10
@c Unify all our little indices for now.
17
@footnotestyle separate
23
* GRUB: (grub). The GRand Unified Bootloader
24
* grub-install: (grub)Invoking grub-install. Install GRUB on your drive
25
* grub-md5-crypt: (grub)Invoking grub-md5-crypt. Encrypt a password
27
* grub-terminfo: (grub)Invoking grub-terminfo. Generate a terminfo
30
* grub-set-default: (grub)Invoking grub-set-default. Set a default boot
32
* mbchk: (grub)Invoking mbchk. Check for the format of a Multiboot kernel
35
@setchapternewpage odd
38
Copyright @copyright{} 1999,2000,2001,2002,2004 Free Software Foundation, Inc.
40
Permission is granted to make and distribute verbatim copies of
41
this manual provided the copyright notice and this permission notice
42
are preserved on all copies.
45
Permission is granted to process this file through TeX and print the
46
results, provided the printed document carries a copying permission
47
notice identical to this one except for the removal of this paragraph
48
(this paragraph not being relevant to the printed manual).
52
Permission is granted to copy and distribute modified versions of this
53
manual under the conditions for verbatim copying, provided also that
54
the entire resulting derived work is distributed under the terms of a
55
permission notice identical to this one.
57
Permission is granted to copy and distribute translations of this manual
58
into another language, under the above conditions for modified versions.
63
@title the GRUB manual
64
@subtitle The GRand Unified Bootloader, version @value{VERSION}, @value{UPDATED}.
65
@author Gordon Matzigkeit
66
@author Yoshinori K. Okuji
67
@c The following two commands start the copyright page.
69
@vskip 0pt plus 1filll
70
Copyright @copyright{} 1999,2000,2001,2002,2004 Free Software Foundation, Inc.
72
Permission is granted to make and distribute verbatim copies of
73
this manual provided the copyright notice and this permission notice
74
are preserved on all copies.
75
Permission is granted to copy and distribute modified versions of this
76
manual under the conditions for verbatim copying, provided that the entire
77
resulting derived work is distributed under the terms of a permission
78
notice identical to this one.
80
Permission is granted to copy and distribute translations of this manual
81
into another language, under the above conditions for modified versions,
82
except that this permission notice may be stated in a translation approved
83
by Free Software Foundation.
86
@c Output the table of contents at the beginning.
96
This is the documentation of GNU GRUB, the GRand Unified Bootloader,
97
a flexible and powerful boot loader program for @sc{pc}s.
99
This edition documents version @value{VERSION}.
103
* Introduction:: Capturing the spirit of GRUB
104
* Naming convention:: Names of your drives in GRUB
105
* Installation:: Installing GRUB on your drive
106
* Booting:: How to boot different operating systems
107
* Configuration:: Writing your own configuration file
108
* Network:: Downloading OS images from a network
109
* Serial terminal:: Using GRUB via a serial line
110
* Preset Menu:: Embedding a configuration file into GRUB
111
* Security:: Improving the security
112
* Images:: GRUB image files
113
* Filesystem:: Filesystem syntax and semantics
114
* Interface:: The menu and the command-line
115
* Commands:: The list of available builtin commands
116
* Troubleshooting:: Error messages produced by GRUB
117
* Invoking the grub shell:: How to use the grub shell
118
* Invoking grub-install:: How to use the GRUB installer
119
* Invoking grub-md5-crypt:: How to generate a cryptic password
120
* Invoking grub-terminfo:: How to generate a terminfo command
121
* Invoking grub-set-default:: How to set a default boot entry
122
* Invoking mbchk:: How to use the Multiboot checker
123
* Obtaining and Building GRUB:: How to obtain and build GRUB
124
* Reporting bugs:: Where you should send a bug report
125
* Future:: Some future plans on GRUB
126
* Internals:: Hacking GRUB
132
@chapter Introduction to GRUB
135
* Overview:: What exactly GRUB is and how to use it
136
* History:: From maggot to house fly
137
* Features:: GRUB features
138
* Role of a boot loader:: The role of a boot loader
145
Briefly, a @dfn{boot loader} is the first software program that runs when
146
a computer starts. It is responsible for loading and transferring
147
control to an operating system @dfn{kernel} software (such as Linux or
148
GNU Mach). The kernel, in turn, initializes the rest of the operating
149
system (e.g. a GNU system).
151
GNU GRUB is a very powerful boot loader, which can load a wide variety
152
of free operating systems, as well as proprietary operating systems with
153
chain-loading@footnote{@dfn{chain-load} is the mechanism for loading
154
unsupported operating systems by loading another boot loader. It is
155
typically used for loading DOS or Windows.}. GRUB is designed to
156
address the complexity of booting a personal computer; both the
157
program and this manual are tightly bound to that computer platform,
158
although porting to other platforms may be addressed in the future.
160
One of the important features in GRUB is flexibility; GRUB understands
161
filesystems and kernel executable formats, so you can load an arbitrary
162
operating system the way you like, without recording the physical
163
position of your kernel on the disk. Thus you can load the kernel
164
just by specifying its file name and the drive and partition where the
167
When booting with GRUB, you can use either a command-line interface
168
(@pxref{Command-line interface}), or a menu interface (@pxref{Menu
169
interface}). Using the command-line interface, you type the drive
170
specification and file name of the kernel manually. In the menu
171
interface, you just select an OS using the arrow keys. The menu is
172
based on a configuration file which you prepare beforehand
173
(@pxref{Configuration}). While in the menu, you can switch to the
174
command-line mode, and vice-versa. You can even edit menu entries
177
In the following chapters, you will learn how to specify a drive, a
178
partition, and a file name (@pxref{Naming convention}) to GRUB, how to
179
install GRUB on your drive (@pxref{Installation}), and how to boot your
180
OSes (@pxref{Booting}), step by step.
182
Besides the GRUB boot loader itself, there is a @dfn{grub shell}
183
@command{grub} (@pxref{Invoking the grub shell}) which can be run when
184
you are in your operating system. It emulates the boot loader and can
185
be used for installing the boot loader.
189
@section History of GRUB
191
GRUB originated in 1995 when Erich Boleyn was trying to boot the GNU
192
Hurd with the University of Utah's Mach 4 microkernel (now known as GNU
193
Mach). Erich and Brian Ford designed the Multiboot Specification
194
(@pxref{Top, Multiboot Specification, Motivation, multiboot, The Multiboot
195
Specification}), because they were determined not to add to the large
196
number of mutually-incompatible PC boot methods.
198
Erich then began modifying the FreeBSD boot loader so that it would
199
understand Multiboot. He soon realized that it would be a lot easier
200
to write his own boot loader from scratch than to keep working on the
201
FreeBSD boot loader, and so GRUB was born.
203
Erich added many features to GRUB, but other priorities prevented him
204
from keeping up with the demands of its quickly-expanding user base. In
205
1999, Gordon Matzigkeit and Yoshinori K. Okuji adopted GRUB as an
206
official GNU package, and opened its development by making the latest
207
sources available via anonymous CVS. @xref{Obtaining and Building
208
GRUB}, for more information.
212
@section GRUB features
214
The primary requirement for GRUB is that it be compliant with the
215
@dfn{Multiboot Specification}, which is described in @ref{Top, Multiboot
216
Specification, Motivation, multiboot, The Multiboot Specification}.
218
The other goals, listed in approximate order of importance, are:
222
Basic functions must be straightforward for end-users.
225
Rich functionality to support kernel experts and designers.
228
Backward compatibility for booting FreeBSD, NetBSD, OpenBSD, and
229
Linux. Proprietary kernels (such as DOS, Windows NT, and OS/2) are
230
supported via a chain-loading function.
233
Except for specific compatibility modes (chain-loading and the Linux
234
@dfn{piggyback} format), all kernels will be started in much the same
235
state as in the Multiboot Specification. Only kernels loaded at 1 megabyte
236
or above are presently supported. Any attempt to load below that
237
boundary will simply result in immediate failure and an error message
238
reporting the problem.
240
In addition to the requirements above, GRUB has the following features
241
(note that the Multiboot Specification doesn't require all the features
245
@item Recognize multiple executable formats
246
Support many of the @dfn{a.out} variants plus @dfn{ELF}. Symbol
247
tables are also loaded.
249
@item Support non-Multiboot kernels
250
Support many of the various free 32-bit kernels that lack Multiboot
251
compliance (primarily FreeBSD, NetBSD, OpenBSD, and
252
Linux). Chain-loading of other boot loaders is also supported.
254
@item Load multiples modules
255
Fully support the Multiboot feature of loading multiple modules.
257
@item Load a configuration file
258
Support a human-readable text configuration file with preset boot
259
commands. You can also load another configuration file dynamically and
260
embed a preset configuration file in a GRUB image file. The list of
261
commands (@pxref{Commands}) are a superset of those supported on the
262
command-line. An example configuration file is provided in
265
@item Provide a menu interface
266
A menu interface listing preset boot commands, with a programmable
267
timeout, is available. There is no fixed limit on the number of boot
268
entries, and the current implementation has space for several hundred.
270
@item Have a flexible command-line interface
271
A fairly flexible command-line interface, accessible from the menu,
272
is available to edit any preset commands, or write a new boot command
273
set from scratch. If no configuration file is present, GRUB drops to
276
The list of commands (@pxref{Commands}) are a subset of those supported
277
for configuration files. Editing commands closely resembles the Bash
278
command-line (@pxref{Command Line Editing, Bash, Command Line Editing,
279
features, Bash Features}), with @key{TAB}-completion of commands,
280
devices, partitions, and files in a directory depending on context.
282
@item Support multiple filesystem types
283
Support multiple filesystem types transparently, plus a useful explicit
284
blocklist notation. The currently supported filesystem types are
285
@dfn{BSD FFS}, @dfn{DOS FAT16 and FAT32}, @dfn{Minix fs}, @dfn{Linux
286
ext2fs}, @dfn{ReiserFS}, @dfn{JFS}, @dfn{XFS}, and @dfn{VSTa
287
fs}. @xref{Filesystem}, for more information.
289
@item Support automatic decompression
290
Can decompress files which were compressed by @command{gzip}. This
291
function is both automatic and transparent to the user (i.e. all
292
functions operate upon the uncompressed contents of the specified
293
files). This greatly reduces a file size and loading time, a
294
particularly great benefit for floppies.@footnote{There are a few
295
pathological cases where loading a very badly organized ELF kernel might
296
take longer, but in practice this never happen.}
298
It is conceivable that some kernel modules should be loaded in a
299
compressed state, so a different module-loading command can be specified
300
to avoid uncompressing the modules.
302
@item Access data on any installed device
303
Support reading data from any or all floppies or hard disk(s) recognized
304
by the BIOS, independent of the setting of the root device.
306
@item Be independent of drive geometry translations
307
Unlike many other boot loaders, GRUB makes the particular drive
308
translation irrelevant. A drive installed and running with one
309
translation may be converted to another translation without any adverse
310
effects or changes in GRUB's configuration.
312
@item Detect all installed @sc{ram}
313
GRUB can generally find all the installed @sc{ram} on a PC-compatible
314
machine. It uses an advanced BIOS query technique for finding all
315
memory regions. As described on the Multiboot Specification (@pxref{Top,
316
Multiboot Specification, Motivation, multiboot, The Multiboot
317
Specification}), not all kernels make use of this information, but GRUB
318
provides it for those who do.
320
@item Support Logical Block Address mode
321
In traditional disk calls (called @dfn{CHS mode}), there is a geometry
322
translation problem, that is, the BIOS cannot access over 1024
323
cylinders, so the accessible space is limited to at least 508 MB and to
324
at most 8GB. GRUB can't universally solve this problem, as there is no
325
standard interface used in all machines. However, several newer machines
326
have the new interface, Logical Block Address (@dfn{LBA}) mode. GRUB
327
automatically detects if LBA mode is available and uses it if
328
available. In LBA mode, GRUB can access the entire disk.
330
@item Support network booting
331
GRUB is basically a disk-based boot loader but also has network
332
support. You can load OS images from a network by using the @dfn{TFTP}
335
@item Support remote terminals
336
To support computers with no console, GRUB provides remote terminal
337
support, so that you can control GRUB from a remote host. Only serial
338
terminal support is implemented at the moment.
342
@node Role of a boot loader
343
@section The role of a boot loader
345
The following is a quotation from Gordon Matzigkeit, a GRUB fanatic:
348
Some people like to acknowledge both the operating system and kernel when
349
they talk about their computers, so they might say they use
350
``GNU/Linux'' or ``GNU/Hurd''. Other people seem to think that the
351
kernel is the most important part of the system, so they like to call
352
their GNU operating systems ``Linux systems.''
354
I, personally, believe that this is a grave injustice, because the
355
@emph{boot loader} is the most important software of all. I used to
356
refer to the above systems as either ``LILO''@footnote{The LInux LOader,
357
a boot loader that everybody uses, but nobody likes.} or ``GRUB''
360
Unfortunately, nobody ever understood what I was talking about; now I
361
just use the word ``GNU'' as a pseudonym for GRUB.
363
So, if you ever hear people talking about their alleged ``GNU'' systems,
364
remember that they are actually paying homage to the best boot loader
368
We, the GRUB maintainers, do not (usually) encourage Gordon's level of
369
fanaticism, but it helps to remember that boot loaders deserve
370
recognition. We hope that you enjoy using GNU GRUB as much as we did
374
@node Naming convention
375
@chapter Naming convention
377
The device syntax used in GRUB is a wee bit different from what you may
378
have seen before in your operating system(s), and you need to know it so
379
that you can specify a drive/partition.
