path: root/system/grub2/grub.info

This is docs/grub.info, produced by makeinfo version 4.13 from
docs/grub.texi.

This manual is for GNU GRUB (version 1.98, 2 June 2010).

   Copyright (C) 1999,2000,2001,2002,2004,2006,2008,2009,2010 Free
Software Foundation, Inc.

     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.

INFO-DIR-SECTION Kernel
START-INFO-DIR-ENTRY
* GRUB: (grub).                 The GRand Unified Bootloader
* grub-install: (grub)Invoking grub-install.    Install GRUB on your drive
* grub-mkconfig: (grub)Invoking grub-mkconfig.  Generate GRUB configuration
END-INFO-DIR-ENTRY


File: grub.info,  Node: Top,  Next: Introduction,  Up: (dir)

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 1.98.

   This manual is for GNU GRUB (version 1.98, 2 June 2010).

   Copyright (C) 1999,2000,2001,2002,2004,2006,2008,2009,2010 Free
Software Foundation, Inc.

     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.

* Menu:

* Introduction::                Capturing the spirit of GRUB
* Naming convention::           Names of your drives in GRUB
* Installation::                Installing GRUB on your drive
* Booting::                     How to boot different operating systems
* Configuration::               Writing your own configuration file
* Network::                     Downloading OS images from a network
* Serial terminal::             Using GRUB via a serial line
* Vendor power-on keys::        Changing GRUB behaviour on vendor power-on keys
* Preset Menu::                 Embedding a configuration file into GRUB
* Images::                      GRUB image files
* Filesystem::                  Filesystem syntax and semantics
* Interface::                   The menu and the command-line
* Commands::                    The list of available builtin commands
* Troubleshooting::             Error messages produced by GRUB
* Invoking grub-install::       How to use the GRUB installer
* Invoking grub-mkconfig::      Generate a GRUB configuration file
* 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
* Internals::                   Hacking GRUB
* Copying This Manual::         Copying This Manual
* Index::


File: grub.info,  Node: Introduction,  Next: Naming convention,  Prev: Top,  Up: Top

1 Introduction to GRUB
**********************

* Menu:

* Overview::                    What exactly GRUB is and how to use it
* History::                     From maggot to house fly
* Features::                    GRUB features
* Role of a boot loader::       The role of a boot loader


File: grub.info,  Node: Overview,  Next: History,  Up: Introduction

1.1 Overview
============

Briefly, a "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 "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(1) (*note Overview-Footnote-1::). 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
(*note Command-line interface::), or a menu interface (*note 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 (*note
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 (*note Naming convention::) to GRUB, how to
install GRUB on your drive (*note Installation::), and how to boot your
OSes (*note Booting::), step by step.


File: grub.info,  Node: Overview-Footnotes,  Up: Overview

   (1) "chain-load" is the mechanism for loading unsupported operating
systems by loading another boot loader. It is typically used for
loading DOS or Windows.


File: grub.info,  Node: History,  Next: Features,  Prev: Overview,  Up: Introduction

1.2 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
(*note Multiboot Specification: (multiboot)Top.), 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. *Note Obtaining and Building
GRUB::, for more information.


File: grub.info,  Node: Features,  Next: Role of a boot loader,  Prev: History,  Up: Introduction

1.3 GRUB features
=================

The primary requirement for GRUB is that it be compliant with the
"Multiboot Specification", which is described in *note Multiboot
Specification: (multiboot)Top.

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

   * Basic functions must be straightforward for end-users.

   * Rich functionality to support kernel experts and designers.

   * 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.

   Except for specific compatibility modes (chain-loading and the Linux
"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):

Recognize multiple executable formats
     Support many of the "a.out" variants plus "ELF". Symbol tables are
     also loaded.

Support non-Multiboot kernels
     Support many of the various free 32-bit kernels that lack Multiboot
     compliance (primarily FreeBSD, NetBSD, OpenBSD, and Linux).
     Chain-loading of other boot loaders is also supported.

Load multiples modules
     Fully support the Multiboot feature of loading multiple modules.

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 (*note Commands::) are a superset of those
     supported on the command-line. An example configuration file is
     provided in *note Configuration::.

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.

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 (*note Commands::) are a subset of those
     supported for configuration files. Editing commands closely
     resembles the Bash command-line (*note Bash: (features)Command
     Line Editing.), with <TAB>-completion of commands, devices,
     partitions, and files in a directory depending on context.

Support multiple filesystem types
     Support multiple filesystem types transparently, plus a useful
     explicit blocklist notation. The currently supported filesystem
     types are "BSD FFS", "DOS FAT16 and FAT32", "Minix fs", "Linux
     ext2fs", "ReiserFS", "JFS", "XFS", and "VSTa fs". *Note
     Filesystem::, for more information.

Support automatic decompression
     Can decompress files which were compressed by `gzip'. This
     function is both automatic and transparent to the user (i.e. all
     functions operate upon the uncompressed contents of the specified
     files). This greatly reduces a file size and loading time, a
     particularly great benefit for floppies.(1) (*note
     Features-Footnote-1::)

     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.

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.

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.

Detect all installed RAM
     GRUB can generally find all the installed RAM on a PC-compatible
     machine. It uses an advanced BIOS query technique for finding all
     memory regions. As described on the Multiboot Specification (*note
     Multiboot Specification: (multiboot)Top.), not all kernels make
     use of this information, but GRUB provides it for those who do.

Support Logical Block Address mode
     In traditional disk calls (called "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 ("LBA") mode. GRUB automatically detects if LBA mode is
     available and uses it if available. In LBA mode, GRUB can access
     the entire disk.

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 "TFTP"
     protocol.

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.


File: grub.info,  Node: Features-Footnotes,  Up: Features

   (1) There are a few pathological cases where loading a very badly
organized ELF kernel might take longer, but in practice this never
happen.


File: grub.info,  Node: Role of a boot loader,  Prev: Features,  Up: Introduction

1.4 The role of a boot loader
=============================

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

     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
     _boot loader_ is the most important software of all. I used to
     refer to the above systems as either "LILO"(1) (*note Role of a
     boot loader-Footnote-1::) 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... GRUB!

   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.


File: grub.info,  Node: Role of a boot loader-Footnotes,  Up: Role of a boot loader

   (1) The LInux LOader, a boot loader that everybody uses, but nobody
likes.


File: grub.info,  Node: Naming convention,  Next: Installation,  Prev: Introduction,  Up: Top

2 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:

     (fd0)

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

     (hd0,2)

   Here, `hd' means it is a hard disk drive. The first integer `0'
indicates the drive number, that is, the first hard disk, while the
second integer, `1', indicates the partition number (or the PC slice
number in the BSD terminology). The partition numbers are counted from
_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.

     (hd0,5)

   This specifies the first "extended partition" of the first hard disk
drive. Note that the partition numbers for extended partitions are
counted from `5', regardless of the actual number of primary partitions
on your hard disk.

     (hd1,a)

   This means the BSD `a' partition of the second hard disk. If you
need to specify which PC slice number should be used, use something
like this: `(hd1,1,a)'. If the PC slice number is omitted, GRUB
searches for the first PC slice which has a BSD `a' partition.

   Of course, to actually access the disks or partitions with GRUB, you
need to use the device specification in a command, like `root (fd0)' or
`unhide (hd0,3)'. To help you find out which number specifies a
partition you want, the GRUB command-line (*note Command-line
interface::) options have argument completion. This means that, for
example, you only need to type

     root (

   followed by a <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 _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:

     (hd0,1)/vmlinuz

   This specifies the file named `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.


