experimental GRUB" @{
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          search --set=root --label GRUB --hint hd0,msdos5
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          multiboot /experimental/grub/i386-pc/core.img
@}

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

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menuentry "Fedora rawhide installer" @{
          search --set=root --label GRUB --hint hd0,msdos5
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          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
@}

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menuentry "Debian sid installer" @{
          search --set=root --label GRUB --hint hd0,msdos5
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          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
@}

@end example

Notes:
@itemize
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@item Argument to search after --label is FS LABEL. You can also use UUIDs with --fs-uuid UUID instead of --label LABEL. You could also use direct @code{root=hd0,msdosX} but this is not recommended due to device name instability.
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@end itemize

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@node Embedded configuration
@section Embedding a configuration file into GRUB

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.
@command{grub-install} uses this feature when it is not using BIOS disk
functions or when installing to a different disk from the one containing
@file{/boot/grub}, in which case it needs to use the @command{search}
command (@pxref{search}) to find @file{/boot/grub}.

To embed a configuration file, use the @option{-c} option to
@command{grub-mkimage}.  The file is copied into the core image, so it may
reside anywhere on the file system, and may be removed after running
@command{grub-mkimage}.

After the embedded configuration file (if any) is executed, GRUB will load
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the @samp{normal} module (@pxref{normal}), which will then read the real
configuration file from @file{$prefix/grub.cfg}.  By this point, the
@code{root} variable will also have been set to the root device name.  For
example, @code{prefix} might be set to @samp{(hd0,1)/boot/grub}, and
@code{root} might be set to @samp{hd0,1}.  Thus, in most cases, the embedded
configuration file only needs to set the @code{prefix} and @code{root}
variables, and then drop through to GRUB's normal processing.  A typical
example of this might look like this:
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@example
@group
search.fs_uuid 01234567-89ab-cdef-0123-456789abcdef root
set prefix=($root)/boot/grub
@end group
@end example

(The @samp{search_fs_uuid} module must be included in the core image for this
example to work.)

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 @file{grub.cfg}, or reading files from a directory
other than that where GRUB's loadable modules are installed.  To do this,
include the @samp{configfile} and @samp{normal} modules in the core image,
and embed a configuration file that uses the @command{configfile} command to
load another file.  The following example of this also requires the
@command{echo}, @command{search_label}, and @command{test} modules to be
included in the core image:

@example
@group
search.fs_label grub root
if [ -e /boot/grub/example/test1.cfg ]; then
    set prefix=($root)/boot/grub
    configfile /boot/grub/example/test1.cfg
else
    if [ -e /boot/grub/example/test2.cfg ]; then
        set prefix=($root)/boot/grub
        configfile /boot/grub/example/test2.cfg
    else
        echo "Could not find an example configuration file!"
    fi
fi
@end group
@end example

The embedded configuration file may not contain menu entries directly, but
may only read them from elsewhere using @command{configfile}.

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@node Theme file format
@chapter Theme file format
@section Introduction
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

@section Theme Elements
@subsection Colors

Colors can be specified in several ways:

@itemize
@item HTML-style ``#RRGGBB'' or ``#RGB'' format, where *R*, *G*, and *B* are hexadecimal digits (e.g., ``#8899FF'')
@item as comma-separated decimal RGB values (e.g., ``128, 128, 255'')
@item with ``SVG 1.0 color names'' (e.g., ``cornflowerblue'') which must be specified in lowercase.
@end itemize
@subsection Fonts
The fonts GRUB uses ``PFF2 font format'' 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.
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Fonts are loaded with the ``loadfont'' command in GRUB (@ref{loadfont}).  To see the list of
loaded fonts, execute the ``lsfonts'' command (@ref{lsfonts}).  If there are too many fonts to
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fit on screen, do ``set pager=1'' before executing ``lsfonts''.


@subsection Progress Bar

@float Figure, Pixmap-styled progress bar
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@c @image{Theme_progress_bar,,,,png}
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@end float

@float Figure, Plain progress bar, drawn with solid color.
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@c @image{Theme_progress_bar_filled,,,,png}
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@end float

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 ``progress_bar'' component with
the id ``__timeout__''.  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.

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Progress bars may optionally have text displayed on them.  This text is
controlled by variable ``text'' which contains a printf template with the
only argument %d is the number of seconds remaining. Additionally special
values ``@@TIMEOUT_NOTIFICATION_SHORT@@'', ``@@TIMEOUT_NOTIFICATION_MIDDLE@@'',
``@@TIMEOUT_NOTIFICATION_LONG@@'' are replaced with standard and translated
templates.
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@subsection Circular Progress Indicator

@c @image{Theme_circular_progress,,,,.png}

The circular progress indicator functions similarly to the progress bar.  When
given an id of ``__timeout__'', GRUB updates the circular progress indicator'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.