381
Look at the following examples and explanations:
387
First of all, GRUB requires that the device name be enclosed with
388
@samp{(} and @samp{)}. The @samp{fd} part means that it is a floppy
389
disk. The number @samp{0} is the drive number, which is counted from
390
@emph{zero}. This expression means that GRUB will use the whole floppy
397
Here, @samp{hd} means it is a hard disk drive. The first integer
398
@samp{0} indicates the drive number, that is, the first hard disk, while
399
the second integer, @samp{1}, indicates the partition number (or the
400
@sc{pc} slice number in the BSD terminology). Once again, please note
401
that the partition numbers are counted from @emph{zero}, not from
402
one. This expression means the second partition of the first hard disk
403
drive. In this case, GRUB uses one partition of the disk, instead of the
410
This specifies the first @dfn{extended partition} of the first hard disk
411
drive. Note that the partition numbers for extended partitions are
412
counted from @samp{4}, regardless of the actual number of primary
413
partitions on your hard disk.
419
This means the BSD @samp{a} partition of the second hard disk. If you
420
need to specify which @sc{pc} slice number should be used, use something
421
like this: @samp{(hd1,0,a)}. If the @sc{pc} slice number is omitted,
422
GRUB searches for the first @sc{pc} slice which has a BSD @samp{a}
425
Of course, to actually access the disks or partitions with GRUB, you
426
need to use the device specification in a command, like @samp{root
427
(fd0)} or @samp{unhide (hd0,2)}. To help you find out which number
428
specifies a partition you want, the GRUB command-line
429
(@pxref{Command-line interface}) options have argument
430
completion. This means that, for example, you only need to type
436
followed by a @key{TAB}, and GRUB will display the list of drives,
437
partitions, or file names. So it should be quite easy to determine the
438
name of your target partition, even with minimal knowledge of the
441
Note that GRUB does @emph{not} distinguish IDE from SCSI - it simply
442
counts the drive numbers from zero, regardless of their type. Normally,
443
any IDE drive number is less than any SCSI drive number, although that
444
is not true if you change the boot sequence by swapping IDE and SCSI
447
Now the question is, how to specify a file? Again, consider an
454
This specifies the file named @samp{vmlinuz}, found on the first
455
partition of the first hard disk drive. Note that the argument
456
completion works with file names, too.
458
That was easy, admit it. Now read the next chapter, to find out how to
459
actually install GRUB on your drive.
463
@chapter Installation
465
In order to install GRUB as your boot loader, you need to first
466
install the GRUB system and utilities under your UNIX-like operating
467
system (@pxref{Obtaining and Building GRUB}). You can do this either
468
from the source tarball, or as a package for your OS.
470
After you have done that, you need to install the boot loader on a
471
drive (floppy or hard disk). There are two ways of doing that - either
472
using the utility @command{grub-install} (@pxref{Invoking
473
grub-install}) on a UNIX-like OS, or by running GRUB itself from a
474
floppy. These are quite similar, however the utility might probe a
475
wrong BIOS drive, so you should be careful.
477
Also, if you install GRUB on a UNIX-like OS, please make sure that you
478
have an emergency boot disk ready, so that you can rescue your computer
479
if, by any chance, your hard drive becomes unusable (unbootable).
481
GRUB comes with boot images, which are normally put in the directory
482
@file{/usr/lib/grub/i386-pc}. If you do not use grub-install, then
483
you need to copy the files @file{stage1}, @file{stage2}, and
484
@file{*stage1_5} to the directory @file{/boot/grub}, and run the
485
@command{grub-set-default} (@pxref{Invoking grub-set-default}) if you
486
intend to use @samp{default saved} (@pxref{default}) in your
487
configuration file. Hereafter, the directory where GRUB images are
488
initially placed (normally @file{/usr/lib/grub/i386-pc}) will be
489
called the @dfn{image directory}, and the directory where the boot
490
loader needs to find them (usually @file{/boot/grub}) will be called
491
the @dfn{boot directory}.
494
* Creating a GRUB boot floppy::
495
* Installing GRUB natively::
496
* Installing GRUB using grub-install::
497
* Making a GRUB bootable CD-ROM::
501
@node Creating a GRUB boot floppy
502
@section Creating a GRUB boot floppy
504
To create a GRUB boot floppy, you need to take the files @file{stage1}
505
and @file{stage2} from the image directory, and write them to the first
506
and the second block of the floppy disk, respectively.
508
@strong{Caution:} This procedure will destroy any data currently stored
511
On a UNIX-like operating system, that is done with the following
516
# @kbd{cd /usr/lib/grub/i386-pc}
517
# @kbd{dd if=stage1 of=/dev/fd0 bs=512 count=1}
520
# @kbd{dd if=stage2 of=/dev/fd0 bs=512 seek=1}
527
The device file name may be different. Consult the manual for your OS.
530
@node Installing GRUB natively
531
@section Installing GRUB natively
533
@strong{Caution:} Installing GRUB's stage1 in this manner will erase the
534
normal boot-sector used by an OS.
536
GRUB can currently boot GNU Mach, Linux, FreeBSD, NetBSD, and OpenBSD
537
directly, so using it on a boot sector (the first sector of a
538
partition) should be okay. But generally, it would be a good idea to
539
back up the first sector of the partition on which you are installing
540
GRUB's stage1. This isn't as important if you are installing GRUB on
541
the first sector of a hard disk, since it's easy to reinitialize it
542
(e.g. by running @samp{FDISK /MBR} from DOS).
544
If you decide to install GRUB in the native environment, which is
545
definitely desirable, you'll need to create a GRUB boot disk, and
546
reboot your computer with it. Otherwise, see @ref{Installing GRUB using
549
Once started, GRUB will show the command-line interface
550
(@pxref{Command-line interface}). First, set the GRUB's @dfn{root
551
device}@footnote{Note that GRUB's root device doesn't necessarily mean
552
your OS's root partition; if you need to specify a root partition for
553
your OS, add the argument into the command @command{kernel}.} to the
554
partition containing the boot directory, like this:
557
grub> @kbd{root (hd0,0)}
560
If you are not sure which partition actually holds this directory, use the
561
command @command{find} (@pxref{find}), like this:
564
grub> @kbd{find /boot/grub/stage1}
567
This will search for the file name @file{/boot/grub/stage1} and show the
568
devices which contain the file.
570
Once you've set the root device correctly, run the command
571
@command{setup} (@pxref{setup}):
574
grub> @kbd{setup (hd0)}
577
This command will install the GRUB boot loader on the Master Boot
578
Record (MBR) of the first drive. If you want to put GRUB into the boot
579
sector of a partition instead of putting it in the MBR, specify the
580
partition into which you want to install GRUB:
583
grub> @kbd{setup (hd0,0)}
586
If you install GRUB into a partition or a drive other than the first
587
one, you must chain-load GRUB from another boot loader. Refer to the
588
manual for the boot loader to know how to chain-load GRUB.
590
After using the setup command, you will boot into GRUB without the
591
GRUB floppy. See the chapter @ref{Booting} to find out how to boot
592
your operating systems from GRUB.
595
@node Installing GRUB using grub-install
596
@section Installing GRUB using grub-install
598
@strong{Caution:} This procedure is definitely less safe, because
599
there are several ways in which your computer can become
600
unbootable. For example, most operating systems don't tell GRUB how to
601
map BIOS drives to OS devices correctly---GRUB merely @dfn{guesses}
602
the mapping. This will succeed in most cases, but not
603
always. Therefore, GRUB provides you with a map file called the
604
@dfn{device map}, which you must fix if it is wrong. @xref{Device
605
map}, for more details.
607
If you still do want to install GRUB under a UNIX-like OS (such
608
as @sc{gnu}), invoke the program @command{grub-install} (@pxref{Invoking
609
grub-install}) as the superuser (@dfn{root}).
611
The usage is basically very simple. You only need to specify one
612
argument to the program, namely, where to install the boot loader. The
613
argument can be either a device file (like @samp{/dev/hda}) or a
614
partition specified in GRUB's notation. For example, under Linux the
615
following will install GRUB into the MBR of the first IDE disk:
618
# @kbd{grub-install /dev/hda}
621
Likewise, under GNU/Hurd, this has the same effect:
624
# @kbd{grub-install /dev/hd0}
627
If it is the first BIOS drive, this is the same as well:
630
# @kbd{grub-install '(hd0)'}
633
Or you can omit the parentheses:
636
# @kbd{grub-install hd0}
639
But all the above examples assume that GRUB should use images under
640
the root directory. If you want GRUB to use images under a directory
641
other than the root directory, you need to specify the option
642
@option{--root-directory}. The typical usage is that you create a GRUB
643
boot floppy with a filesystem. Here is an example:
647
# @kbd{mke2fs /dev/fd0}
648
# @kbd{mount -t ext2 /dev/fd0 /mnt}
649
# @kbd{grub-install --root-directory=/mnt fd0}
654
Another example is when you have a separate boot partition
655
which is mounted at @file{/boot}. Since GRUB is a boot loader, it
656
doesn't know anything about mountpoints at all. Thus, you need to run
657
@command{grub-install} like this:
660
# @kbd{grub-install --root-directory=/boot /dev/hda}
663
By the way, as noted above, it is quite difficult to guess BIOS drives
664
correctly under a UNIX-like OS. Thus, @command{grub-install} will prompt
665
you to check if it could really guess the correct mappings, after the
666
installation. The format is defined in @ref{Device map}. Please be
667
quite careful. If the output is wrong, it is unlikely that your
668
computer will be able to boot with no problem.
670
Note that @command{grub-install} is actually just a shell script and the
671
real task is done by the grub shell @command{grub} (@pxref{Invoking the
672
grub shell}). Therefore, you may run @command{grub} directly to install
673
GRUB, without using @command{grub-install}. Don't do that, however,
674
unless you are very familiar with the internals of GRUB. Installing a
675
boot loader on a running OS may be extremely dangerous.
678
@node Making a GRUB bootable CD-ROM
679
@section Making a GRUB bootable CD-ROM
681
GRUB supports the @dfn{no emulation mode} in the El Torito
682
specification@footnote{El Torito is a specification for bootable CD
683
using BIOS functions.}. This means that you can use the whole CD-ROM
684
from GRUB and you don't have to make a floppy or hard disk image file,
685
which can cause compatibility problems.
687
For booting from a CD-ROM, GRUB uses a special Stage 2 called
688
@file{stage2_eltorito}. The only GRUB files you need to have in your
689
bootable CD-ROM are this @file{stage2_eltorito} and optionally a config file
690
@file{menu.lst}. You don't need to use @file{stage1} or @file{stage2},
691
because El Torito is quite different from the standard boot process.
693
Here is an example of procedures to make a bootable CD-ROM
694
image. First, make a top directory for the bootable image, say,
701
Make a directory for GRUB:
704
$ @kbd{mkdir -p iso/boot/grub}
707
Copy the file @file{stage2_eltorito}:
710
$ @kbd{cp /usr/lib/grub/i386-pc/stage2_eltorito iso/boot/grub}
713
If desired, make the config file @file{menu.lst} under @file{iso/boot/grub}
714
(@pxref{Configuration}), and copy any files and directories for the disc to the
715
directory @file{iso/}.
717
Finally, make a ISO9660 image file like this:
720
$ @kbd{mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot \
721
-boot-load-size 4 -boot-info-table -o grub.iso iso}
724
This produces a file named @file{grub.iso}, which then can be burned
725
into a CD (or a DVD). @kbd{mkisofs} has already set up the disc to boot
726
from the @kbd{boot/grub/stage2_eltorito} file, so there is no need to
727
setup GRUB on the disc. (Note that the @kbd{-boot-load-size 4} bit is
728
required for compatibility with the BIOS on many older machines.)
730
You can use the device @samp{(cd)} to access a CD-ROM in your
731
config file. This is not required; GRUB automatically sets the root device
732
to @samp{(cd)} when booted from a CD-ROM. It is only necessary to refer to
733
@samp{(cd)} if you want to access other drives as well.
739
GRUB can load Multiboot-compliant kernels in a consistent way,
740
but for some free operating systems you need to use some OS-specific
744
* General boot methods:: How to boot OSes with GRUB generally
745
* OS-specific notes:: Notes on some operating systems
746
* Making your system robust:: How to make your system robust
750
@node General boot methods
751
@section How to boot operating systems
753
GRUB has two distinct boot methods. One of the two is to load an
754
operating system directly, and the other is to chain-load another boot
755
loader which then will load an operating system actually. Generally
756
speaking, the former is more desirable, because you don't need to
757
install or maintain other boot loaders and GRUB is flexible enough to
758
load an operating system from an arbitrary disk/partition. However,
759
the latter is sometimes required, since GRUB doesn't support all the
760
existing operating systems natively.
763
* Loading an operating system directly::
768
@node Loading an operating system directly
769
@subsection How to boot an OS directly with GRUB
771
Multiboot (@pxref{Top, Multiboot Specification, Motivation, multiboot,
772
The Multiboot Specification}) is the native format supported by GRUB.
773
For the sake of convenience, there is also support for Linux, FreeBSD,
774
NetBSD and OpenBSD. If you want to boot other operating systems, you
775
will have to chain-load them (@pxref{Chain-loading}).
777
Generally, GRUB can boot any Multiboot-compliant OS in the following
782
Set GRUB's root device to the drive where the OS images are stored with
783
the command @command{root} (@pxref{root}).
786
Load the kernel image with the command @command{kernel} (@pxref{kernel}).
789
If you need modules, load them with the command @command{module}
790
(@pxref{module}) or @command{modulenounzip} (@pxref{modulenounzip}).
793
Run the command @command{boot} (@pxref{boot}).
796
Linux, FreeBSD, NetBSD and OpenBSD can be booted in a similar
797
manner. You load a kernel image with the command @command{kernel} and
798
then run the command @command{boot}. If the kernel requires some
799
parameters, just append the parameters to @command{kernel}, after the
800
file name of the kernel. Also, please refer to @ref{OS-specific notes},
801
for information on your OS-specific issues.
805
@subsection Load another boot loader to boot unsupported operating systems
807
If you want to boot an unsupported operating system (e.g. Windows 95),
808
chain-load a boot loader for the operating system. Normally, the boot
809
loader is embedded in the @dfn{boot sector} of the partition on which
810
the operating system is installed.