File: grub.info,  Node: Installation,  Next: Booting,  Prev: Naming convention,  Up: Top

3 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
(*note 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
drive (floppy or hard disk). There are two ways of doing that - either
using the utility `grub-install' (*note Invoking grub-install::) on a
UNIX-like OS, or by running GRUB itself from a floppy. These are quite
similar, however the utility might probe a wrong BIOS drive, so you
should be careful.

   Also, if you install GRUB on a UNIX-like OS, please make sure that
you have an emergency boot disk ready, so that you can rescue your
computer if, by any chance, your hard drive becomes unusable
(unbootable).

   GRUB comes with boot images, which are normally put in the directory
`/usr/lib/grub/i386-pc'. Hereafter, the directory where GRUB images are
initially placed (normally `/usr/lib/grub/i386-pc') will be called the
"image directory", and the directory where the boot loader needs to
find them (usually `/boot/grub') will be called the "boot directory".

* Menu:

* Installing GRUB using grub-install::
* Making a GRUB bootable CD-ROM::


File: grub.info,  Node: Installing GRUB using grub-install,  Next: Making a GRUB bootable CD-ROM,  Up: Installation

3.1 Installing GRUB using grub-install
======================================

*Caution:* This procedure is definitely less safe, because there are
several ways in which your computer can become unbootable. For example,
most operating systems don't tell GRUB how to map BIOS drives to OS
devices correctly--GRUB merely "guesses" the mapping. This will succeed
in most cases, but not always. Therefore, GRUB provides you with a map
file called the "device map", which you must fix if it is wrong. *Note
Device map::, for more details.

   If you still do want to install GRUB under a UNIX-like OS (such as
GNU), invoke the program `grub-install' (*note Invoking grub-install::)
as the superuser ("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
argument can be either a device file (like `/dev/hda') or a partition
specified in GRUB's notation. For example, under Linux the following
will install GRUB into the MBR of the first IDE disk:

     # grub-install /dev/hda

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

     # grub-install /dev/hd0

   If it is the first BIOS drive, this is the same as well:

     # grub-install '(hd0)'

   Or you can omit the parentheses:

     # grub-install hd0

   But all the above examples assume that GRUB should use images under
the root directory. If you want GRUB to use images under a directory
other than the root directory, you need to specify the option
`--root-directory'. The typical usage is that you create a GRUB boot
floppy with a filesystem. Here is an example:

     # mke2fs /dev/fd0
     # mount -t ext2 /dev/fd0 /mnt
     # grub-install --root-directory=/mnt fd0
     # umount /mnt

   Another example is when you have a separate boot partition which is
mounted at `/boot'. Since GRUB is a boot loader, it doesn't know
anything about mountpoints at all. Thus, you need to run `grub-install'
like this:

     # grub-install --root-directory=/boot /dev/hda

   By the way, as noted above, it is quite difficult to guess BIOS
drives correctly under a UNIX-like OS. Thus, `grub-install' will prompt
you to check if it could really guess the correct mappings, after the
installation. The format is defined in *note Device map::. Please be
quite careful. If the output is wrong, it is unlikely that your
computer will be able to boot with no problem.

   Note that `grub-install' is actually just a shell script and the
real task is done by `grub-mkimage' and `grub-setup'.  Therefore, you
may run those commands directly to install GRUB, without using
`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.


File: grub.info,  Node: Making a GRUB bootable CD-ROM,  Prev: Installing GRUB using grub-install,  Up: Installation

3.2 Making a GRUB bootable CD-ROM
=================================

GRUB supports the "no emulation mode" in the El Torito specification(1)
(*note Making a GRUB bootable CD-ROM-Footnote-1::). 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.

   For booting from a CD-ROM, GRUB uses a special Stage 2 called
`stage2_eltorito'. The only GRUB files you need to have in your
bootable CD-ROM are this `stage2_eltorito' and optionally a config file
`grub.cfg'. You don't need to use `stage1' or `stage2', because El
Torito is quite different from the standard boot process.

   Here is an example of procedures to make a bootable CD-ROM image.
First, make a top directory for the bootable image, say, `iso':

     $ mkdir iso

   Make a directory for GRUB:

     $ mkdir -p iso/boot/grub

   Copy the file `stage2_eltorito':

     $ cp /usr/lib/grub/i386-pc/stage2_eltorito iso/boot/grub

   If desired, make the config file `grub.cfg' under `iso/boot/grub'
(*note Configuration::), and copy any files and directories for the
disc to the directory `iso/'.

   Finally, make a ISO9660 image file like this:

     $ mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot \
         -boot-load-size 4 -boot-info-table -o grub.iso iso

   This produces a file named `grub.iso', which then can be burned into
a CD (or a DVD).  `mkisofs' has already set up the disc to boot from
the `boot/grub/stage2_eltorito' file, so there is no need to setup GRUB
on the disc.  (Note that the `-boot-load-size 4' bit is required for
compatibility with the BIOS on many older machines.)

   You can use the device `(cd)' to access a CD-ROM in your config
file. This is not required; GRUB automatically sets the root device to
`(cd)' when booted from a CD-ROM. It is only necessary to refer to
`(cd)' if you want to access other drives as well.


File: grub.info,  Node: Making a GRUB bootable CD-ROM-Footnotes,  Up: Making a GRUB bootable CD-ROM

   (1) El Torito is a specification for bootable CD using BIOS
functions.


File: grub.info,  Node: Booting,  Next: Configuration,  Prev: Installation,  Up: Top

4 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
* OS-specific notes::           Notes on some operating systems


File: grub.info,  Node: General boot methods,  Next: OS-specific notes,  Up: Booting

4.1 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::


File: grub.info,  Node: Loading an operating system directly,  Next: Chain-loading,  Up: General boot methods

4.1.1 How to boot an OS directly with GRUB
------------------------------------------

Multiboot (*note Multiboot Specification: (multiboot)Top.) 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 (*note
Chain-loading::).

   FIXME: this section is incomplete.

  1. Run the command `boot' (*note boot::).

   However, DOS and Windows have some deficiencies, so you might have to
use more complicated instructions. *Note DOS/Windows::, for more
information.


File: grub.info,  Node: Chain-loading,  Prev: Loading an operating system directly,  Up: General boot methods

4.1.2 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 `chainloader' command (*note 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:

menuentry "Windows" {
	insmod chain
	insmod ntfs
	set root=(hd0,1)
	chainloader +1
}

   On systems with multiple hard disks, an additional workaround may be
required.  *Note DOS/Windows::.

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


File: grub.info,  Node: OS-specific notes,  Prev: General boot methods,  Up: Booting

4.2 Some caveats on OS-specific issues
======================================

Here, we describe some caveats on several operating systems.

* Menu:

* GNU/Hurd::
* GNU/Linux::
* DOS/Windows::
* SCO UnixWare::
* QNX::


File: grub.info,  Node: GNU/Hurd,  Next: GNU/Linux,  Up: OS-specific notes

4.2.1 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.

   FIXME: this section is incomplete.

  1. Run the command `boot' (*note boot::).


File: grub.info,  Node: GNU/Linux,  Next: DOS/Windows,  Prev: GNU/Hurd,  Up: OS-specific notes

4.2.2 GNU/Linux
---------------

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

   FIXME: this section is incomplete.

  1. Set GRUB's root device to the same drive as GNU/Linux's.

  2. Finally, run the command `boot' (*note boot::).

   *Caution:* If you use an initrd and specify the `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 `uppermem' _before_ loading the kernel. *Note uppermem::,
for more information.