@subsection Labels

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
``__timeout__'', then the ``text'' 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.


@subsection Boot Menu

@c @image{Theme_boot_menu,,,,.png}

The boot menu where GRUB displays the menu entries from the ``grub.cfg'' 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 ``myclass.png'' in the ``grub/themes/icons''
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.


@subsection Styled Boxes

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:

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@multitable @columnfractions 0.3 0.3 0.3
@item Northwest (nw) @tab North (n)  @tab Northeast (ne)
@item West (w)       @tab Center (c) @tab East (e)
@item Southwest (sw) @tab South (s)  @tab Southeast (se)
@end multitable
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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:

@enumerate
@item 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.
@item The corner slices (northwest, northeast, southeast, and southwest) are not scaled.
@item The center slice is scaled to fill the remaining space in the middle.
@end enumerate

As an example of how an image might be sliced up, consider the styled box
used for a terminal view.

@float Figure, An example of the slices (in red) used for a terminal window. This drawing was created and sliced in Inkscape_, as the next section explains.
@c @image{Box_slice_example_terminal,,,,.png}
@end float
   
@subsection Creating Styled Box Images

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:

@enumerate
@item Create or open the drawing you'd like use.
@item Create a new layer on the top of the layer stack.  Make it visible.  Select this layer as the current layer.
@item Draw 9 rectangles on your drawing where you'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.
@item Right click on the center slice rectangle and choose Object Properties. Change the "Id" to ``slice_c`` and click Set.  Repeat this for the remaining 8 rectangles, giving them Id values of ``slice_n``, ``slice_ne``, ``slice_e``, and so on according to the location.
@item Save the drawing.
@item 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.
@item Click the layer hide icon for the slice layer in the layer palette.  The rectangles will remain selected, even though they are hidden.
@item 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.
@end enumerate

@section Theme File Manual

The theme file is a plain text file.  Lines that begin with ``#`` are ignored
and considered comments.  (Note: This may not be the case if the previous line
ended where a value was expected.)

The theme file contains two types of statements:
@enumerate
@item Global properties.
@item Component construction.
@end enumerate

@subsection Global Properties

@subsection Format

Global properties are specified with the simple format:
@itemize
@item name1: value1
@item name2: "value which may contain spaces"
@item name3: #88F
@end itemize

In this example, name3 is assigned a color value.


@subsection Global Property List

@multitable @columnfractions 0.3 0.6
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@item title-text
   @tab Specifies the text to display at the top center of the screen as a title.
@item title-font
   @tab Defines the font used for the title message at the top of the screen.
@item title-color
   @tab Defines the color of the title message.
@item message-font
   @tab Currently unused. Left for backward compatibility.
@item message-color
   @tab Currently unused. Left for backward compatibility.
@item message-bg-color
   @tab Currently unused. Left for backward compatibility.
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@item desktop-image
   @tab 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.
@item desktop-image-scale-method
   @tab Specifies the scaling method for the *desktop-image*. Options are
   ``stretch``, ``crop``, ``padding``, ``fitwidth``, ``fitheight``.
   ``stretch`` for fitting the screen size. Otherwise it is proportional
   scaling of a part of *desktop-image* to the part of the screen.
   ``crop`` part of the *desktop-image* will be proportionally scaled to
   fit the screen sizes. ``padding`` the entire *desktop-image* will be
   contained on the screen. ``fitwidth`` for fitting the *desktop-image*'s
   width with screen width. ``fitheight`` for fitting the *desktop-image*'s
   height with the screen height. Default is ``stretch``.
@item desktop-image-h-align
   @tab Specifies the horizontal alignment of the *desktop-image* if
   *desktop-image-scale-method* isn't equeal to ``stretch``. Options are
   ``left``, ``center``, ``right``. Default is ``center``.
@item desktop-image-v-align
   @tab Specifies the vertical alignment of the *desktop-image* if
   *desktop-image-scale-method* isn't equeal to ``stretch``. Options are
   ``top``, ``center``, ``bottom``. Default is ``center``.
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@item desktop-color
   @tab Specifies the color for the background if *desktop-image* is not
   specified.
@item terminal-box
   @tab Specifies the file name pattern for the styled box slices used for the
   command line terminal window.  For example, ``terminal-box: terminal_*.png``
   will use the images ``terminal_c.png`` as the center area, ``terminal_n.png``
   as the north (top) edge, ``terminal_nw.png`` as the northwest (upper left)
   corner, and so on.  If the image for any slice is not found, it will simply
   be left empty.
@item terminal-border
   @tab Specifies the border width of the terminal window.
@item terminal-left
   @tab Specifies the left coordinate of the terminal window.
@item terminal-top
   @tab Specifies the top coordinate of the terminal window.
@item terminal-width
   @tab Specifies the width of the terminal window.
@item terminal-height
   @tab Specifies the height of the terminal window.
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@end multitable


@subsection Component Construction

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.