814
Set GRUB's root device to the partition by the command
815
@command{rootnoverify} (@pxref{rootnoverify}):
818
grub> @kbd{rootnoverify (hd0,0)}
822
Set the @dfn{active} flag in the partition using the command
823
@command{makeactive}@footnote{This is not necessary for most of the
824
modern operating systems.} (@pxref{makeactive}):
827
grub> @kbd{makeactive}
831
Load the boot loader with the command @command{chainloader}
832
(@pxref{chainloader}):
835
grub> @kbd{chainloader +1}
838
@samp{+1} indicates that GRUB should read one sector from the start of
839
the partition. The complete description about this syntax can be found
840
in @ref{Block list syntax}.
843
Run the command @command{boot} (@pxref{boot}).
846
However, DOS and Windows have some deficiencies, so you might have to
847
use more complicated instructions. @xref{DOS/Windows}, for more
851
@node OS-specific notes
852
@section Some caveats on OS-specific issues
854
Here, we describe some caveats on several operating systems.
871
Since GNU/Hurd is Multiboot-compliant, it is easy to boot it; there is
872
nothing special about it. But do not forget that you have to specify a
873
root partition to the kernel.
877
Set GRUB's root device to the same drive as GNU/Hurd's. Probably the
878
command @code{find /boot/gnumach} or similar can help you
882
Load the kernel and the module, like this:
886
grub> @kbd{kernel /boot/gnumach root=hd0s1}
887
grub> @kbd{module /boot/serverboot}
892
Run the command @command{boot} (@pxref{boot}).
897
@subsection GNU/Linux
899
It is relatively easy to boot GNU/Linux from GRUB, because it somewhat
900
resembles to boot a Multiboot-compliant OS.
904
Set GRUB's root device to the same drive as GNU/Linux's. Probably the
905
command @code{find /vmlinuz} or similar can help you (@pxref{find}).
911
grub> @kbd{kernel /vmlinuz root=/dev/hda1}
914
If you need to specify some kernel parameters, just append them to the
915
command. For example, to set @option{vga} to @samp{ext}, do this:
918
grub> @kbd{kernel /vmlinuz root=/dev/hda1 vga=ext}
921
See the documentation in the Linux source tree for complete
922
information on the available options.
925
If you use an initrd, execute the command @command{initrd}
926
(@pxref{initrd}) after @command{kernel}:
929
grub> @kbd{initrd /initrd}
933
Finally, run the command @command{boot} (@pxref{boot}).
936
@strong{Caution:} If you use an initrd and specify the @samp{mem=}
937
option to the kernel to let it use less than actual memory size, you
938
will also have to specify the same memory size to GRUB. To let GRUB know
939
the size, run the command @command{uppermem} @emph{before} loading the
940
kernel. @xref{uppermem}, for more information.
946
GRUB can load the kernel directly, either in ELF or a.out format. But
947
this is not recommended, since FreeBSD's bootstrap interface sometimes
948
changes heavily, so GRUB can't guarantee to pass kernel parameters
951
Thus, we'd recommend loading the very flexible loader
952
@file{/boot/loader} instead. See this example:
956
grub> @kbd{root (hd0,a)}
957
grub> @kbd{kernel /boot/loader}
966
GRUB can load NetBSD a.out and ELF directly, follow these steps:
970
Set GRUB's root device with @command{root} (@pxref{root}).
973
Load the kernel with @command{kernel} (@pxref{kernel}). You should
974
append the ugly option @option{--type=netbsd}, if you want to load an
975
ELF kernel, like this:
978
grub> @kbd{kernel --type=netbsd /netbsd-elf}
982
Run @command{boot} (@pxref{boot}).
985
For now, however, GRUB doesn't allow you to pass kernel parameters, so
986
it may be better to chain-load it instead. For more information, please
987
see @ref{Chain-loading}.
993
The booting instruction is exactly the same as for NetBSD
998
@subsection DOS/Windows
1000
GRUB cannot boot DOS or Windows directly, so you must chain-load them
1001
(@pxref{Chain-loading}). However, their boot loaders have some critical
1002
deficiencies, so it may not work to just chain-load them. To overcome
1003
the problems, GRUB provides you with two helper functions.
1005
If you have installed DOS (or Windows) on a non-first hard disk, you
1006
have to use the disk swapping technique, because that OS cannot boot
1007
from any disks but the first one. The workaround used in GRUB is the
1008
command @command{map} (@pxref{map}), like this:
1012
grub> @kbd{map (hd0) (hd1)}
1013
grub> @kbd{map (hd1) (hd0)}
1017
This performs a @dfn{virtual} swap between your first and second hard
1020
@strong{Caution:} This is effective only if DOS (or Windows) uses BIOS
1021
to access the swapped disks. If that OS uses a special driver for the
1022
disks, this probably won't work.
1024
Another problem arises if you installed more than one set of DOS/Windows
1025
onto one disk, because they could be confused if there are more than one
1026
primary partitions for DOS/Windows. Certainly you should avoid doing
1027
this, but there is a solution if you do want to do so. Use the partition
1028
hiding/unhiding technique.
1030
If GRUB @dfn{hide}s a DOS (or Windows) partition (@pxref{hide}), DOS (or
1031
Windows) will ignore the partition. If GRUB @dfn{unhide}s a DOS (or
1032
Windows) partition (@pxref{unhide}), DOS (or Windows) will detect the
1033
partition. Thus, if you have installed DOS (or Windows) on the first
1034
and the second partition of the first hard disk, and you want to boot
1035
the copy on the first partition, do the following:
1039
grub> @kbd{unhide (hd0,0)}
1040
grub> @kbd{hide (hd0,1)}
1041
grub> @kbd{rootnoverify (hd0,0)}
1042
grub> @kbd{chainloader +1}
1043
grub> @kbd{makeactive}
1050
@subsection SCO UnixWare
1052
It is known that the signature in the boot loader for SCO UnixWare is
1053
wrong, so you will have to specify the option @option{--force} to
1054
@command{chainloader} (@pxref{chainloader}), like this:
1058
grub> @kbd{rootnoverify (hd1,0)}
1059
grub> @kbd{chainloader --force +1}
1060
grub> @kbd{makeactive}
1069
QNX seems to use a bigger boot loader, so you need to boot it up, like
1074
grub> @kbd{rootnoverify (hd1,1)}
1075
grub> @kbd{chainloader +4}
1081
@node Making your system robust
1082
@section How to make your system robust
1084
When you test a new kernel or a new OS, it is important to make sure
1085
that your computer can boot even if the new system is unbootable. This
1086
is crucial especially if you maintain servers or remote systems. To
1087
accomplish this goal, you need to set up two things:
1091
You must maintain a system which is always bootable. For instance, if
1092
you test a new kernel, you need to keep a working kernel in a
1093
different place. And, it would sometimes be very nice to even have a
1094
complete copy of a working system in a different partition or disk.
1097
You must direct GRUB to boot a working system when the new system
1098
fails. This is possible with the @dfn{fallback} system in GRUB.
1101
The former requirement is very specific to each OS, so this
1102
documentation does not cover that topic. It is better to consult some
1105
So let's see the GRUB part. There are two possibilities: one of them
1106
is quite simple but not very robust, and the other is a bit complex to
1107
set up but probably the best solution to make sure that your system
1108
can start as long as GRUB itself is bootable.
1111
* Booting once-only::
1112
* Booting fallback systems::
1116
@node Booting once-only
1117
@subsection Booting once-only
1119
You can teach GRUB to boot an entry only at next boot time. Suppose
1120
that your have an old kernel @file{old_kernel} and a new kernel
1121
@file{new_kernel}. You know that @file{old_kernel} can boot
1122
your system correctly, and you want to test @file{new_kernel}.
1124
To ensure that your system will go back to the old kernel even if the
1125
new kernel fails (e.g. it panics), you can specify that GRUB should
1126
try the new kernel only once and boot the old kernel after that.
1128
First, modify your configuration file. Here is an example:
1132
default saved # This is important!!!
1135
title the old kernel
1140
title the new kernel
1143
savedefault 0 # This is important!!!
1147
Note that this configuration file uses @samp{default saved}
1148
(@pxref{default}) at the head and @samp{savedefault 0}
1149
(@pxref{savedefault}) in the entry for the new kernel. This means
1150
that GRUB boots a saved entry by default, and booting the entry for the
1151
new kernel saves @samp{0} as the saved entry.
1153
With this configuration file, after all, GRUB always tries to boot the
1154
old kernel after it booted the new one, because @samp{0} is the entry
1155
of @code{the old kernel}.
1157
The next step is to tell GRUB to boot the new kernel at next boot
1158
time. For this, execute @command{grub-set-default} (@pxref{Invoking
1162
# @kbd{grub-set-default 1}
1165
This command sets the saved entry to @samp{1}, that is, to the new
1168
This method is useful, but still not very robust, because GRUB stops
1169
booting, if there is any error in the boot entry, such that the new
1170
kernel has an invalid executable format. Thus, it it even better to
1171
use the @dfn{fallback} mechanism of GRUB. Look at next subsection for
1175
@node Booting fallback systems
1176
@subsection Booting fallback systems
1178
GRUB supports a fallback mechanism of booting one or more other
1179
entries if a default boot entry fails. You can specify multiple
1180
fallback entries if you wish.
1182
Suppose that you have three systems, @samp{A}, @samp{B} and
1183
@samp{C}. @samp{A} is a system which you want to boot by
1184
default. @samp{B} is a backup system which is supposed to boot
1185
safely. @samp{C} is another backup system which is used in case where
1188
Then you may want GRUB to boot the first system which is bootable
1189
among @samp{A}, @samp{B} and @samp{C}. A configuration file can be
1190
written in this way:
1194
default saved # This is important!!!
1196
fallback 1 2 # This is important!!!
1201
savedefault fallback # This is important!!!
1206
savedefault fallback # This is important!!!
1215
Note that @samp{default saved} (@pxref{default}), @samp{fallback 1 2}
1216
and @samp{savedefault fallback} are used. GRUB will boot a saved entry
1217
by default and save a fallback entry as next boot entry with this
1220
When GRUB tries to boot @samp{A}, GRUB saves @samp{1} as next boot
1221
entry, because the command @command{fallback} specifies that @samp{1}
1222
is the first fallback entry. The entry @samp{1} is @samp{B}, so GRUB
1223
will try to boot @samp{B} at next boot time.
1225
Likewise, when GRUB tries to boot @samp{B}, GRUB saves @samp{2} as
1226
next boot entry, because @command{fallback} specifies @samp{2} as next
1227
fallback entry. This makes sure that GRUB will boot @samp{C} after
1230
It is noteworthy that GRUB uses fallback entries both when GRUB
1231
itself fails in booting an entry and when @samp{A} or @samp{B} fails
1232
in starting up your system. So this solution ensures that your system
1233
is started even if GRUB cannot find your kernel or if your kernel
1236
However, you need to run @command{grub-set-default} (@pxref{Invoking
1237
grub-set-default}) when @samp{A} starts correctly or you fix @samp{A}
1238
after it crashes, since GRUB always sets next boot entry to a fallback
1239
entry. You should run this command in a startup script such as
1240
@file{rc.local} to boot @samp{A} by default:
1243
# @kbd{grub-set-default 0}
1246
where @samp{0} is the number of the boot entry for the system
1249
If you want to see what is current default entry, you can look at the
1250
file @file{/boot/grub/default} (or @file{/grub/default} in
1251
some systems). Because this file is plain-text, you can just
1252
@command{cat} this file. But it is strongly recommended @strong{not to
1253
modify this file directly}, because GRUB may fail in saving a default
1254
entry in this file, if you change this file in an unintended
1255
manner. Therefore, you should use @command{grub-set-default} when you
1256
need to change the default entry.
1260
@chapter Configuration
1262
You've probably noticed that you need to type several commands to boot your
1263
OS. There's a solution to that - GRUB provides a menu interface
1264
(@pxref{Menu interface}) from which you can select an item (using arrow
1265
keys) that will do everything to boot an OS.
1267
To enable the menu, you need a configuration file,
1268
@file{menu.lst} under the boot directory. We'll analyze an example
1271
The file first contains some general settings, the menu interface
1272
related options. You can put these commands (@pxref{Menu-specific
1273
commands}) before any of the items (starting with @command{title}
1279
# Sample boot menu configuration file
1284
As you may have guessed, these lines are comments. Lines starting with a
1285
hash character (@samp{#}), and blank lines, are ignored by GRUB.
1289
# By default, boot the first entry.
1294
The first entry (here, counting starts with number zero, not one!) will
1295
be the default choice.
1299
# Boot automatically after 30 secs.
1304
As the comment says, GRUB will boot automatically in 30 seconds, unless
1305
interrupted with a keypress.
1309
# Fallback to the second entry.
1314
If, for any reason, the default entry doesn't work, fall back to the
1315
second one (this is rarely used, for obvious reasons).
1317
Note that the complete descriptions of these commands, which are menu
1318
interface specific, can be found in @ref{Menu-specific
1319
commands}. Other descriptions can be found in @ref{Commands}.
1321
Now, on to the actual OS definitions. You will see that each entry
1322
begins with a special command, @command{title} (@pxref{title}), and the
1323
action is described after it. Note that there is no command
1324
@command{boot} (@pxref{boot}) at the end of each item. That is because
1325
GRUB automatically executes @command{boot} if it loads other commands
1328
The argument for the command @command{title} is used to display a short
1329
title/description of the entry in the menu. Since @command{title}
1330
displays the argument as is, you can write basically anything there.
1334
# For booting GNU/Hurd
1337
kernel /boot/gnumach.gz root=hd0s1
1338
module /boot/serverboot.gz
1342
This boots GNU/Hurd from the first hard disk.