File: grub.info,  Node: DOS/Windows,  Next: SCO UnixWare,  Prev: GNU/Linux,  Up: OS-specific notes

4.2.3 DOS/Windows
-----------------

GRUB cannot boot DOS or Windows directly, so you must chain-load them
(*note 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 a helper function.

   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 `drivemap' (*note drivemap::), like this:

     drivemap -s (hd0) (hd1)

   This performs a "virtual" swap between your first and second hard
drive.

   *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 "hides" a DOS (or Windows) partition (*note parttool::), DOS
(or Windows) will ignore the partition. If GRUB "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:

     parttool (hd0,1) hidden-
     parttool (hd0,2) hidden+
     set root=(hd0,1)
     chainloader +1
     parttool ${root} boot+
     boot


File: grub.info,  Node: SCO UnixWare,  Next: QNX,  Prev: DOS/Windows,  Up: OS-specific notes

4.2.4 SCO UnixWare
------------------

It is known that the signature in the boot loader for SCO UnixWare is
wrong, so you will have to specify the option `--force' to
`chainloader' (*note chainloader::), like this:

     set root=(hd1,1)
     chainloader --force +1
     parttool ${root} boot+
     boot


File: grub.info,  Node: QNX,  Prev: SCO UnixWare,  Up: OS-specific notes

4.2.5 QNX
---------

QNX seems to use a bigger boot loader, so you need to boot it up, like
this:

     set root=(hd1,2)
     chainloader +4
     boot


File: grub.info,  Node: Configuration,  Next: Network,  Prev: Booting,  Up: Top

5 Writing your own configuration file
*************************************

GRUB is configured using `grub.cfg', usually located under
`/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


File: grub.info,  Node: Simple configuration,  Next: Shell-like scripting,  Up: Configuration

5.1 Simple configuration handling
=================================

The program `grub-mkconfig' (*note Invoking grub-mkconfig::) generates
`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.

   The file `/etc/default/grub' controls the operation of
`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 `KEY=value'
lines, but if the value contains spaces or other special characters
then it must be quoted.  For example:

     GRUB_TERMINAL_INPUT="console serial"

   Valid keys in `/etc/default/grub' are as follows:

`GRUB_DEFAULT'
     The default menu entry.  This may be a number, in which case it
     identifies the Nth entry in the generated menu counted from zero,
     or the full name of a menu entry, or the special string `saved'.
     Using the full name may be useful if you want to set a menu entry
     as the default even though there may be a variable number of
     entries before it.

     If you set this to `saved', then the default menu entry will be
     that saved by `GRUB_SAVEDEFAULT', `grub-set-default', or
     `grub-reboot'.

     The default is `0'.

`GRUB_SAVEDEFAULT'
     If this option is set to `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 `GRUB_DEFAULT=saved'; it is a separate
     option because `GRUB_DEFAULT=saved' is useful without this option,
     in conjunction with `grub-set-default' or `grub-reboot'.  Unset by
     default.

`GRUB_TIMEOUT'
     Boot the default entry this many seconds after the menu is
     displayed, unless a key is pressed.  The default is `5'.  Set to
     `0' to boot immediately without displaying the menu, or to `-1' to
     wait indefinitely.

`GRUB_HIDDEN_TIMEOUT'
     Wait this many seconds for a key to be pressed before displaying
     the menu.  If no key is pressed during that time, boot
     immediately.  Unset by default.

`GRUB_HIDDEN_TIMEOUT_QUIET'
     In conjunction with `GRUB_HIDDEN_TIMEOUT', set this to `true' to
     suppress the verbose countdown while waiting for a key to be
     pressed before displaying the menu.  Unset by default.

`GRUB_DEFAULT_BUTTON'
`GRUB_TIMEOUT_BUTTON'
`GRUB_HIDDEN_TIMEOUT_BUTTON'
`GRUB_BUTTON_CMOS_ADDRESS'
     Variants of the corresponding variables without the `_BUTTON'
     suffix, used to support vendor-specific power buttons.  *Note
     Vendor power-on keys::.

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

`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
     `console' (PC BIOS and EFI consoles), `serial' (serial terminal),
     `ofconsole' (Open Firmware console), `at_keyboard' (PC AT
     keyboard, mainly useful with Coreboot), or `usb_keyboard' (USB
     keyboard 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.

`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
     `console' (PC BIOS and EFI consoles), `serial' (serial terminal),
     `gfxterm' (graphics-mode output), `ofconsole' (Open Firmware
     console), or `vga_text' (VGA text output, mainly useful with
     Coreboot).

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

`GRUB_TERMINAL'
     If this option is set, it overrides both `GRUB_TERMINAL_INPUT' and
     `GRUB_TERMINAL_OUTPUT' to the same value.

`GRUB_SERIAL_COMMAND'
     A command to configure the serial port when using the serial
     console.  *Note serial::.  Defaults to `serial'.

`GRUB_CMDLINE_LINUX'
     Command-line arguments to add to menu entries for the Linux kernel.

`GRUB_CMDLINE_LINUX_DEFAULT'
     Unless `GRUB_DISABLE_LINUX_RECOVERY' is set, two menu entries will
     be generated for each Linux kernel: one default entry and one
     entry for recovery mode.  This option lists command-line arguments
     to add only to the default menu entry, after those listed in
     `GRUB_CMDLINE_LINUX'.

`GRUB_CMDLINE_NETBSD'
`GRUB_CMDLINE_NETBSD_DEFAULT'
     As `GRUB_CMDLINE_LINUX' and `GRUB_CMDLINE_LINUX_DEFAULT', but for
     NetBSD.

`GRUB_DISABLE_LINUX_UUID'
     Normally, `grub-mkconfig' will generate menu entries that use
     universally-unique identifiers (UUIDs) to identify the root
     filesystem to the Linux kernel, using a `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 `true'.

`GRUB_DISABLE_LINUX_RECOVERY'
     Disable the generation of recovery mode menu entries for Linux.

`GRUB_DISABLE_NETBSD_RECOVERY'
     Disable the generation of recovery mode menu entries for NetBSD.

`GRUB_GFXMODE'
     Set the resolution used on the `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 available.  The default is `640x480'.

`GRUB_BACKGROUND'
     Set a background image for use with the `gfxterm' graphical
     terminal.  The value of this option must be a file readable by
     GRUB at boot time, and it must end with `.png', `.tga', `.jpg', or
     `.jpeg'.  The image will be scaled if necessary to fit the screen.

`GRUB_THEME'
     Set a theme for use with the `gfxterm' graphical terminal.  *Note
     Themes::.

`GRUB_GFXPAYLOAD_LINUX'
     Set to `text' to force the Linux kernel to boot in normal text
     mode, `keep' to preserve the graphics mode set using
     `GRUB_GFXMODE', `WIDTHxHEIGHT'[`xDEPTH'] to set a particular
     graphics mode, or a sequence of these separated by commas or
     semicolons to try several modes in sequence.

     Depending on your kernel, your distribution, your graphics card,
     and the phase of the moon, note that using this option may cause
     GNU/Linux to suffer from various display problems, particularly
     during the early part of the boot sequence.  If you have problems,
     simply unset this option and GRUB will tell Linux to boot in
     normal text mode.

`GRUB_DISABLE_OS_PROBER'
     Normally, `grub-mkconfig' will try to use the external `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 `true' to disable this.

`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 *note play::.

   For more detailed customisation of `grub-mkconfig''s output, you may
edit the scripts in `/etc/grub.d' directly.  `/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.