Components are created in the theme file by prefixing the type of component
with a '+' sign:

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@code{   + label @{ text="GRUB" font="aqui 11" color="#8FF" @} }
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properties of a component are specified as "name = value" (whitespace
surrounding tokens is optional and is ignored) where *value* may be:
@itemize
@item a single word (e.g., ``align = center``, ``color = #FF8080``),
@item a quoted string (e.g., ``text = "Hello, World!"``), or
@item a tuple (e.g., ``preferred_size = (120, 80)``).
@end itemize

@subsection Component List

The following is a list of the components and the properties they support.

@itemize
@item label
   A label displays a line of text.
   
   Properties:
   @multitable @columnfractions 0.2 0.7
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   @item id
      @tab Set to ``__timeout__`` to display the time elapsed to an automatical
      boot of the default entry.
   @item text
      @tab The text to display. If ``id`` is set to ``__timeout__`` and no
      ``text`` property is set then the amount of seconds will be shown.
      If set to ``@@KEYMAP_SHORT@@``, ``@@KEYMAP_MIDDLE@@`` or
      ``@@KEYMAP_LONG@@`` then predefined hotkey information will be shown.
   @item font
      @tab The font to use for text display.
   @item color
      @tab The color of the text.
   @item align
      @tab The horizontal alignment of the text within the component.
      Options are ``left``, ``center`` and ``right``.
   @item visible
      @tab Set to ``false`` to hide the label.
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   @end multitable

@item image
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   A component that displays an image.  The image is scaled to fit
   the component.
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   Properties:

   @multitable @columnfractions 0.2 0.7
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   @item file
      @tab The full path to the image file to load.
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   @end multitable

@item 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.

   Properties:

   @multitable @columnfractions 0.2 0.7
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   @item id
      @tab Set to ``__timeout__`` to display the time elapsed to an automatical
      boot of the default entry.
   @item fg_color
      @tab The foreground color for plain solid color rendering.
   @item bg_color
      @tab The background color for plain solid color rendering.
   @item border_color
      @tab The border color for plain solid color rendering.
   @item text_color
      @tab The text color.
   @item bar_style
      @tab The styled box specification for the frame of the progress bar.
      Example: ``progress_frame_*.png``
      If the value is equal to ``highlight_style`` then no styled boxes
      will be shown.
   @item highlight_style
      @tab 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: ``progress_hl_*.png``.
      If the value is equal to ``bar_style`` then no styled boxes
      will be shown.
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   @item highlight_overlay
      @tab If this option is set to ``true`` 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't be a free space from the highlight to
      the frame in top and bottom scrollbar positions. Default is ``false``.
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   @item font
      @tab The font to use for progress bar.
   @item text
      @tab The text to display on the progress bar.  If the progress bar's ID
      is set to ``__timeout__`` and the value of this property is set to
      ``@@TIMEOUT_NOTIFICATION_SHORT@@``, ``@@TIMEOUT_NOTIFICATION_MIDDLE@@``
      or ``@@TIMEOUT_NOTIFICATION_LONG@@``, then GRUB will update this
      property with an informative message as the timeout approaches.
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   @end multitable

@item 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.

   Properties:

   @multitable @columnfractions 0.3 0.6
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   @item id
      @tab Set to ``__timeout__`` to display the time elapsed to an automatical
      boot of the default entry.
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   @item center_bitmap
      @tab The file name of the image to draw in the center of the component.
   @item tick_bitmap
      @tab The file name of the image to draw for the tick marks.
   @item num_ticks
      @tab The number of ticks that make up a full circle.
   @item ticks_disappear
      @tab Boolean value indicating whether tick marks should progressively appear,
      or progressively disappear as *value* approaches *end*.  Specify
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      ``true`` or ``false``. Default is ``false``.
   @item start_angle
      @tab The position of the first tick mark to appear or disappear.
      Measured in "parrots", 1 "parrot" = 1 / 256 of the full circle.
      Use values ``xxx deg`` or ``xxx \xc2\xb0`` to set the angle in degrees.
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   @end multitable
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