1346
# For booting GNU/Linux
1348
kernel (hd1,0)/vmlinuz root=/dev/hdb1
1352
This boots GNU/Linux, but from the second hard disk.
1356
# For booting Mach (getting kernel from floppy)
1357
title Utah Mach4 multiboot
1359
pause Insert the diskette now^G!!
1360
kernel (fd0)/boot/kernel root=hd0s3
1361
module (fd0)/boot/bootstrap
1365
This boots Mach with a kernel on a floppy, but the root filesystem at
1366
hd0s3. It also contains a @command{pause} line (@pxref{pause}), which
1367
will cause GRUB to display a prompt and delay, before actually executing
1368
the rest of the commands and booting.
1372
# For booting FreeBSD
1379
This item will boot FreeBSD kernel loaded from the @samp{a} partition of
1380
the third @sc{pc} slice of the first hard disk.
1388
# chainload OS/2 bootloader from the first sector
1390
# This is similar to "chainload", but loads a specific file
1391
#chainloader /boot/chain.os2
1395
This will boot OS/2, using a chain-loader (@pxref{Chain-loading}).
1399
# For booting Windows NT or Windows95
1400
title Windows NT / Windows 95 boot menu
1404
# For loading DOS if Windows NT is installed
1405
# chainload /bootsect.dos
1409
The same as the above, but for Windows.
1413
# For installing GRUB into the hard disk
1414
title Install GRUB into the hard disk
1420
This will just (re)install GRUB onto the hard disk.
1423
# Change the colors.
1424
title Change the colors
1425
color light-green/brown blink-red/blue
1428
In the last entry, the command @command{color} is used (@pxref{color}),
1429
to change the menu colors (try it!). This command is somewhat special,
1430
because it can be used both in the command-line and in the menu. GRUB
1431
has several such commands, see @ref{General commands}.
1433
We hope that you now understand how to use the basic features of
1434
GRUB. To learn more about GRUB, see the following chapters.
1438
@chapter Downloading OS images from a network
1440
Although GRUB is a disk-based boot loader, it does provide network
1441
support. To use the network support, you need to enable at least one
1442
network driver in the GRUB build process. For more information please
1443
see @file{netboot/README.netboot} in the source distribution.
1446
* General usage of network support::
1451
@node General usage of network support
1452
@section How to set up your network
1454
GRUB requires a file server and optionally a server that will assign an
1455
IP address to the machine on which GRUB is running. For the former, only
1456
TFTP is supported at the moment. The latter is either BOOTP, DHCP or a
1457
RARP server@footnote{RARP is not advised, since it cannot serve much
1458
information}. It is not necessary to run both the servers on one
1459
computer. How to configure these servers is beyond the scope of this
1460
document, so please refer to the manuals specific to those
1463
If you decided to use a server to assign an IP address, set up the
1464
server and run @command{bootp} (@pxref{bootp}), @command{dhcp}
1465
(@pxref{dhcp}) or @command{rarp} (@pxref{rarp}) for BOOTP, DHCP or RARP,
1466
respectively. Each command will show an assigned IP address, a netmask,
1467
an IP address for your TFTP server and a gateway. If any of the
1468
addresses is wrong or it causes an error, probably the configuration of
1469
your servers isn't set up properly.
1471
Otherwise, run @command{ifconfig}, like this:
1474
grub> @kbd{ifconfig --address=192.168.110.23 --server=192.168.110.14}
1477
You can also use @command{ifconfig} in conjuction with @command{bootp},
1478
@command{dhcp} or @command{rarp} (e.g. to reassign the server address
1479
manually). @xref{ifconfig}, for more details.
1481
Finally, download your OS images from your network. The network can be
1482
accessed using the network drive @samp{(nd)}. Everything else is very
1483
similar to the normal instructions (@pxref{Booting}).
1492
Address: 192.168.110.23 Netmask: 255.255.255.0
1493
Server: 192.168.110.14 Gateway: 192.168.110.1
1495
grub> @kbd{root (nd)}
1496
grub> @kbd{kernel /tftproot/gnumach.gz root=sd0s1}
1497
grub> @kbd{module /tftproot/serverboot.gz}
1504
@section Booting from a network
1506
It is sometimes very useful to boot from a network, especially when you
1507
use a machine which has no local disk. In this case, you need to obtain
1508
a kind of Net Boot @sc{rom}, such as a PXE @sc{rom} or a free software
1509
package like Etherboot. Such a Boot @sc{rom} first boots the machine,
1510
sets up the network card installed into the machine, and downloads a
1511
second stage boot image from the network. Then, the second image will
1512
try to boot an operating system actually from the network.
1514
GRUB provides two second stage images, @file{nbgrub} and
1515
@file{pxegrub} (@pxref{Images}). These images are the same as the
1516
normal Stage 2, except that they set up a network automatically, and try
1517
to load a configuration file from the network, if specified. The usage
1518
is very simple: If the machine has a PXE @sc{rom}, use
1519
@file{pxegrub}. If the machine has an NBI loader such as Etherboot, use
1520
@file{nbgrub}. There is no difference between them except their
1521
formats. Since the way to load a second stage image you want to use
1522
should be described in the manual on your Net Boot @sc{rom}, please
1523
refer to the manual, for more information.
1525
However, there is one thing specific to GRUB. Namely, how to specify a
1526
configuration file in a BOOTP/DHCP server. For now, GRUB uses the tag
1527
@samp{150}, to get the name of a configuration file. The following is an
1528
example with a BOOTP configuration:
1532
.allhost:hd=/tmp:bf=null:\
1533
:ds=145.71.35.1 145.71.32.1:\
1538
foo:ht=1:ha=63655d0334a7:ip=145.71.35.127:\
1541
:T150="(nd)/tftpboot/menu.lst.foo":
1545
Note that you should specify the drive name @code{(nd)} in the name of
1546
the configuration file. This is because you might change the root drive
1547
before downloading the configuration from the TFTP server when the
1548
preset menu feature is used (@pxref{Preset Menu}).
1550
See the manual of your BOOTP/DHCP server for more information. The
1551
exact syntax should differ a little from the example.
1554
@node Serial terminal
1555
@chapter Using GRUB via a serial line
1557
This chapter describes how to use the serial terminal support in GRUB.
1559
If you have many computers or computers with no display/keyboard, it
1560
could be very useful to control the computers through serial
1561
communications. To connect one computer with another via a serial line,
1562
you need to prepare a null-modem (cross) serial cable, and you may need
1563
to have multiport serial boards, if your computer doesn't have extra
1564
serial ports. In addition, a terminal emulator is also required, such as
1565
minicom. Refer to a manual of your operating system, for more
1568
As for GRUB, the instruction to set up a serial terminal is quite
1569
simple. First of all, make sure that you haven't specified the option
1570
@option{--disable-serial} to the configure script when you built your
1571
GRUB images. If you get them in binary form, probably they have serial
1572
terminal support already.
1574
Then, initialize your serial terminal after GRUB starts up. Here is an
1579
grub> @kbd{serial --unit=0 --speed=9600}
1580
grub> @kbd{terminal serial}
1584
The command @command{serial} initializes the serial unit 0 with the
1585
speed 9600bps. The serial unit 0 is usually called @samp{COM1}, so, if
1586
you want to use COM2, you must specify @samp{--unit=1} instead. This
1587
command accepts many other options, so please refer to @ref{serial},
1590
The command @command{terminal} (@pxref{terminal}) chooses which type of
1591
terminal you want to use. In the case above, the terminal will be a
1592
serial terminal, but you can also pass @code{console} to the command,
1593
as @samp{terminal serial console}. In this case, a terminal in which
1594
you press any key will be selected as a GRUB terminal.
1596
However, note that GRUB assumes that your terminal emulator is
1597
compatible with VT100 by default. This is true for most terminal
1598
emulators nowadays, but you should pass the option @option{--dumb} to
1599
the command if your terminal emulator is not VT100-compatible or
1600
implements few VT100 escape sequences. If you specify this option then
1601
GRUB provides you with an alternative menu interface, because the normal
1602
menu requires several fancy features of your terminal.
1606
@chapter Embedding a configuration file into GRUB
1608
GRUB supports a @dfn{preset menu} which is to be always loaded before
1609
starting. The preset menu feature is useful, for example, when your
1610
computer has no console but a serial cable. In this case, it is
1611
critical to set up the serial terminal as soon as possible, since you
1612
cannot see any message until the serial terminal begins to work. So it
1613
is good to run the commands @command{serial} (@pxref{serial}) and
1614
@command{terminal} (@pxref{terminal}) before anything else at the
1617
How the preset menu works is slightly complicated:
1621
GRUB checks if the preset menu feature is used, and loads the preset
1622
menu, if available. This includes running commands and reading boot
1623
entries, like an ordinary configuration file.
1626
GRUB checks if the configuration file is available. Note that this check
1627
is performed @strong{regardless of the existence of the preset
1628
menu}. The configuration file is loaded even if the preset menu was
1632
If the preset menu includes any boot entries, they are cleared when
1633
the configuration file is loaded. It doesn't matter whether the
1634
configuration file has any entries or no entry. The boot entries in the
1635
preset menu are used only when GRUB fails in loading the configuration
1639
To enable the preset menu feature, you must rebuild GRUB specifying a
1640
file to the configure script with the option
1641
@option{--enable-preset-menu}. The file has the same semantics as
1642
normal configuration files (@pxref{Configuration}).
1644
Another point you should take care is that the diskless support
1645
(@pxref{Diskless}) diverts the preset menu. Diskless images embed a
1646
preset menu to execute the command @command{bootp} (@pxref{bootp})
1647
automatically, unless you specify your own preset menu to the configure
1648
script. This means that you must put commands to initialize a network in
1649
the preset menu yourself, because diskless images don't set it up
1650
implicitly, when you use the preset menu explicitly.
1652
Therefore, a typical preset menu used with diskless support would be
1657
# Set up the serial terminal, first of all.
1658
serial --unit=0 --speed=19200
1659
terminal --timeout=0 serial
1661
# Initialize the network.
1668
@chapter Protecting your computer from cracking
1670
You may be interested in how to prevent ordinary users from doing
1671
whatever they like, if you share your computer with other people. So
1672
this chapter describes how to improve the security of GRUB.
1674
One thing which could be a security hole is that the user can do too
1675
many things with GRUB, because GRUB allows one to modify its configuration
1676
and run arbitrary commands at run-time. For example, the user can even
1677
read @file{/etc/passwd} in the command-line interface by the command
1678
@command{cat} (@pxref{cat}). So it is necessary to disable all the
1679
interactive operations.
1681
Thus, GRUB provides a @dfn{password} feature, so that only administrators
1682
can start the interactive operations (i.e. editing menu entries and
1683
entering the command-line interface). To use this feature, you need to
1684
run the command @command{password} in your configuration file
1685
(@pxref{password}), like this:
1688
password --md5 PASSWORD
1691
If this is specified, GRUB disallows any interactive control, until you
1692
press the key @key{p} and enter a correct password. The option
1693
@option{--md5} tells GRUB that @samp{PASSWORD} is in MD5 format. If it
1694
is omitted, GRUB assumes the @samp{PASSWORD} is in clear text.
1696
You can encrypt your password with the command @command{md5crypt}
1697
(@pxref{md5crypt}). For example, run the grub shell (@pxref{Invoking the
1698
grub shell}), and enter your password:
1703
Password: **********
1704
Encrypted: $1$U$JK7xFegdxWH6VuppCUSIb.
1708
Then, cut and paste the encrypted password to your configuration file.
1710
Also, you can specify an optional argument to @command{password}. See
1714
password PASSWORD /boot/grub/menu-admin.lst
1717
In this case, GRUB will load @file{/boot/grub/menu-admin.lst} as a
1718
configuration file when you enter the valid password.
1720
Another thing which may be dangerous is that any user can choose any
1721
menu entry. Usually, this wouldn't be problematic, but you might want to
1722
permit only administrators to run some of your menu entries, such as an
1723
entry for booting an insecure OS like DOS.
1725
GRUB provides the command @command{lock} (@pxref{lock}). This command
1726
always fails until you enter the valid password, so you can use it, like
1733
rootnoverify (hd0,1)
1739
You should insert @command{lock} right after @command{title}, because
1740
any user can execute commands in an entry until GRUB encounters
1743
You can also use the command @command{password} instead of
1744
@command{lock}. In this case the boot process will ask for the password
1745
and stop if it was entered incorrectly. Since the @command{password}
1746
takes its own @var{PASSWORD} argument this is useful if you want
1747
different passwords for different entries.
1751
@chapter GRUB image files
1753
GRUB consists of several images: two essential stages, optional stages
1754
called @dfn{Stage 1.5}, one image for bootable CD-ROM, and two network
1755
boot images. Here is a short overview of them. @xref{Internals}, for
1760
This is an essential image used for booting up GRUB. Usually, this is
1761
embedded in an MBR or the boot sector of a partition. Because a PC boot
1762
sector is 512 bytes, the size of this image is exactly 512 bytes.
1764
All @file{stage1} must do is to load Stage 2 or Stage 1.5 from a local
1765
disk. Because of the size restriction, @file{stage1} encodes the
1766
location of Stage 2 (or Stage 1.5) in a block list format, so it never
1767
understand any filesystem structure.
1770
This is the core image of GRUB. It does everything but booting up
1771
itself. Usually, this is put in a filesystem, but that is not required.
1777
@itemx minix_stage1_5
1778
@itemx reiserfs_stage1_5
1779
@itemx vstafs_stage1_5
1782
These are called @dfn{Stage 1.5}, because they serve as a bridge
1783
between @file{stage1} and @file{stage2}, that is to say, Stage 1.5 is
1784
loaded by Stage 1 and Stage 1.5 loads Stage 2. The difference between
1785
@file{stage1} and @file{*_stage1_5} is that the former doesn't
1786
understand any filesystem while the latter understands one filesystem
1787
(e.g. @file{e2fs_stage1_5} understands ext2fs). So you can move the
1788
Stage 2 image to another location safely, even after GRUB has been
1791
While Stage 2 cannot generally be embedded in a fixed area as the size
1792
is so large, Stage 1.5 can be installed into the area right after an MBR,
1793
or the boot loader area of a ReiserFS or a FFS.