File: grub.info,  Node: Shell-like scripting,  Prev: Simple configuration,  Up: Configuration

5.2 Writing full configuration files directly
=============================================


File: grub.info,  Node: Serial terminal,  Next: Vendor power-on keys,  Prev: Network,  Up: Top

6 Using GRUB via a serial line
******************************

This chapter describes how to use the serial terminal support in GRUB.

   If you have many computers or computers with no display/keyboard, it
could be very useful to control the computers through serial
communications. To connect one computer with another via a serial line,
you need to prepare a null-modem (cross) serial cable, and you may need
to have multiport serial boards, if your computer doesn't have extra
serial ports. In addition, a terminal emulator is also required, such as
minicom. Refer to a manual of your operating system, for more
information.

   As for GRUB, the instruction to set up a serial terminal is quite
simple. First of all, make sure that you haven't specified the option
`--disable-serial' to the configure script when you built your GRUB
images. If you get them in binary form, probably they have serial
terminal support already.

   Then, initialize your serial terminal after GRUB starts up. Here is
an example:

     grub> serial --unit=0 --speed=9600
     grub> terminal serial

   The command `serial' initializes the serial unit 0 with the speed
9600bps. The serial unit 0 is usually called `COM1', so, if you want to
use COM2, you must specify `--unit=1' instead. This command accepts
many other options, so please refer to *note serial::, for more details.

   The command `terminal' (*note terminal::) chooses which type of
terminal you want to use. In the case above, the terminal will be a
serial terminal, but you can also pass `console' to the command, as
`terminal serial console'. In this case, a terminal in which you press
any key will be selected as a GRUB terminal.

   However, note that GRUB assumes that your terminal emulator is
compatible with VT100 by default. This is true for most terminal
emulators nowadays, but you should pass the option `--dumb' to the
command if your terminal emulator is not VT100-compatible or implements
few VT100 escape sequences. If you specify this option then GRUB
provides you with an alternative menu interface, because the normal
menu requires several fancy features of your terminal.


File: grub.info,  Node: Vendor power-on keys,  Next: Preset Menu,  Prev: Serial terminal,  Up: Top

7 Using GRUB with vendor power-on keys
**************************************

Some laptop vendor provide an additional power-on button which boots
another OS.  GRUB supports such buttons with GRUB_TIMEOUT_BUTTON,
GRUB_DEFAULT_BUTTON, GRUB_HIDDEN_TIMEOUT_BUTTON and
GRUB_BUTTON_CMOS_ADDRESS variables in default/grub.
GRUB_TIMEOUT_BUTTON, GRUB_DEFAULT_BUTTON and GRUB_HIDDEN_TIMEOUT_BUTTON
are used instead of corresponding variables without _BUTTON suffix when
powered using special button.  GRUB_BUTTON_CMOS_ADDRESS is vendor
specific and partially model-specific.  Values known to GRUB team are:

<Dell XPS M1530>
     85:3

   To take full advantage of this function install GRUB into MBR.


File: grub.info,  Node: Filesystem,  Next: Interface,  Prev: Images,  Up: Top

8 Filesystem syntax and semantics
*********************************

GRUB uses a special syntax for specifying disk drives which can be
accessed by BIOS. Because of BIOS limitations, GRUB cannot distinguish
between IDE, ESDI, SCSI, or others. You must know yourself which BIOS
device is equivalent to which OS device. Normally, that will be clear if
you see the files in a device or use the command `find' (*note find::).

* Menu:

* Device syntax::               How to specify devices
* File name syntax::            How to specify files
* Block list syntax::           How to specify block lists


File: grub.info,  Node: Device syntax,  Next: File name syntax,  Up: Filesystem

8.1 How to specify devices
==========================

The device syntax is like this:

     `(DEVICE[,PART-NUM][,BSD-SUBPART-LETTER])'

   `[]' means the parameter is optional. DEVICE should be either `fd'
or `hd' followed by a digit, like `fd0'.  But you can also set DEVICE
to a hexadecimal or a decimal number which is a BIOS drive number, so
the following are equivalent:

     (hd0)
     (0x80)
     (128)

   PART-NUM represents the partition number of DEVICE, starting from
one for primary partitions and from five for extended partitions, and
BSD-SUBPART-LETTER represents the BSD disklabel subpartition, such as
`a' or `e'.

   A shortcut for specifying BSD subpartitions is
`(DEVICE,BSD-SUBPART-LETTER)', in this case, GRUB searches for the
first PC partition containing a BSD disklabel, then finds the
subpartition BSD-SUBPART-LETTER. Here is an example:

     (hd0,a)

   The syntax `(hd0)' represents using the entire disk (or the MBR when
installing GRUB), while the syntax `(hd0,1)' represents using the first
partition of the disk (or the boot sector of the partition when
installing GRUB).

   If you enabled the network support, the special drive, `(nd)', is
also available. Before using the network drive, you must initialize the
network. *Note Network::, for more information.

   If you boot GRUB from a CD-ROM, `(cd)' is available. *Note Making a
GRUB bootable CD-ROM::, for details.


File: grub.info,  Node: File name syntax,  Next: Block list syntax,  Prev: Device syntax,  Up: Filesystem

8.2 How to specify files
========================

There are two ways to specify files, by "absolute file name" and by
"block list".

   An absolute file name resembles a Unix absolute file name, using `/'
for the directory separator (not `\' as in DOS). One example is
`(hd0,1)/boot/grub/grub.cfg'. This means the file `/boot/grub/grub.cfg'
in the first partition of the first hard disk. If you omit the device
name in an absolute file name, GRUB uses GRUB's "root device"
implicitly. So if you set the root device to, say, `(hd1,1)' by the
command `root' (*note root::), then `/boot/kernel' is the same as
`(hd1,1)/boot/kernel'.


File: grub.info,  Node: Block list syntax,  Prev: File name syntax,  Up: Filesystem

8.3 How to specify block lists
==============================

A block list is used for specifying a file that doesn't appear in the
filesystem, like a chainloader. The syntax is
`[OFFSET]+LENGTH[,[OFFSET]+LENGTH]...'.  Here is an example:

     `0+100,200+1,300+300'

   This represents that GRUB should read blocks 0 through 99, block 200,
and blocks 300 through 599. If you omit an offset, then GRUB assumes
the offset is zero.

   Like the file name syntax (*note File name syntax::), if a blocklist
does not contain a device name, then GRUB uses GRUB's "root device". So
`(hd0,2)+1' is the same as `+1' when the root device is `(hd0,2)'.


File: grub.info,  Node: Interface,  Next: Commands,  Prev: Filesystem,  Up: Top

9 GRUB's user interface
***********************

GRUB has both a simple menu interface for choosing preset entries from a
configuration file, and a highly flexible command-line for performing
any desired combination of boot commands.

   GRUB looks for its configuration file as soon as it is loaded. If one
is found, then the full menu interface is activated using whatever
entries were found in the file. If you choose the "command-line" menu
option, or if the configuration file was not found, then GRUB drops to
the command-line interface.

* Menu:

* Command-line interface::      The flexible command-line interface
* Menu interface::              The simple menu interface
* Menu entry editor::           Editing a menu entry


File: grub.info,  Node: Command-line interface,  Next: Menu interface,  Up: Interface

9.1 The flexible command-line interface
=======================================

The command-line interface provides a prompt and after it an editable
text area much like a command-line in Unix or DOS. Each command is
immediately executed after it is entered(1) (*note Command-line
interface-Footnote-1::). The commands (*note Command-line and menu
entry commands::) are a subset of those available in the configuration
file, used with exactly the same syntax.