1795
@item stage2_eltorito
1796
This is a boot image for CD-ROMs using the @dfn{no emulation mode} in
1797
El Torito specification. This is identical to Stage 2, except that
1798
this boots up without Stage 1 and sets up a special drive @samp{(cd)}.
1801
This is a network boot image for the Network Image Proposal used by some
1802
network boot loaders, such as Etherboot. This is mostly the same as
1803
Stage 2, but it also sets up a network and loads a configuration file
1807
This is another network boot image for the Preboot Execution Environment
1808
used by several Netboot ROMs. This is identical to @file{nbgrub}, except
1814
@chapter Filesystem syntax and semantics
1816
GRUB uses a special syntax for specifying disk drives which can be
1817
accessed by BIOS. Because of BIOS limitations, GRUB cannot distinguish
1818
between IDE, ESDI, SCSI, or others. You must know yourself which BIOS
1819
device is equivalent to which OS device. Normally, that will be clear if
1820
you see the files in a device or use the command @command{find}
1824
* Device syntax:: How to specify devices
1825
* File name syntax:: How to specify files
1826
* Block list syntax:: How to specify block lists
1831
@section How to specify devices
1833
The device syntax is like this:
1836
@code{(@var{device}[,@var{part-num}][,@var{bsd-subpart-letter}])}
1839
@samp{[]} means the parameter is optional. @var{device} should be
1840
either @samp{fd} or @samp{hd} followed by a digit, like @samp{fd0}.
1841
But you can also set @var{device} to a hexadecimal or a decimal number
1842
which is a BIOS drive number, so the following are equivalent:
1850
@var{part-num} represents the partition number of @var{device}, starting
1851
from zero for primary partitions and from four for extended partitions,
1852
and @var{bsd-subpart-letter} represents the BSD disklabel subpartition,
1853
such as @samp{a} or @samp{e}.
1855
A shortcut for specifying BSD subpartitions is
1856
@code{(@var{device},@var{bsd-subpart-letter})}, in this case, GRUB
1857
searches for the first PC partition containing a BSD disklabel, then
1858
finds the subpartition @var{bsd-subpart-letter}. Here is an example:
1864
The syntax @samp{(hd0)} represents using the entire disk (or the
1865
MBR when installing GRUB), while the syntax @samp{(hd0,0)}
1866
represents using the first partition of the disk (or the boot sector
1867
of the partition when installing GRUB).
1869
If you enabled the network support, the special drive, @samp{(nd)}, is
1870
also available. Before using the network drive, you must initialize the
1871
network. @xref{Network}, for more information.
1873
If you boot GRUB from a CD-ROM, @samp{(cd)} is available. @xref{Making
1874
a GRUB bootable CD-ROM}, for details.
1877
@node File name syntax
1878
@section How to specify files
1880
There are two ways to specify files, by @dfn{absolute file name} and by
1883
An absolute file name resembles a Unix absolute file name, using
1884
@samp{/} for the directory separator (not @samp{\} as in DOS). One
1885
example is @samp{(hd0,0)/boot/grub/menu.lst}. This means the file
1886
@file{/boot/grub/menu.lst} in the first partition of the first hard
1887
disk. If you omit the device name in an absolute file name, GRUB uses
1888
GRUB's @dfn{root device} implicitly. So if you set the root device to,
1889
say, @samp{(hd1,0)} by the command @command{root} (@pxref{root}), then
1890
@code{/boot/kernel} is the same as @code{(hd1,0)/boot/kernel}.
1893
@node Block list syntax
1894
@section How to specify block lists
1896
A block list is used for specifying a file that doesn't appear in the
1897
filesystem, like a chainloader. The syntax is
1898
@code{[@var{offset}]+@var{length}[,[@var{offset}]+@var{length}]@dots{}}.
1902
@code{0+100,200+1,300+300}
1905
This represents that GRUB should read blocks 0 through 99, block 200,
1906
and blocks 300 through 599. If you omit an offset, then GRUB assumes
1909
Like the file name syntax (@pxref{File name syntax}), if a blocklist
1910
does not contain a device name, then GRUB uses GRUB's @dfn{root
1911
device}. So @code{(hd0,1)+1} is the same as @code{+1} when the root
1912
device is @samp{(hd0,1)}.
1916
@chapter GRUB's user interface
1918
GRUB has both a simple menu interface for choosing preset entries from a
1919
configuration file, and a highly flexible command-line for performing
1920
any desired combination of boot commands.
1922
GRUB looks for its configuration file as soon as it is loaded. If one
1923
is found, then the full menu interface is activated using whatever
1924
entries were found in the file. If you choose the @dfn{command-line} menu
1925
option, or if the configuration file was not found, then GRUB drops to
1926
the command-line interface.
1929
* Command-line interface:: The flexible command-line interface
1930
* Menu interface:: The simple menu interface
1931
* Menu entry editor:: Editing a menu entry
1932
* Hidden menu interface:: The hidden menu interface
1936
@node Command-line interface
1937
@section The flexible command-line interface
1939
The command-line interface provides a prompt and after it an editable
1940
text area much like a command-line in Unix or DOS. Each command is
1941
immediately executed after it is entered@footnote{However, this
1942
behavior will be changed in the future version, in a user-invisible
1943
way.}. The commands (@pxref{Command-line and menu entry commands}) are a
1944
subset of those available in the configuration file, used with exactly
1947
Cursor movement and editing of the text on the line can be done via a
1948
subset of the functions available in the Bash shell:
1953
Move forward one character.
1957
Move back one character.
1961
Move to the start of the line.
1965
Move the the end of the line.
1969
Delete the character underneath the cursor.
1973
Delete the character to the left of the cursor.
1976
Kill the text from the current cursor position to the end of the line.
1979
Kill backward from the cursor to the beginning of the line.
1982
Yank the killed text back into the buffer at the cursor.
1986
Move up through the history list.
1990
Move down through the history list.
1993
When typing commands interactively, if the cursor is within or before
1994
the first word in the command-line, pressing the @key{TAB} key (or
1995
@key{C-i}) will display a listing of the available commands, and if the
1996
cursor is after the first word, the @kbd{@key{TAB}} will provide a
1997
completion listing of disks, partitions, and file names depending on the
1998
context. Note that to obtain a list of drives, one must open a
1999
parenthesis, as @command{root (}.
2001
Note that you cannot use the completion functionality in the TFTP
2002
filesystem. This is because TFTP doesn't support file name listing for
2006
@node Menu interface
2007
@section The simple menu interface
2009
The menu interface is quite easy to use. Its commands are both
2010
reasonably intuitive and described on screen.
2012
Basically, the menu interface provides a list of @dfn{boot entries} to
2013
the user to choose from. Use the arrow keys to select the entry of
2014
choice, then press @key{RET} to run it. An optional timeout is
2015
available to boot the default entry (the first one if not set), which is
2016
aborted by pressing any key.
2018
Commands are available to enter a bare command-line by pressing @key{c}
2019
(which operates exactly like the non-config-file version of GRUB, but
2020
allows one to return to the menu if desired by pressing @key{ESC}) or to
2021
edit any of the @dfn{boot entries} by pressing @key{e}.
2023
If you protect the menu interface with a password (@pxref{Security}),
2024
all you can do is choose an entry by pressing @key{RET}, or press
2025
@key{p} to enter the password.
2028
@node Menu entry editor
2029
@section Editing a menu entry
2031
The menu entry editor looks much like the main menu interface, but the
2032
lines in the menu are individual commands in the selected entry instead
2035
If an @key{ESC} is pressed in the editor, it aborts all the changes made
2036
to the configuration entry and returns to the main menu interface.
2038
When a particular line is selected, the editor places the user in a
2039
special version of the GRUB command-line to edit that line. When the
2040
user hits @key{RET}, GRUB replaces the line in question in the boot
2041
entry with the changes (unless it was aborted via @key{ESC},
2042
in which case the changes are thrown away).
2044
If you want to add a new line to the menu entry, press @key{o} if adding
2045
a line after the current line or press @key{O} if before the current
2048
To delete a line, hit the key @key{d}. Although GRUB unfortunately
2049
does not support @dfn{undo}, you can do almost the same thing by just
2050
returning to the main menu.
2053
@node Hidden menu interface
2054
@section The hidden menu interface
2056
When your terminal is dumb or you request GRUB to hide the menu
2057
interface explicitly with the command @command{hiddenmenu}
2058
(@pxref{hiddenmenu}), GRUB doesn't show the menu interface (@pxref{Menu
2059
interface}) and automatically boots the default entry, unless
2060
interrupted by pressing @key{ESC}.
2062
When you interrupt the timeout and your terminal is dumb, GRUB falls
2063
back to the command-line interface (@pxref{Command-line interface}).
2067
@chapter The list of available commands
2069
In this chapter, we list all commands that are available in GRUB.
2071
Commands belong to different groups. A few can only be used in
2072
the global section of the configuration file (or ``menu''); most
2073
of them can be entered on the command-line and can be used either
2074
anywhere in the menu or specifically in the menu entries.
2077
* Menu-specific commands::
2078
* General commands::
2079
* Command-line and menu entry commands::
2083
@node Menu-specific commands
2084
@section The list of commands for the menu only
2086
The semantics used in parsing the configuration file are the following:
2090
The menu-specific commands have to be used before any others.
2093
The files @emph{must} be in plain-text format.
2096
@samp{#} at the beginning of a line in a configuration file means it is
2100
Options are separated by spaces.
2103
All numbers can be either decimal or hexadecimal. A hexadecimal number
2104
must be preceded by @samp{0x}, and is case-insensitive.
2107
Extra options or text at the end of the line are ignored unless otherwise
2111
Unrecognized commands are added to the current entry, except before entries
2112
start, where they are ignored.
2115
These commands can only be used in the menu:
2118
* default:: Set the default entry
2119
* fallback:: Set the fallback entry
2120
* hiddenmenu:: Hide the menu interface
2121
* timeout:: Set the timeout
2122
* title:: Start a menu entry
2129
@deffn Command default num
2130
Set the default entry to the entry number @var{num}. Numbering starts
2131
from 0, and the entry number 0 is the default if the command is not
2134
You can specify @samp{saved} instead of a number. In this case, the
2135
default entry is the entry saved with the command
2136
@command{savedefault}. @xref{savedefault}, for more information.
2141
@subsection fallback
2143
@deffn Command fallback num...
2144
Go into unattended boot mode: if the default boot entry has any errors,
2145
instead of waiting for the user to do something, immediately start
2146
over using the @var{num} entry (same numbering as the @code{default}
2147
command (@pxref{default})). This obviously won't help if the machine was
2148
rebooted by a kernel that GRUB loaded. You can specify multiple
2149
fallback entry numbers.
2154
@subsection hiddenmenu
2156
@deffn Command hiddenmenu
2157
Don't display the menu. If the command is used, no menu will be
2158
displayed on the control terminal, and the default entry will be
2159
booted after the timeout expired. The user can still request the
2160
menu to be displayed by pressing @key{ESC} before the timeout
2161
expires. See also @ref{Hidden menu interface}.
2168
@deffn Command timeout sec
2169
Set a timeout, in @var{sec} seconds, before automatically booting the
2170
default entry (normally the first entry defined).
2177
@deffn Command title name @dots{}
2178
Start a new boot entry, and set its name to the contents of the rest of
2179
the line, starting with the first non-space character.
2183
@node General commands
2184
@section The list of general commands
2186
Commands usable anywhere in the menu and in the command-line.
2189
* bootp:: Initialize a network device via BOOTP
2190
* color:: Color the menu interface
2191
* device:: Specify a file as a drive
2192
* dhcp:: Initialize a network device via DHCP
2193
* hide:: Hide a partition
2194
* ifconfig:: Configure a network device manually
2195
* pager:: Change the state of the internal pager
2196
* partnew:: Make a primary partition
2197
* parttype:: Change the type of a partition
2198
* password:: Set a password for the menu interface
2199
* rarp:: Initialize a network device via RARP
2200
* serial:: Set up a serial device
2201
* setkey:: Configure the key map
2202
* terminal:: Choose a terminal
2203
* terminfo:: Define escape sequences for a terminal
2204
* tftpserver:: Specify a TFTP server
2205
* unhide:: Unhide a partition
2212
@deffn Command bootp [@option{--with-configfile}]
2213
Initialize a network device via the @dfn{BOOTP} protocol. This command
2214
is only available if GRUB is compiled with netboot support. See also
2217
If you specify @option{--with-configfile} to this command, GRUB will
2218
fetch and load a configuration file specified by your BOOTP server
2219
with the vendor tag @samp{150}.
2226
@deffn Command color normal [highlight]
2227
Change the menu colors. The color @var{normal} is used for most
2228
lines in the menu (@pxref{Menu interface}), and the color
2229
@var{highlight} is used to highlight the line where the cursor
2230
points. If you omit @var{highlight}, then the inverted color of
2231
@var{normal} is used for the highlighted line. The format of a color is
2232
@code{@var{foreground}/@var{background}}. @var{foreground} and
2233
@var{background} are symbolic color names. A symbolic color name must be
2261
@strong{These below can be specified only for the foreground.}
2288
But only the first eight names can be used for @var{background}. You can
2289
prefix @code{blink-} to @var{foreground} if you want a blinking
2292
This command can be used in the configuration file and on the command
2293
line, so you may write something like this in your configuration file:
2297
# Set default colors.
2298
color light-gray/blue black/light-gray
2300
# Change the colors.
2302
color magenta/blue black/magenta
2311
@deffn Command device drive file
2312
In the grub shell, specify the file @var{file} as the actual drive for a
2313
@sc{bios} drive @var{drive}. You can use this command to create a disk
2314
image, and/or to fix the drives guessed by GRUB when GRUB fails to
2315
determine them correctly, like this:
2319
grub> @kbd{device (fd0) /floppy-image}
2320
grub> @kbd{device (hd0) /dev/sd0}
2324
This command can be used only in the grub shell (@pxref{Invoking the
2332
@deffn Command dhcp [--with-configfile]
2333
Initialize a network device via the @dfn{DHCP} protocol. Currently,
2334
this command is just an alias for @command{bootp}, since the two
2335
protocols are very similar. This command is only available if GRUB is
2336
compiled with netboot support. See also @ref{Network}.