   Cursor movement and editing of the text on the line can be done via a
subset of the functions available in the Bash shell:

<C-f>
<PC right key>
     Move forward one character.

<C-b>
<PC left key>
     Move back one character.

<C-a>
<HOME>
     Move to the start of the line.

<C-e>
<END>
     Move the the end of the line.

<C-d>
<DEL>
     Delete the character underneath the cursor.

<C-h>
<BS>
     Delete the character to the left of the cursor.

<C-k>
     Kill the text from the current cursor position to the end of the
     line.

<C-u>
     Kill backward from the cursor to the beginning of the line.

<C-y>
     Yank the killed text back into the buffer at the cursor.

<C-p>
<PC up key>
     Move up through the history list.

<C-n>
<PC down key>
     Move down through the history list.

   When typing commands interactively, if the cursor is within or before
the first word in the command-line, pressing the <TAB> key (or <C-i>)
will display a listing of the available commands, and if the cursor is
after the first word, the `<TAB>' will provide a completion listing of
disks, partitions, and file names depending on the context. Note that
to obtain a list of drives, one must open a parenthesis, as `root ('.

   Note that you cannot use the completion functionality in the TFTP
filesystem. This is because TFTP doesn't support file name listing for
the security.


File: grub.info,  Node: Command-line interface-Footnotes,  Up: Command-line interface

   (1) However, this behavior will be changed in the future version, in
a user-invisible way.


File: grub.info,  Node: Menu interface,  Next: Menu entry editor,  Prev: Command-line interface,  Up: Interface

9.2 The simple menu interface
=============================

The menu interface is quite easy to use. Its commands are both
reasonably intuitive and described on screen.

   Basically, the menu interface provides a list of "boot entries" to
the user to choose from. Use the arrow keys to select the entry of
choice, then press <RET> to run it.  An optional timeout is available
to boot the default entry (the first one if not set), which is aborted
by pressing any key.

   Commands are available to enter a bare command-line by pressing <c>
(which operates exactly like the non-config-file version of GRUB, but
allows one to return to the menu if desired by pressing <ESC>) or to
edit any of the "boot entries" by pressing <e>.

   If you protect the menu interface with a password (*note Security::),
all you can do is choose an entry by pressing <RET>, or press <p> to
enter the password.


File: grub.info,  Node: Menu entry editor,  Prev: Menu interface,  Up: Interface

9.3 Editing a menu entry
========================

The menu entry editor looks much like the main menu interface, but the
lines in the menu are individual commands in the selected entry instead
of entry names.

   If an <ESC> is pressed in the editor, it aborts all the changes made
to the configuration entry and returns to the main menu interface.

   When a particular line is selected, the editor places the user in a
special version of the GRUB command-line to edit that line.  When the
user hits <RET>, GRUB replaces the line in question in the boot entry
with the changes (unless it was aborted via <ESC>, in which case the
changes are thrown away).

   If you want to add a new line to the menu entry, press <o> if adding
a line after the current line or press <O> if before the current line.

   To delete a line, hit the key <d>. Although GRUB unfortunately does
not support "undo", you can do almost the same thing by just returning
to the main menu.


File: grub.info,  Node: Commands,  Next: Troubleshooting,  Prev: Interface,  Up: Top

10 The list of available commands
*********************************

In this chapter, we list all commands that are available in GRUB.

   Commands belong to different groups. A few can only be used in the
global section of the configuration file (or "menu"); most of them can
be entered on the command-line and can be used either anywhere in the
menu or specifically in the menu entries.

* Menu:

* Menu-specific commands::
* General commands::
* Command-line and menu entry commands::


File: grub.info,  Node: Menu-specific commands,  Next: General commands,  Up: Commands

10.1 The list of commands for the menu only
===========================================

The semantics used in parsing the configuration file are the following:

   * The menu-specific commands have to be used before any others.

   * The files _must_ be in plain-text format.

   * `#' at the beginning of a line in a configuration file means it is
     only a comment.

   * Options are separated by spaces.

   * All numbers can be either decimal or hexadecimal. A hexadecimal
     number must be preceded by `0x', and is case-insensitive.

   * Extra options or text at the end of the line are ignored unless
     otherwise specified.

   * Unrecognized commands are added to the current entry, except
     before entries start, where they are ignored.

   These commands can only be used in the menu:

* Menu:

* menuentry::                   Start a menu entry


File: grub.info,  Node: menuentry,  Up: Menu-specific commands

10.1.1 menuentry
----------------

 -- Command: title name ...
     Start a new boot entry, and set its name to the contents of the
     rest of the line, starting with the first non-space character.


File: grub.info,  Node: General commands,  Next: Command-line and menu entry commands,  Prev: Menu-specific commands,  Up: Commands

10.2 The list of general commands
=================================

Commands usable anywhere in the menu and in the command-line.

* Menu:

* serial::                      Set up a serial device
* terminfo::                    Define terminal type


File: grub.info,  Node: serial,  Next: terminfo,  Up: General commands

10.2.1 serial
-------------

 -- Command: serial [`--unit=unit'] [`--port=port'] [`--speed=speed']
          [`--word=word'] [`--parity=parity'] [`--stop=stop']
     Initialize a serial device. UNIT is a number in the range 0-3
     specifying which serial port to use; default is 0, which
     corresponds to the port often called COM1. PORT is the I/O port
     where the UART is to be found; if specified it takes precedence
     over UNIT.  SPEED is the transmission speed; default is 9600. WORD
     and STOP are the number of data bits and stop bits. Data bits must
     be in the range 5-8 and stop bits must be 1 or 2. Default is 8 data
     bits and one stop bit. PARITY is one of `no', `odd', `even' and
     defaults to `no'.

     The serial port is not used as a communication channel unless the
     `terminal' command is used (*note terminal::).

     This command is only available if GRUB is compiled with serial
     support. See also *note Serial terminal::.


File: grub.info,  Node: terminfo,  Prev: serial,  Up: General commands

10.2.2 terminfo
---------------

 -- Command: terminfo [term]
     Define the capabilities of your terminal by giving the name of an
     entry in the terminfo database, which should correspond roughly to
     a `TERM' environment variable in Unix.

     At the moment, only `vt100' is supported in GRUB 2.  If you need
     other terminal types, please contact us to discuss the best way to
     include support for these in GRUB.

     If no option is specified, the current terminal type is printed.


File: grub.info,  Node: Command-line and menu entry commands,  Prev: General commands,  Up: Commands

10.3 The list of command-line and menu entry commands
=====================================================

These commands are usable in the command-line and in menu entries.  If
you forget a command, you can run the command `help' (*note help::).

* Menu:

* acpi::                        Load ACPI tables
* blocklist::                   Print a block list
* boot::                        Start up your operating system
* cat::                         Show the contents of a file
* chainloader::                 Chain-load another boot loader
* cmp::                         Compare two files
* configfile::                  Load a configuration file
* crc::                         Calculate CRC32 checksums
* date::                        Display or set current date and time
* drivemap::                    Map a drive to another
* echo::                        Display a line of text
* export::                      Export an environment variable
* gettext::                     Translate a string
* gptsync::                     Fill an MBR based on GPT entries
* halt::                        Shut down your computer
* help::                        Show help messages
* insmod::                      Insert a module
* keystatus::                   Check key modifier status
* ls::                          List devices or files
* parttool::                    Modify partition table entries
* play::                        Play a tune
* reboot::                      Reboot your computer
* set::                         Set an environment variable
* unset::                       Unset an environment variable


File: grub.info,  Node: acpi,  Next: blocklist,  Up: Command-line and menu entry commands

10.3.1 acpi
-----------

 -- Command: acpi [`-1'|`-2']
          [`--exclude=table1,...'|`--load-only=table1,...']
          [`--oemid=id'] [`--oemtable=table'] [`--oemtablerev=rev']
          [`--oemtablecreator=creator'] [`--oemtablecreatorrev=rev']
          [`--no-ebda'] filename ...
     Modern BIOS systems normally implement the Advanced Configuration
     and Power Interface (ACPI), and define various tables that
     describe the interface between an ACPI-compliant operating system
     and the firmware. In some cases, the tables provided by default
     only work well with certain operating systems, and it may be
     necessary to replace some of them.

     Normally, this command will replace the Root System Description
     Pointer (RSDP) in the Extended BIOS Data Area to point to the new
     tables. If the `--no-ebda' option is used, the new tables will be
     known only to GRUB, but may be used by GRUB's EFI emulation.


File: grub.info,  Node: blocklist,  Next: boot,  Prev: acpi,  Up: Command-line and menu entry commands

10.3.2 blocklist
----------------

 -- Command: blocklist file
     Print a block list (*note Block list syntax::) for FILE.


File: grub.info,  Node: boot,  Next: cat,  Prev: blocklist,  Up: Command-line and menu entry commands

10.3.3 boot
-----------

 -- Command: boot
     Boot the OS or chain-loader which has been loaded. Only necessary
     if running the fully interactive command-line (it is implicit at
     the end of a menu entry).


File: grub.info,  Node: cat,  Next: chainloader,  Prev: boot,  Up: Command-line and menu entry commands

10.3.4 cat
----------

 -- Command: cat file
     Display the contents of the file FILE. This command may be useful
     to remind you of your OS's root partition:

          grub> cat /etc/fstab


File: grub.info,  Node: chainloader,  Next: cmp,  Prev: cat,  Up: Command-line and menu entry commands

10.3.5 chainloader
------------------

 -- Command: chainloader [`--force'] file
     Load FILE as a chain-loader. Like any other file loaded by the
     filesystem code, it can use the blocklist notation (*note Block
     list syntax::) to grab the first sector of the current partition
     with `+1'.  If you specify the option `--force', then load FILE
     forcibly, whether it has a correct signature or not. This is
     required when you want to load a defective boot loader, such as
     SCO UnixWare 7.1 (*note SCO UnixWare::).


File: grub.info,  Node: cmp,  Next: configfile,  Prev: chainloader,  Up: Command-line and menu entry commands

10.3.6 cmp
----------

 -- Command: cmp file1 file2
     Compare the file FILE1 with the file FILE2. If they differ in
     size, print the sizes like this:

          Differ in size: 0x1234 [foo], 0x4321 [bar]

     If the sizes are equal but the bytes at an offset differ, then
     print the bytes like this:

          Differ at the offset 777: 0xbe [foo], 0xef [bar]

     If they are completely identical, nothing will be printed.


File: grub.info,  Node: configfile,  Next: crc,  Prev: cmp,  Up: Command-line and menu entry commands

10.3.7 configfile
-----------------

 -- Command: configfile file
     Load FILE as a configuration file.


File: grub.info,  Node: crc,  Next: date,  Prev: configfile,  Up: Command-line and menu entry commands

10.3.8 crc
----------

 -- Command: crc file
     Display the CRC32 checksum of FILE.


File: grub.info,  Node: date,  Next: drivemap,  Prev: crc,  Up: Command-line and menu entry commands

10.3.9 date
-----------

 -- Command: date [[year-]month-day] [hour:minute[:second]]
     With no arguments, print the current date and time.

     Otherwise, take the current date and time, change any elements
     specified as arguments, and set the result as the new date and
     time.  For example, `date 01-01' will set the current month and
     day to January 1, but leave the year, hour, minute, and second
     unchanged.


File: grub.info,  Node: drivemap,  Next: echo,  Prev: date,  Up: Command-line and menu entry commands

10.3.10 drivemap
----------------

 -- Command: drivemap `-l'|`-r'|[`-s'] from_drive to_drive
     Without options, map the drive FROM_DRIVE to the drive TO_DRIVE.
     This is necessary when you chain-load some operating systems, such
     as DOS, if such an OS resides at a non-first drive.  For
     convenience, any partition suffix on the drive is ignored, so you
     can safely use ${root} as a drive specification.

     With the `-s' option, perform the reverse mapping as well, swapping
     the two drives.

     With the `-l' option, list the current mappings.

     With the `-r' option, reset all mappings to the default values.

     For example:

          drivemap -s (hd0) (hd1)


File: grub.info,  Node: echo,  Next: export,  Prev: drivemap,  Up: Command-line and menu entry commands

10.3.11 echo
------------

 -- Command: echo [`-n'] [`-e'] string ...
     Display the requested text and, unless the `-n' option is used, a
     trailing new line.  If there is more than one string, they are
     separated by spaces in the output.  As usual in GRUB commands,
     variables may be substituted using `${var}'.

     The `-e' option enables interpretation of backslash escapes.  The
     following sequences are recognised:

    `\\'
          backslash

    `\a'
          alert (BEL)

    `\c'
          suppress trailing new line

    `\f'
          form feed

    `\n'
          new line

    `\r'
          carriage return

    `\t'
          horizontal tab

    `\v'
          vertical tab

     When interpreting backslash escapes, backslash followed by any
     other character will print that character.


File: grub.info,  Node: export,  Next: gettext,  Prev: echo,  Up: Command-line and menu entry commands

10.3.12 export
--------------

 -- Command: export envvar
     Export the environment variable ENVVAR. Exported variables are
     visible to subsidiary configuration files loaded using
     `configfile'.


File: grub.info,  Node: gettext,  Next: gptsync,  Prev: export,  Up: Command-line and menu entry commands

10.3.13 gettext
---------------

 -- Command: gettext string
     Translate STRING into the current language.

     The current language code is stored in the `lang' variable in
     GRUB's environment.  Translation files in MO format are read from
     `locale_dir', usually `/boot/grub/locale'.


File: grub.info,  Node: gptsync,  Next: halt,  Prev: gettext,  Up: Command-line and menu entry commands

10.3.14 gptsync
---------------

 -- Command: gptsync device [partition[+/-[type]]] ...
     Disks using the GUID Partition Table (GPT) also have a legacy
     Master Boot Record (MBR) partition table for compatibility with
     the BIOS and with older operating systems.  The legacy MBR can
     only represent a limited subset of GPT partition entries.

     This command populates the legacy MBR with the specified PARTITION
     entries on DEVICE.  Up to three partitions may be used.

     TYPE is an MBR partition type code; prefix with `0x' if you want
     to enter this in hexadecimal.  The separator between PARTITION and
     TYPE may be `+' to make the partition active, or `-' to make it
     inactive; only one partition may be active.  If both the separator
     and type are omitted, then the partition will be inactive.


File: grub.info,  Node: halt,  Next: help,  Prev: gptsync,  Up: Command-line and menu entry commands

10.3.15 halt
------------

 -- Command: halt `--no-apm'
     The command halts the computer. If the `--no-apm' option is
     specified, no APM BIOS call is performed. Otherwise, the computer
     is shut down using APM.