2338
If you specify @option{--with-configfile} to this command, GRUB will
2339
fetch and load a configuration file specified by your DHCP server
2340
with the vendor tag @samp{150}.
2347
@deffn Command hide partition
2348
Hide the partition @var{partition} by setting the @dfn{hidden} bit in
2349
its partition type code. This is useful only when booting DOS or Windows
2350
and multiple primary FAT partitions exist in one disk. See also
2356
@subsection ifconfig
2358
@deffn Command ifconfig [@option{--server=server}] [@option{--gateway=gateway}] [@option{--mask=mask}] [@option{--address=address}]
2359
Configure the IP address, the netmask, the gateway, and the server
2360
address of a network device manually. The values must be in dotted
2361
decimal format, like @samp{192.168.11.178}. The order of the options is
2362
not important. This command shows current network configuration, if no
2363
option is specified. See also @ref{Network}.
2370
@deffn Command pager [flag]
2371
Toggle or set the state of the internal pager. If @var{flag} is
2372
@samp{on}, the internal pager is enabled. If @var{flag} is @samp{off},
2373
it is disabled. If no argument is given, the state is toggled.
2380
@deffn Command partnew part type from len
2381
Create a new primary partition. @var{part} is a partition specification
2382
in GRUB syntax (@pxref{Naming convention}); @var{type} is the partition
2383
type and must be a number in the range @code{0-0xff}; @var{from} is
2384
the starting address and @var{len} is the length, both in sector units.
2389
@subsection parttype
2391
@deffn Command parttype part type
2392
Change the type of an existing partition. @var{part} is a partition
2393
specification in GRUB syntax (@pxref{Naming convention}); @var{type}
2394
is the new partition type and must be a number in the range 0-0xff.
2399
@subsection password
2401
@deffn Command password [@option{--md5}] passwd [new-config-file]
2402
If used in the first section of a menu file, disable all interactive
2403
editing control (menu entry editor and command-line) and entries
2404
protected by the command @command{lock}. If the password @var{passwd} is
2405
entered, it loads the @var{new-config-file} as a new config file and
2406
restarts the GRUB Stage 2, if @var{new-config-file} is
2407
specified. Otherwise, GRUB will just unlock the privileged instructions.
2408
You can also use this command in the script section, in which case it
2409
will ask for the password, before continuing. The option
2410
@option{--md5} tells GRUB that @var{passwd} is encrypted with
2411
@command{md5crypt} (@pxref{md5crypt}).
2419
Initialize a network device via the @dfn{RARP} protocol. This command
2420
is only available if GRUB is compiled with netboot support. See also
2428
@deffn Command serial [@option{--unit=unit}] [@option{--port=port}] [@option{--speed=speed}] [@option{--word=word}] [@option{--parity=parity}] [@option{--stop=stop}] [@option{--device=dev}]
2429
Initialize a serial device. @var{unit} is a number in the range 0-3
2430
specifying which serial port to use; default is 0, which corresponds to
2431
the port often called COM1. @var{port} is the I/O port where the UART
2432
is to be found; if specified it takes precedence over @var{unit}.
2433
@var{speed} is the transmission speed; default is 9600. @var{word} and
2434
@var{stop} are the number of data bits and stop bits. Data bits must
2435
be in the range 5-8 and stop bits must be 1 or 2. Default is 8 data
2436
bits and one stop bit. @var{parity} is one of @samp{no}, @samp{odd},
2437
@samp{even} and defaults to @samp{no}. The option @option{--device}
2438
can only be used in the grub shell and is used to specify the
2439
tty device to be used in the host operating system (@pxref{Invoking the
2442
The serial port is not used as a communication channel unless the
2443
@command{terminal} command is used (@pxref{terminal}).
2445
This command is only available if GRUB is compiled with serial
2446
support. See also @ref{Serial terminal}.
2453
@deffn Command setkey [to_key from_key]
2454
Change the keyboard map. The key @var{from_key} is mapped to the key
2455
@var{to_key}. If no argument is specified, reset key mappings. Note that
2456
this command @emph{does not} exchange the keys. If you want to exchange
2457
the keys, run this command again with the arguments exchanged, like this:
2460
grub> @kbd{setkey capslock control}
2461
grub> @kbd{setkey control capslock}
2464
A key must be an alphabet letter, a digit, or one of these symbols:
2465
@samp{escape}, @samp{exclam}, @samp{at}, @samp{numbersign},
2466
@samp{dollar}, @samp{percent}, @samp{caret}, @samp{ampersand},
2467
@samp{asterisk}, @samp{parenleft}, @samp{parenright}, @samp{minus},
2468
@samp{underscore}, @samp{equal}, @samp{plus}, @samp{backspace},
2469
@samp{tab}, @samp{bracketleft}, @samp{braceleft}, @samp{bracketright},
2470
@samp{braceright}, @samp{enter}, @samp{control}, @samp{semicolon},
2471
@samp{colon}, @samp{quote}, @samp{doublequote}, @samp{backquote},
2472
@samp{tilde}, @samp{shift}, @samp{backslash}, @samp{bar}, @samp{comma},
2473
@samp{less}, @samp{period}, @samp{greater}, @samp{slash},
2474
@samp{question}, @samp{alt}, @samp{space}, @samp{capslock}, @samp{FX}
2475
(@samp{X} is a digit), and @samp{delete}. This table describes to which
2476
character each of the symbols corresponds:
2582
@subsection terminal
2584
@deffn Command terminal [@option{--dumb}] [@option{--no-echo}] [@option{--no-edit}] [@option{--timeout=secs}] [@option{--lines=lines}] [@option{--silent}] [@option{console}] [@option{serial}] [@option{hercules}]
2585
Select a terminal for user interaction. The terminal is assumed to be
2586
VT100-compatible unless @option{--dumb} is specified. If both
2587
@option{console} and @option{serial} are specified, then GRUB will use
2588
the one where a key is entered first or the first when the timeout
2589
expires. If neither are specified, the current setting is
2590
reported. This command is only available if GRUB is compiled with serial
2591
support. See also @ref{Serial terminal}.
2593
This may not make sense for most users, but GRUB supports Hercules
2594
console as well. Hercules console is usable like the ordinary console,
2595
and the usage is quite similar to that for serial terminals: specify
2596
@option{hercules} as the argument.
2598
The option @option{--lines} defines the number of lines in your
2599
terminal, and it is used for the internal pager function. If you don't
2600
specify this option, the number is assumed as 24.
2602
The option @option{--silent} suppresses the message to prompt you to
2603
hit any key. This might be useful if your system has no terminal
2606
The option @option{--no-echo} has GRUB not to echo back input
2607
characters. This implies the option @option{--no-edit}.
2609
The option @option{--no-edit} disables the BASH-like editing feature.
2614
@subsection terminfo
2616
@deffn Command terminfo @option{--name=name} @option{--cursor-address=seq} [@option{--clear-screen=seq}] [@option{--enter-standout-mode=seq}] [@option{--exit-standout-mode=seq}]
2617
Define the capabilities of your terminal. Use this command to define
2618
escape sequences, if it is not vt100-compatible. You may use @samp{\e}
2619
for @key{ESC} and @samp{^X} for a control character.
2621
You can use the utility @command{grub-terminfo} to generate
2622
appropriate arguments to this command. @xref{Invoking grub-terminfo}.
2624
If no option is specified, the current settings are printed.
2629
@subsection tftpserver
2631
@deffn Command tftpserver ipaddr
2632
@strong{Caution:} This command exists only for backward
2633
compatibility. Use @command{ifconfig} (@pxref{ifconfig}) instead.
2635
Override a TFTP server address returned by a BOOTP/DHCP/RARP server. The
2636
argument @var{ipaddr} must be in dotted decimal format, like
2637
@samp{192.168.0.15}. This command is only available if GRUB is compiled
2638
with netboot support. See also @ref{Network}.
2645
@deffn Command unhide partition
2646
Unhide the partition @var{partition} by clearing the @dfn{hidden} bit in
2647
its partition type code. This is useful only when booting DOS or Windows
2648
and multiple primary partitions exist on one disk. See also
2653
@node Command-line and menu entry commands
2654
@section The list of command-line and menu entry commands
2656
These commands are usable in the command-line and in menu entries. If
2657
you forget a command, you can run the command @command{help}
2661
* blocklist:: Get the block list notation of a file
2662
* boot:: Start up your operating system
2663
* cat:: Show the contents of a file
2664
* chainloader:: Chain-load another boot loader
2665
* cmp:: Compare two files
2666
* configfile:: Load a configuration file
2667
* debug:: Toggle the debug flag
2668
* displayapm:: Display APM information
2669
* displaymem:: Display memory configuration
2670
* embed:: Embed Stage 1.5
2671
* find:: Find a file
2672
* fstest:: Test a filesystem
2673
* geometry:: Manipulate the geometry of a drive
2674
* halt:: Shut down your computer
2675
* help:: Show help messages
2676
* impsprobe:: Probe SMP
2677
* initrd:: Load an initrd
2678
* install:: Install GRUB
2679
* ioprobe:: Probe I/O ports used for a drive
2680
* kernel:: Load a kernel
2681
* lock:: Lock a menu entry
2682
* makeactive:: Make a partition active
2683
* map:: Map a drive to another
2684
* md5crypt:: Encrypt a password in MD5 format
2685
* module:: Load a module
2686
* modulenounzip:: Load a module without decompression
2687
* pause:: Wait for a key press
2688
* quit:: Exit from the grub shell
2689
* reboot:: Reboot your computer
2690
* read:: Read data from memory
2691
* root:: Set GRUB's root device
2692
* rootnoverify:: Set GRUB's root device without mounting
2693
* savedefault:: Save current entry as the default entry
2694
* setup:: Set up GRUB's installation automatically
2695
* testload:: Load a file for testing a filesystem
2696
* testvbe:: Test VESA BIOS EXTENSION
2697
* uppermem:: Set the upper memory size
2698
* vbeprobe:: Probe VESA BIOS EXTENSION
2703
@subsection blocklist
2705
@deffn Command blocklist file
2706
Print the block list notation of the file @var{file}. @xref{Block list
2715
Boot the OS or chain-loader which has been loaded. Only necessary if
2716
running the fully interactive command-line (it is implicit at the end of
2724
@deffn Command cat file
2725
Display the contents of the file @var{file}. This command may be useful
2726
to remind you of your OS's root partition:
2729
grub> @kbd{cat /etc/fstab}
2735
@subsection chainloader
2737
@deffn Command chainloader [@option{--force}] file
2738
Load @var{file} as a chain-loader. Like any other file loaded by the
2739
filesystem code, it can use the blocklist notation to grab the first
2740
sector of the current partition with @samp{+1}. If you specify the
2741
option @option{--force}, then load @var{file} forcibly, whether it has a
2742
correct signature or not. This is required when you want to load a
2743
defective boot loader, such as SCO UnixWare 7.1 (@pxref{SCO UnixWare}).
2750
@deffn Command cmp file1 file2
2751
Compare the file @var{file1} with the file @var{file2}. If they differ
2752
in size, print the sizes like this:
2755
Differ in size: 0x1234 [foo], 0x4321 [bar]
2758
If the sizes are equal but the bytes at an offset differ, then print the
2762
Differ at the offset 777: 0xbe [foo], 0xef [bar]
2765
If they are completely identical, nothing will be printed.
2770
@subsection configfile
2772
@deffn Command configfile file
2773
Load @var{file} as a configuration file.
2780
@deffn Command debug
2781
Toggle debug mode (by default it is off). When debug mode is on, some
2782
extra messages are printed to show disk activity. This global debug flag
2783
is mainly useful for GRUB developers when testing new code.
2788
@subsection displayapm
2790
@deffn Command displayapm
2791
Display APM BIOS information.
2796
@subsection displaymem
2798
@deffn Command displaymem
2799
Display what GRUB thinks the system address space map of the machine is,
2800
including all regions of physical @sc{ram} installed. GRUB's
2801
@dfn{upper/lower memory} display uses the standard BIOS interface for
2802
the available memory in the first megabyte, or @dfn{lower memory}, and a
2803
synthesized number from various BIOS interfaces of the memory starting
2804
at 1MB and going up to the first chipset hole for @dfn{upper memory}
2805
(the standard PC @dfn{upper memory} interface is limited to reporting a
2813
@deffn Command embed stage1_5 device
2814
Embed the Stage 1.5 @var{stage1_5} in the sectors after the MBR if
2815
@var{device} is a drive, or in the @dfn{boot loader} area if @var{device}
2816
is a FFS partition or a ReiserFS partition.@footnote{The latter feature
2817
has not been implemented yet.} Print the number of sectors which
2818
@var{stage1_5} occupies, if successful.
2820
Usually, you don't need to run this command directly. @xref{setup}.
2827
@deffn Command find filename
2828
Search for the file name @var{filename} in all mountable partitions
2829
and print the list of the devices which contain the file. The file
2830
name @var{filename} should be an absolute file name like
2831
@code{/boot/grub/stage1}.
2838
@deffn Command fstest
2839
Toggle filesystem test mode.
2840
Filesystem test mode, when turned on, prints out data corresponding to
2841
all the device reads and what values are being sent to the low-level
2842
routines. The format is @samp{<@var{partition-offset-sector},
2843
@var{byte-offset}, @var{byte-length}>} for high-level reads inside a
2844
partition, and @samp{[@var{disk-offset-sector}]} for low-level sector
2845
requests from the disk.