File: grub.info,  Node: help,  Next: insmod,  Prev: halt,  Up: Command-line and menu entry commands

10.3.16 help
------------

 -- Command: help `--all' [pattern ...]
     Display helpful information about builtin commands. If you do not
     specify PATTERN, this command shows short descriptions of most of
     available commands. If you specify the option `--all' to this
     command, short descriptions of rarely used commands (such as *note
     testload::) are displayed as well.

     If you specify any PATTERNS, it displays longer information about
     each of the commands which match those PATTERNS.


File: grub.info,  Node: insmod,  Next: keystatus,  Prev: help,  Up: Command-line and menu entry commands

10.3.17 insmod
--------------

 -- Command: insmod module
     Insert the dynamic GRUB module called MODULE.


File: grub.info,  Node: keystatus,  Next: ls,  Prev: insmod,  Up: Command-line and menu entry commands

10.3.18 keystatus
-----------------

 -- Command: keystatus [`--shift'] [`--ctrl'] [`--alt']
     Return true if the Shift, Control, or Alt modifier keys are held
     down, as requested by options. This is useful in scripting, to
     allow some user control over behaviour without having to wait for
     a keypress.

     Checking key modifier status is only supported on some platforms.
     If invoked without any options, the `keystatus' command returns
     true if and only if checking key modifier status is supported.


File: grub.info,  Node: ls,  Next: parttool,  Prev: keystatus,  Up: Command-line and menu entry commands

10.3.19 ls
----------

 -- Command: ls [arg]
     List devices or files.

     With no arguments, print all devices known to GRUB.

     If the argument is a device name enclosed in parentheses (*note
     Device syntax::), then list all files at the root directory of
     that device.

     If the argument is a directory given as an absolute file name
     (*note File name syntax::), then list the contents of that
     directory.


File: grub.info,  Node: parttool,  Next: play,  Prev: ls,  Up: Command-line and menu entry commands

10.3.20 parttool
----------------

 -- Command: parttool partition commands
     Make various modifications to partition table entries.

     Each COMMAND is either a boolean option, in which case it must be
     followed with `+' or `-' (with no intervening space) to enable or
     disable that option, or else it takes a value in the form
     `COMMAND=VALUE'.

     Currently, `parttool' is only useful on DOS partition tables (also
     known as Master Boot Record, or MBR).  On these partition tables,
     the following commands are available:

    `boot' (boolean)
          When enabled, this makes the selected partition be the active
          (bootable) partition on its disk, clearing the active flag on
          all other partitions.  This command is limited to _primary_
          partitions.

    `type' (value)
          Change the type of an existing partition.  The value must be
          a number in the range 0-0xFF (prefix with `0x' to enter it in
          hexadecimal).

    `hidden' (boolean)
          When enabled, this hides the selected partition by setting
          the "hidden" bit in its partition type code; when disabled,
          unhides the selected partition by clearing this bit.  This is
          useful only when booting DOS or Wwindows and multiple primary
          FAT partitions exist in one disk.  See also *note
          DOS/Windows::.


File: grub.info,  Node: play,  Next: reboot,  Prev: parttool,  Up: Command-line and menu entry commands

10.3.21 play
------------

 -- Command: play file | tempo [pitch1 duration1] [pitch2 duration2] ...
     Plays a tune

     If the argument is a file name (*note File name syntax::), play
     the tune recorded in it.  The file format is first the tempo as an
     unsigned 32bit little-endian number, then pairs of unsigned 16bit
     little-endian numbers for pitch and duration pairs.

     If the arguments are a series of numbers, play the inline tune.

     The tempo is the base for all note durations. 60 gives a 1-second
     base, 120 gives a half-second base, etc.  Pitches are Hz.  Set
     pitch to 0 to produce a rest.


File: grub.info,  Node: reboot,  Next: set,  Prev: play,  Up: Command-line and menu entry commands

10.3.22 reboot
--------------

 -- Command: reboot
     Reboot the computer.


File: grub.info,  Node: set,  Next: unset,  Prev: reboot,  Up: Command-line and menu entry commands

10.3.23 set
-----------

 -- Command: set [envvar=value]
     Set the environment variable ENVVAR to VALUE. If invoked with no
     arguments, print all environment variables with their values.


File: grub.info,  Node: unset,  Prev: set,  Up: Command-line and menu entry commands

10.3.24 unset
-------------

 -- Command: unset envvar
     Unset the environment variable ENVVAR.


File: grub.info,  Node: Invoking grub-install,  Next: Invoking grub-mkconfig,  Prev: Troubleshooting,  Up: Top

11 Invoking grub-install
************************

The program `grub-install' installs GRUB on your drive using
`grub-mkimage' and (on some platforms) `grub-setup'.  You must specify
the device name on which you want to install GRUB, like this:

     grub-install INSTALL_DEVICE

   The device name INSTALL_DEVICE is an OS device name or a GRUB device
name.

   `grub-install' accepts the following options:

`--help'
     Print a summary of the command-line options and exit.

`--version'
     Print the version number of GRUB and exit.

`--root-directory=DIR'
     Install GRUB images under the directory DIR instead of the root
     directory. This option is useful when you want to install GRUB
     into a separate partition or a removable disk. Here is an example
     in which you have a separate "boot" partition which is mounted on
     `/boot':

          grub-install --root-directory=/boot hd0

`--recheck'
     Recheck the device map, even if `/boot/grub/device.map' already
     exists. You should use this option whenever you add/remove a disk
     into/from your computer.


File: grub.info,  Node: Invoking grub-mkconfig,  Next: Obtaining and Building GRUB,  Prev: Invoking grub-install,  Up: Top

12 Invoking grub-mkconfig
*************************

The program `grub-mkconfig' generates a configuration file for GRUB
(*note Simple configuration::).

     grub-mkconfig -o /boot/grub/grub.cfg

   `grub-mkconfig' accepts the following options:

`--help'
     Print a summary of the command-line options and exit.

`--version'
     Print the version number of GRUB and exit.

`-o FILE'
`--output=FILE'
     Send the generated configuration file to FILE.  The default is to
     send it to standard output.


File: grub.info,  Node: Obtaining and Building GRUB,  Next: Reporting bugs,  Prev: Invoking grub-mkconfig,  Up: Top

Appendix A How to obtain and build GRUB
***************************************

     *Caution:* GRUB requires binutils-2.9.1.0.23 or later because the
     GNU assembler has been changed so that it can produce real 16bits
     machine code between 2.9.1 and 2.9.1.0.x. See
     `http://sources.redhat.com/binutils/', to obtain information on
     how to get the latest version.

   GRUB is available from the GNU alpha archive site
`ftp://alpha.gnu.org/gnu/grub' or any of its mirrors. The file will be
named grub-version.tar.gz. The current version is 1.98, so the file you
should grab is:

   `ftp://alpha.gnu.org/gnu/grub/grub-1.98.tar.gz'

   To unbundle GRUB use the instruction:

     zcat grub-1.98.tar.gz | tar xvf -

   which will create a directory called `grub-1.98' with all the
sources. You can look at the file `INSTALL' for detailed instructions
on how to build and install GRUB, but you should be able to just do:

     cd grub-1.98
     ./configure
     make install

   Also, the latest version is available from the SVN. See
`http://savannah.gnu.org/svn/?group=grub' for more information.


File: grub.info,  Node: Reporting bugs,  Next: Future,  Prev: Obtaining and Building GRUB,  Up: Top

Appendix B Reporting bugs
*************************

These are the guideline for how to report bugs. Take a look at this
list below before you submit bugs:

  1. Before getting unsettled, read this manual through and through.
     Also, see the GNU GRUB FAQ
     (http://www.gnu.org/software/grub/grub-faq.html).