2846
Filesystem test mode is turned off by any use of the @command{install}
2847
(@pxref{install}) or @command{testload} (@pxref{testload}) commands.
2852
@subsection geometry
2854
@deffn Command geometry drive [cylinder head sector [total_sector]]
2855
Print the information for the drive @var{drive}. In the grub shell, you
2856
can set the geometry of the drive arbitrarily. The number of
2857
cylinders, the number of heads, the number of sectors and the number of
2858
total sectors are set to CYLINDER, HEAD, SECTOR and TOTAL_SECTOR,
2859
respectively. If you omit TOTAL_SECTOR, then it will be calculated
2860
based on the C/H/S values automatically.
2867
@deffn Command halt @option{--no-apm}
2868
The command halts the computer. If the @option{--no-apm} option
2869
is specified, no APM BIOS call is performed. Otherwise, the computer
2870
is shut down using APM.
2877
@deffn Command help @option{--all} [pattern @dots{}]
2878
Display helpful information about builtin commands. If you do not
2879
specify @var{pattern}, this command shows short descriptions of most of
2880
available commands. If you specify the option @option{--all} to this
2881
command, short descriptions of rarely used commands (such as
2882
@ref{testload}) are displayed as well.
2884
If you specify any @var{patterns}, it displays longer information
2885
about each of the commands which match those @var{patterns}.
2890
@subsection impsprobe
2892
@deffn Command impsprobe
2893
Probe the Intel Multiprocessor Specification 1.1 or 1.4 configuration
2894
table and boot the various CPUs which are found into a tight loop. This
2895
command can be used only in the Stage 2, but not in the grub shell.
2902
@deffn Command initrd file @dots{}
2903
Load an initial ramdisk for a Linux format boot image and set the
2904
appropriate parameters in the Linux setup area in memory. See also
2912
@deffn Command install [@option{--force-lba}] [@option{--stage2=os_stage2_file}] stage1_file [@option{d}] dest_dev stage2_file [addr] [@option{p}] [config_file] [real_config_file]
2913
This command is fairly complex, and you should not use this command
2914
unless you are familiar with GRUB. Use @command{setup} (@pxref{setup})
2917
In short, it will perform a full install presuming the Stage 2 or Stage
2918
1.5@footnote{They're loaded the same way, so we will refer to the Stage
2919
1.5 as a Stage 2 from now on.} is in its final install location.
2921
In slightly more detail, it will load @var{stage1_file}, validate that
2922
it is a GRUB Stage 1 of the right version number, install in it a
2923
blocklist for loading @var{stage2_file} as a Stage 2. If the option
2924
@option{d} is present, the Stage 1 will always look for the actual
2925
disk @var{stage2_file} was installed on, rather than using the booting
2926
drive. The Stage 2 will be loaded at address @var{addr}, which must be
2927
@samp{0x8000} for a true Stage 2, and @samp{0x2000} for a Stage 1.5. If
2928
@var{addr} is not present, GRUB will determine the address
2929
automatically. It then writes the completed Stage 1 to the first block
2930
of the device @var{dest_dev}. If the options @option{p} or
2931
@var{config_file} are present, then it reads the first block of stage2,
2932
modifies it with the values of the partition @var{stage2_file} was found
2933
on (for @option{p}) or places the string @var{config_file} into the area
2934
telling the stage2 where to look for a configuration file at boot
2935
time. Likewise, if @var{real_config_file} is present and
2936
@var{stage2_file} is a Stage 1.5, then the Stage 2 @var{config_file} is
2937
patched with the configuration file name @var{real_config_file}. This
2938
command preserves the DOS BPB (and for hard disks, the partition table)
2939
of the sector the Stage 1 is to be installed into.
2941
@strong{Caution:} Several buggy BIOSes don't pass a booting drive
2942
properly when booting from a hard disk drive. Therefore, you will
2943
unfortunately have to specify the option @option{d}, whether your
2944
Stage2 resides at the booting drive or not, if you have such a
2945
BIOS. We know these are defective in this way:
2949
Fujitsu LifeBook 400 BIOS version 31J0103A
2952
HP Vectra XU 6/200 BIOS version GG.06.11
2955
@strong{Caution2:} A number of BIOSes don't return a correct LBA support
2956
bitmap even if they do have the support. So GRUB provides a solution to
2957
ignore the wrong bitmap, that is, the option @option{--force-lba}. Don't
2958
use this option if you know that your BIOS doesn't have LBA support.
2960
@strong{Caution3:} You must specify the option @option{--stage2} in the
2961
grub shell, if you cannot unmount the filesystem where your stage2 file
2962
resides. The argument should be the file name in your operating system.
2969
@deffn Command ioprobe drive
2970
Probe I/O ports used for the drive @var{drive}. This command will list
2971
the I/O ports on the screen. For technical information,
2979
@deffn Command kernel [@option{--type=type}] [@option{--no-mem-option}] file @dots{}
2980
Attempt to load the primary boot image (Multiboot a.out or @sc{elf},
2981
Linux zImage or bzImage, FreeBSD a.out, NetBSD a.out, etc.) from
2982
@var{file}. The rest of the line is passed verbatim as the @dfn{kernel
2983
command-line}. Any modules must be reloaded after using this command.
2985
This command also accepts the option @option{--type} so that you can
2986
specify the kernel type of @var{file} explicitly. The argument
2987
@var{type} must be one of these: @samp{netbsd}, @samp{freebsd},
2988
@samp{openbsd}, @samp{linux}, @samp{biglinux}, and
2989
@samp{multiboot}. However, you need to specify it only if you want to
2990
load a NetBSD @sc{elf} kernel, because GRUB can automatically determine
2991
a kernel type in the other cases, quite safely.
2993
The option @option{--no-mem-option} is effective only for Linux. If the
2994
option is specified, GRUB doesn't pass the option @option{mem=} to the
2995
kernel. This option is implied for Linux kernels 2.4.18 and newer.
3003
Prevent normal users from executing arbitrary menu entries. You must use
3004
the command @command{password} if you really want this command to be
3005
useful (@pxref{password}).
3007
This command is used in a menu, as shown in this example:
3011
title This entry is too dangerous to be executed by normal users
3014
kernel /no-security-os
3018
See also @ref{Security}.
3023
@subsection makeactive
3025
@deffn Command makeactive
3026
Set the active partition on the root disk to GRUB's root device.
3027
This command is limited to @emph{primary} PC partitions on a hard disk.
3034
@deffn Command map to_drive from_drive
3035
Map the drive @var{from_drive} to the drive @var{to_drive}. This is
3036
necessary when you chain-load some operating systems, such as DOS, if
3037
such an OS resides at a non-first drive. Here is an example:
3041
grub> @kbd{map (hd0) (hd1)}
3042
grub> @kbd{map (hd1) (hd0)}
3046
The example exchanges the order between the first hard disk and the
3047
second hard disk. See also @ref{DOS/Windows}.
3052
@subsection md5crypt
3054
@deffn Command md5crypt
3055
Prompt to enter a password, and encrypt it in MD5 format. The encrypted
3056
password can be used with the command @command{password}
3057
(@pxref{password}). See also @ref{Security}.
3064
@deffn Command module file @dots{}
3065
Load a boot module @var{file} for a Multiboot format boot image (no
3066
interpretation of the file contents are made, so the user of this
3067
command must know what the kernel in question expects). The rest of the
3068
line is passed as the @dfn{module command-line}, like the
3069
@command{kernel} command. You must load a Multiboot kernel image before
3070
loading any module. See also @ref{modulenounzip}.
3075
@subsection modulenounzip
3077
@deffn Command modulenounzip file @dots{}
3078
The same as @command{module} (@pxref{module}), except that automatic
3079
decompression is disabled.
3086
@deffn Command pause message @dots{}
3087
Print the @var{message}, then wait until a key is pressed. Note that
3088
placing @key{^G} (ASCII code 7) in the message will cause the speaker to
3089
emit the standard beep sound, which is useful when prompting the user to
3098
Exit from the grub shell @command{grub} (@pxref{Invoking the grub
3099
shell}). This command can be used only in the grub shell.
3106
@deffn Command reboot
3107
Reboot the computer.
3114
@deffn Command read addr
3115
Read a 32-bit value from memory at address @var{addr} and display it in
3123
@deffn Command root device [hdbias]
3124
Set the current @dfn{root device} to the device @var{device}, then
3125
attempt to mount it to get the partition size (for passing the partition
3126
descriptor in @code{ES:ESI}, used by some chain-loaded boot loaders), the
3127
BSD drive-type (for booting BSD kernels using their native boot format),
3128
and correctly determine the PC partition where a BSD sub-partition is
3129
located. The optional @var{hdbias} parameter is a number to tell a BSD
3130
kernel how many BIOS drive numbers are on controllers before the current
3131
one. For example, if there is an IDE disk and a SCSI disk, and your
3132
FreeBSD root partition is on the SCSI disk, then use a @samp{1} for
3135
See also @ref{rootnoverify}.
3140
@subsection rootnoverify
3142
@deffn Command rootnoverify device [hdbias]
3143
Similar to @command{root} (@pxref{root}), but don't attempt to mount the
3144
partition. This is useful for when an OS is outside of the area of the
3145
disk that GRUB can read, but setting the correct root device is still
3146
desired. Note that the items mentioned in @command{root} above which
3147
derived from attempting the mount will @emph{not} work correctly.
3152
@subsection savedefault
3154
@deffn Command savedefault num
3155
Save the current menu entry or @var{num} if specified as a default
3156
entry. Here is an example:
3165
kernel /boot/vmlinuz root=/dev/sda1 vga=ext
3176
With this configuration, GRUB will choose the entry booted previously as
3179
You can specify @samp{fallback} instead of a number. Then, next
3180
fallback entry is saved. Next fallback entry is chosen from fallback
3181
entries. Normally, this will be the first entry in fallback ones.
3183
See also @ref{default} and @ref{Invoking grub-set-default}.
3190
@deffn Command setup [@option{--force-lba}] [@option{--stage2=os_stage2_file}] [@option{--prefix=dir}] install_device [image_device]
3191
Set up the installation of GRUB automatically. This command uses the
3192
more flexible command @command{install} (@pxref{install}) in the backend
3193
and installs GRUB into the device @var{install_device}. If
3194
@var{image_device} is specified, then find the GRUB images
3195
(@pxref{Images}) in the device @var{image_device}, otherwise use the
3196
current @dfn{root device}, which can be set by the command
3197
@command{root}. If @var{install_device} is a hard disk, then embed a
3198
Stage 1.5 in the disk if possible.
3200
The option @option{--prefix} specifies the directory under which GRUB
3201
images are put. If it is not specified, GRUB automatically searches them
3202
in @file{/boot/grub} and @file{/grub}.
3204
The options @option{--force-lba} and @option{--stage2} are just passed
3205
to @command{install} if specified. @xref{install}, for more
3211
@subsection testload
3213
@deffn Command testload file
3214
Read the entire contents of @var{file} in several different ways and
3215
compare them, to test the filesystem code. The output is somewhat
3216
cryptic, but if no errors are reported and the final @samp{i=@var{X},
3217
filepos=@var{Y}} reading has @var{X} and @var{Y} equal, then it is
3218
definitely consistent, and very likely works correctly subject to a
3219
consistent offset error. If this test succeeds, then a good next step is
3220
to try loading a kernel.
3227
@deffn Command testvbe mode
3228
Test the VESA BIOS EXTENSION mode @var{mode}. This command will switch
3229
your video card to the graphics mode, and show an endless animation. Hit
3230
any key to return. See also @ref{vbeprobe}.
3235
@subsection uppermem
3237
@deffn Command uppermem kbytes
3238
Force GRUB to assume that only @var{kbytes} kilobytes of upper memory
3239
are installed. Any system address range maps are discarded.
3241
@strong{Caution:} This should be used with great caution, and should
3242
only be necessary on some old machines. GRUB's BIOS probe can pick up
3243
all @sc{ram} on all new machines the author has ever heard of. It can
3244
also be used for debugging purposes to lie to an OS.
3249
@subsection vbeprobe
3251
@deffn Command vbeprobe [mode]
3252
Probe VESA BIOS EXTENSION information. If the mode @var{mode} is
3253
specified, show only the information about @var{mode}. Otherwise, this
3254
command lists up available VBE modes on the screen. See also
3259
@node Troubleshooting
3260
@chapter Error messages reported by GRUB
3262
This chapter describes error messages reported by GRUB when you
3263
encounter trouble. @xref{Invoking the grub shell}, if your problem is
3264
specific to the grub shell.
3267
* Stage1 errors:: Errors reported by the Stage 1
3268
* Stage1.5 errors:: Errors reported by the Stage 1.5
3269
* Stage2 errors:: Errors reported by the Stage 2
3274
@section Errors reported by the Stage 1
3276
The general way that the Stage 1 handles errors is to print an error
3277
string and then halt. Pressing @kbd{@key{CTRL}-@key{ALT}-@key{DEL}} will
3280
The following is a comprehensive list of error messages for the Stage 1:
3283
@item Hard Disk Error
3284
The stage2 or stage1.5 is being read from a hard disk, and the attempt
3285
to determine the size and geometry of the hard disk failed.
3288
The stage2 or stage1.5 is being read from a floppy disk, and the attempt
3289
to determine the size and geometry of the floppy disk failed. It's listed
3290
as a separate error since the probe sequence is different than for hard
3294
A disk read error happened while trying to read the stage2 or stage1.5.