  2. Always mention the information on your GRUB. The version number
     and the configuration are quite important. If you build it
     yourself, write the options specified to the configure script and
     your operating system, including the versions of gcc and binutils.

  3. If you have trouble with the installation, inform us of how you
     installed GRUB. Don't omit error messages, if any. Just `GRUB hangs
     up when it boots' is not enough.

     The information on your hardware is also essential. These are
     especially important: the geometries and the partition tables of
     your hard disk drives and your BIOS.

  4. If GRUB cannot boot your operating system, write down _everything_
     you see on the screen. Don't paraphrase them, like `The foo OS
     crashes with GRUB, even though it can boot with the bar boot
     loader just fine'. Mention the commands you executed, the messages
     printed by them, and information on your operating system
     including the version number.

  5. Explain what you wanted to do. It is very useful to know your
     purpose and your wish, and how GRUB didn't satisfy you.

  6. If you can investigate the problem yourself, please do. That will
     give you and us much more information on the problem. Attaching a
     patch is even better.

     When you attach a patch, make the patch in unified diff format, and
     write ChangeLog entries. But, even when you make a patch, don't
     forget to explain the problem, so that we can understand what your
     patch is for.

  7. Write down anything that you think might be related. Please
     understand that we often need to reproduce the same problem you
     encounterred in our environment. So your information should be
     sufficient for us to do the same thing--Don't forget that we
     cannot see your computer directly. If you are not sure whether to
     state a fact or leave it out, state it!  Reporting too many things
     is much better than omitting something important.

   If you follow the guideline above, submit a report to the Bug
Tracking System (http://savannah.gnu.org/bugs/?group=grub).
Alternatively, you can submit a report via electronic mail to
<bug-grub@gnu.org>, but we strongly recommend that you use the Bug
Tracking System, because e-mail can be passed over easily.

   Once we get your report, we will try to fix the bugs.


File: grub.info,  Node: Future,  Next: Internals,  Prev: Reporting bugs,  Up: Top

Appendix C Where GRUB will go
*****************************

We started the next generation of GRUB, GRUB 2. GRUB 2 includes
internationalization, dynamic module loading, real memory management,
multiple architecture support, a scripting language, and many other
nice feature. If you are interested in the development of GRUB 2, take
a look at the homepage (http://www.gnu.org/software/grub/grub.html).


File: grub.info,  Node: Copying This Manual,  Next: Index,  Prev: Internals,  Up: Top

Appendix D Copying This Manual
******************************

* Menu:

* GNU Free Documentation License::  License for copying this manual.


File: grub.info,  Node: GNU Free Documentation License,  Up: Copying This Manual

D.1 GNU Free Documentation License
==================================

                      Version 1.2, November 2002

     Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
     51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA

     Everyone is permitted to copy and distribute verbatim copies
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     This License is a kind of "copyleft", which means that derivative
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     It complements the GNU General Public License, which is a copyleft
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     We have designed this License in order to use it for manuals for
     free software, because free software needs free documentation: a
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     passage of Front-Cover Text and one of Back-Cover Text may be
     added by (or through arrangements made by) any one entity.  If the
     Document already includes a cover text for the same cover,
     previously added by you or by arrangement made by the same entity
     you are acting on behalf of, you may not add another; but you may
     replace the old one, on explicit permission from the previous
     publisher that added the old one.

     The author(s) and publisher(s) of the Document do not by this
     License give permission to use their names for publicity for or to
     assert or imply endorsement of any Modified Version.

  5. COMBINING DOCUMENTS

     You may combine the Document with other documents released under
     this License, under the terms defined in section 4 above for
     modified versions, provided that you include in the combination
     all of the Invariant Sections of all of the original documents,
     unmodified, and list them all as Invariant Sections of your
     combined work in its license notice, and that you preserve all
     their Warranty Disclaimers.

     The combined work need only contain one copy of this License, and
     multiple identical Invariant Sections may be replaced with a single
     copy.  If there are multiple Invariant Sections with the same name
     but different contents, make the title of each such section unique
     by adding at the end of it, in parentheses, the name of the
     original author or publisher of that section if known, or else a
     unique number.  Make the same adjustment to the section titles in
     the list of Invariant Sections in the license notice of the
     combined work.

     In the combination, you must combine any sections Entitled
     "History" in the various original documents, forming one section
     Entitled "History"; likewise combine any sections Entitled
     "Acknowledgements", and any sections Entitled "Dedications".  You
     must delete all sections Entitled "Endorsements."

  6. COLLECTIONS OF DOCUMENTS

     You may make a collection consisting of the Document and other
     documents released under this License, and replace the individual
     copies of this License in the various documents with a single copy
     that is included in the collection, provided that you follow the
     rules of this License for verbatim copying of each of the
     documents in all other respects.

     You may extract a single document from such a collection, and
     distribute it individually under this License, provided you insert
     a copy of this License into the extracted document, and follow
     this License in all other respects regarding verbatim copying of
     that document.

  7. AGGREGATION WITH INDEPENDENT WORKS

     A compilation of the Document or its derivatives with other
     separate and independent documents or works, in or on a volume of
     a storage or distribution medium, is called an "aggregate" if the
     copyright resulting from the compilation is not used to limit the
     legal rights of the compilation's users beyond what the individual
     works permit.  When the Document is included in an aggregate, this
     License does not apply to the other works in the aggregate which
     are not themselves derivative works of the Document.

     If the Cover Text requirement of section 3 is applicable to these
     copies of the Document, then if the Document is less than one half
     of the entire aggregate, the Document's Cover Texts may be placed
     on covers that bracket the Document within the aggregate, or the
     electronic equivalent of covers if the Document is in electronic
     form.  Otherwise they must appear on printed covers that bracket
     the whole aggregate.

  8. TRANSLATION

     Translation is considered a kind of modification, so you may
     distribute translations of the Document under the terms of section
     4.  Replacing Invariant Sections with translations requires special
     permission from their copyright holders, but you may include
     translations of some or all Invariant Sections in addition to the
     original versions of these Invariant Sections.  You may include a
     translation of this License, and all the license notices in the
     Document, and any Warranty Disclaimers, provided that you also
     include the original English version of this License and the
     original versions of those notices and disclaimers.  In case of a
     disagreement between the translation and the original version of
     this License or a notice or disclaimer, the original version will
     prevail.

     If a section in the Document is Entitled "Acknowledgements",
     "Dedications", or "History", the requirement (section 4) to
     Preserve its Title (section 1) will typically require changing the
     actual title.

  9. TERMINATION

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

 10. FUTURE REVISIONS OF THIS LICENSE

     The Free Software Foundation may publish new, revised versions of
     the GNU Free Documentation License from time to time.  Such new
     versions will be similar in spirit to the present version, but may
     differ in detail to address new problems or concerns.  See
     `http://www.gnu.org/copyleft/'.

     Each version of the License is given a distinguishing version
     number.  If the Document specifies that a particular numbered
     version of this License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that specified version or of any later version that has been
     published (not as a draft) by the Free Software Foundation.  If
     the Document does not specify a version number of this License,
     you may choose any version ever published (not as a draft) by the
     Free Software Foundation.

D.1.1 ADDENDUM: How to use this License for your documents
----------------------------------------------------------

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

       Copyright (C)  YEAR  YOUR NAME.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.2
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

   If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:

         with the Invariant Sections being LIST THEIR TITLES, with
         the Front-Cover Texts being LIST, and with the Back-Cover Texts
         being LIST.

   If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

   If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.


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