3297
The location of the stage2 or stage1.5 is not in the portion of the disk
3298
supported directly by the BIOS read calls. This could occur because the
3299
BIOS translated geometry has been changed by the user or the disk is
3300
moved to another machine or controller after installation, or GRUB was
3301
not installed using itself (if it was, the Stage 2 version of this error
3302
would have been seen during that process and it would not have completed
3307
@node Stage1.5 errors
3308
@section Errors reported by the Stage 1.5
3310
The general way that the Stage 1.5 handles errors is to print an error
3311
number in the form @code{Error @var{num}} and then halt. Pressing
3312
@kbd{@key{CTRL}-@key{ALT}-@key{DEL}} will reboot.
3314
The error numbers correspond to the errors reported by Stage
3315
2. @xref{Stage2 errors}.
3319
@section Errors reported by the Stage 2
3321
The general way that the Stage 2 handles errors is to abort the
3322
operation in question, print an error string, then (if possible) either
3323
continue based on the fact that an error occurred or wait for the user to
3324
deal with the error.
3326
The following is a comprehensive list of error messages for the Stage 2
3327
(error numbers for the Stage 1.5 are listed before the colon in each
3331
@item 1 : Filename must be either an absolute filename or blocklist
3332
This error is returned if a file name is requested which doesn't fit the
3333
syntax/rules listed in the @ref{Filesystem}.
3335
@item 2 : Bad file or directory type
3336
This error is returned if a file requested is not a regular file, but
3337
something like a symbolic link, directory, or FIFO.
3339
@item 3 : Bad or corrupt data while decompressing file
3340
This error is returned if the run-length decompression code gets an
3341
internal error. This is usually from a corrupt file.
3343
@item 4 : Bad or incompatible header in compressed file
3344
This error is returned if the file header for a supposedly compressed
3347
@item 5 : Partition table invalid or corrupt
3348
This error is returned if the sanity checks on the integrity of the
3349
partition table fail. This is a bad sign.
3351
@item 6 : Mismatched or corrupt version of stage1/stage2
3352
This error is returned if the install command points to incompatible
3353
or corrupt versions of the stage1 or stage2. It can't detect corruption
3354
in general, but this is a sanity check on the version numbers, which
3357
@item 7 : Loading below 1MB is not supported
3358
This error is returned if the lowest address in a kernel is below the
3359
1MB boundary. The Linux zImage format is a special case and can be
3360
handled since it has a fixed loading address and maximum size.
3362
@item 8 : Kernel must be loaded before booting
3363
This error is returned if GRUB is told to execute the boot sequence
3364
without having a kernel to start.
3366
@item 9 : Unknown boot failure
3367
This error is returned if the boot attempt did not succeed for reasons
3370
@item 10 : Unsupported Multiboot features requested
3371
This error is returned when the Multiboot features word in the Multiboot
3372
header requires a feature that is not recognized. The point of this is
3373
that the kernel requires special handling which GRUB is probably
3376
@item 11 : Unrecognized device string
3377
This error is returned if a device string was expected, and the string
3378
encountered didn't fit the syntax/rules listed in the @ref{Filesystem}.
3380
@item 12 : Invalid device requested
3381
This error is returned if a device string is recognizable but does not
3382
fall under the other device errors.
3384
@item 13 : Invalid or unsupported executable format
3385
This error is returned if the kernel image being loaded is not
3386
recognized as Multiboot or one of the supported native formats (Linux
3387
zImage or bzImage, FreeBSD, or NetBSD).
3389
@item 14 : Filesystem compatibility error, cannot read whole file
3390
Some of the filesystem reading code in GRUB has limits on the length of
3391
the files it can read. This error is returned when the user runs into
3394
@item 15 : File not found
3395
This error is returned if the specified file name cannot be found, but
3396
everything else (like the disk/partition info) is OK.
3398
@item 16 : Inconsistent filesystem structure
3399
This error is returned by the filesystem code to denote an internal
3400
error caused by the sanity checks of the filesystem structure on disk
3401
not matching what it expects. This is usually caused by a corrupt
3402
filesystem or bugs in the code handling it in GRUB.
3404
@item 17 : Cannot mount selected partition
3405
This error is returned if the partition requested exists, but the
3406
filesystem type cannot be recognized by GRUB.
3408
@item 18 : Selected cylinder exceeds maximum supported by BIOS
3409
This error is returned when a read is attempted at a linear block
3410
address beyond the end of the BIOS translated area. This generally
3411
happens if your disk is larger than the BIOS can handle (512MB for
3412
(E)IDE disks on older machines or larger than 8GB in general).
3414
@item 19 : Linux kernel must be loaded before initrd
3415
This error is returned if the initrd command is used before loading a
3418
@item 20 : Multiboot kernel must be loaded before modules
3419
This error is returned if the module load command is used before loading
3420
a Multiboot kernel. It only makes sense in this case anyway, as GRUB has
3421
no idea how to communicate the presence of such modules to a
3422
non-Multiboot-aware kernel.
3424
@item 21 : Selected disk does not exist
3425
This error is returned if the device part of a device- or full file name
3426
refers to a disk or BIOS device that is not present or not recognized by
3427
the BIOS in the system.
3429
@item 22 : No such partition
3430
This error is returned if a partition is requested in the device part of
3431
a device- or full file name which isn't on the selected disk.
3433
@item 23 : Error while parsing number
3434
This error is returned if GRUB was expecting to read a number and
3435
encountered bad data.
3437
@item 24 : Attempt to access block outside partition
3438
This error is returned if a linear block address is outside of the disk
3439
partition. This generally happens because of a corrupt filesystem on the
3440
disk or a bug in the code handling it in GRUB (it's a great debugging
3443
@item 25 : Disk read error
3444
This error is returned if there is a disk read error when trying to
3445
probe or read data from a particular disk.
3447
@item 26 : Too many symbolic links
3448
This error is returned if the link count is beyond the maximum
3449
(currently 5), possibly the symbolic links are looped.
3451
@item 27 : Unrecognized command
3452
This error is returned if an unrecognized command is entered on the
3453
command-line or in a boot sequence section of a configuration file and
3454
that entry is selected.
3456
@item 28 : Selected item cannot fit into memory
3457
This error is returned if a kernel, module, or raw file load command is
3458
either trying to load its data such that it won't fit into memory or it
3461
@item 29 : Disk write error
3462
This error is returned if there is a disk write error when trying to
3463
write to a particular disk. This would generally only occur during an
3464
install of set active partition command.
3466
@item 30 : Invalid argument
3467
This error is returned if an argument specified to a command is invalid.
3469
@item 31 : File is not sector aligned
3470
This error may occur only when you access a ReiserFS partition by
3471
block-lists (e.g. the command @command{install}). In this case, you
3472
should mount the partition with the @samp{-o notail} option.
3474
@item 32 : Must be authenticated
3475
This error is returned if you try to run a locked entry. You should
3476
enter a correct password before running such an entry.
3478
@item 33 : Serial device not configured
3479
This error is returned if you try to change your terminal to a serial
3480
one before initializing any serial device.
3482
@item 34 : No spare sectors on the disk
3483
This error is returned if a disk doesn't have enough spare space. This
3484
happens when you try to embed Stage 1.5 into the unused sectors after
3485
the MBR, but the first partition starts right after the MBR or they are
3490
@node Invoking the grub shell
3491
@chapter Invoking the grub shell
3493
This chapter documents the grub shell @command{grub}. Note that the grub
3494
shell is an emulator; it doesn't run under the native environment, so it
3495
sometimes does something wrong. Therefore, you shouldn't trust it too
3496
much. If there is anything wrong with it, don't hesitate to try the
3497
native GRUB environment, especially when it guesses a wrong map between
3498
BIOS drives and OS devices.
3501
* Basic usage:: How to use the grub shell
3502
* Installation under UNIX:: How to install GRUB via @command{grub}
3503
* Device map:: The map between BIOS drives and OS devices
3508
@section Introduction into the grub shell
3510
You can use the command @command{grub} for installing GRUB under your
3511
operating systems and for a testbed when you add a new feature into GRUB
3512
or when fixing a bug. @command{grub} is almost the same as the Stage 2,
3513
and, in fact, it shares the source code with the Stage 2 and you can use
3514
the same commands (@pxref{Commands}) in @command{grub}. It is emulated by
3515
replacing BIOS calls with UNIX system calls and libc functions.
3517
The command @command{grub} accepts the following options:
3521
Print a summary of the command-line options and exit.
3524
Print the version number of GRUB and exit.
3527
Print some verbose messages for debugging purpose.
3529
@item --device-map=@var{file}
3530
Use the device map file @var{file}. The format is described in
3534
Do not probe any floppy drive. This option has no effect if the option
3535
@option{--device-map} is specified (@pxref{Device map}).
3537
@item --probe-second-floppy
3538
Probe the second floppy drive. If this option is not specified, the grub
3539
shell does not probe it, as that sometimes takes a long time. If you
3540
specify the device map file (@pxref{Device map}), the grub shell just
3541
ignores this option.
3543
@item --config-file=@var{file}
3544
Read the configuration file @var{file} instead of
3545
@file{/boot/grub/menu.lst}. The format is the same as the normal GRUB
3546
syntax. See @ref{Filesystem}, for more information.
3548
@item --boot-drive=@var{drive}
3549
Set the stage2 @var{boot_drive} to @var{drive}. This argument should be
3550
an integer (decimal, octal or hexadecimal).
3552
@item --install-partition=@var{par}
3553
Set the stage2 @var{install_partition} to @var{par}. This argument
3554
should be an integer (decimal, octal or hexadecimal).
3556
@item --no-config-file
3557
Do not use the configuration file even if it can be read.
3560
Do not use the screen handling interface by the curses even if it is
3564
This option has the same meaning as @samp{--no-config-file --no-curses}.
3567
Disable writing to any disk.
3570
Wait until a debugger will attach. This option is useful when you want
3571
to debug the startup code.
3575
@node Installation under UNIX
3576
@section How to install GRUB via @command{grub}
3578
The installation procedure is the same as under the @dfn{native} Stage
3579
2. @xref{Installation}, for more information. The command
3580
@command{grub}-specific information is described here.
3582
What you should be careful about is @dfn{buffer cache}. @command{grub}
3583
makes use of raw devices instead of filesystems that your operating
3584
systems serve, so there exists a potential problem that some cache
3585
inconsistency may corrupt your filesystems. What we recommend is:
3589
If you can unmount drives to which GRUB may write any amount of data,
3590
unmount them before running @command{grub}.
3593
If a drive cannot be unmounted but can be mounted with the read-only
3594
flag, mount it in read-only mode. That should be secure.
3597
If a drive must be mounted with the read-write flag, make sure that no
3598
activity is being done on it while the command @command{grub} is
3602
Reboot your operating system as soon as possible. This is probably not
3603
required if you follow the rules above, but reboot is the most secure
3607
In addition, enter the command @command{quit} when you finish the
3608
installation. That is @emph{very important} because @command{quit} makes
3609
the buffer cache consistent. Do not push @key{C-c}.
3611
If you want to install GRUB non-interactively, specify @samp{--batch}
3612
option in the command-line. This is a simple example:
3618
# Use /usr/sbin/grub if you are on an older system.
3619
/sbin/grub --batch <<EOT 1>/dev/null 2>/dev/null
3629
@section The map between BIOS drives and OS devices
3631
When you specify the option @option{--device-map} (@pxref{Basic usage}),
3632
the grub shell creates the @dfn{device map file} automatically unless it
3633
already exists. The file name @file{/boot/grub/device.map} is preferred.
3635
If the device map file exists, the grub shell reads it to map BIOS
3636
drives to OS devices. This file consists of lines like this:
3639
@var{device} @var{file}
3642
@var{device} is a drive specified in the GRUB syntax (@pxref{Device
3643
syntax}), and @var{file} is an OS file, which is normally a device
3646
The reason why the grub shell gives you the device map file is that it
3647
cannot guess the map between BIOS drives and OS devices correctly in
3648
some environments. For example, if you exchange the boot sequence
3649
between IDE and SCSI in your BIOS, it gets the order wrong.
3651
Thus, edit the file if the grub shell makes a mistake. You can put any
3652
comments in the file if needed, as the grub shell assumes that a line is
3653
just a comment if the first character is @samp{#}.
3656
@node Invoking grub-install
3657
@chapter Invoking grub-install
3659
The program @command{grub-install} installs GRUB on your drive using the
3660
grub shell (@pxref{Invoking the grub shell}). You must specify the
3661
device name on which you want to install GRUB, like this:
3664
grub-install @var{install_device}
3667
The device name @var{install_device} is an OS device name or a GRUB
3670
@command{grub-install} accepts the following options:
3674
Print a summary of the command-line options and exit.
3677
Print the version number of GRUB and exit.
3680
Force GRUB to use LBA mode even for a buggy BIOS. Use this option only
3681
if your BIOS doesn't work properly in LBA mode even though it supports
3684
@item --root-directory=@var{dir}
3685
Install GRUB images under the directory @var{dir} instead of the root
3686
directory. This option is useful when you want to install GRUB into a
3687
separate partition or a removable disk. Here is an example in which
3688
you have a separate @dfn{boot} partition which is mounted on
3692
@kbd{grub-install --root-directory=/boot hd0}
3695
@item --grub-shell=@var{file}
3696
Use @var{file} as the grub shell. You can append arbitrary options to
3697
@var{file} after the file name, like this:
3700
@kbd{grub-install --grub-shell="grub --read-only" /dev/fd0}
3704
Recheck the device map, even if @file{/boot/grub/device.map} already
3705
exists. You should use this option whenever you add/remove a disk
3706
into/from your computer.
3710
@node Invoking grub-md5-crypt
3711
@chapter Invoking grub-md5-crypt
3713
The program @command{grub-md5-crypt} encrypts a password in MD5 format.
3714
This is just a frontend of the grub shell (@pxref{Invoking the grub
3715
shell}). Passwords encrypted by this program can be used with the
3716
command @command{password} (@pxref{password}).
3718
@command{grub-md5-crypt} accepts the following options:
3722
Print a summary of the command-line options and exit.
3725
Print the version information and exit.
3727
@item --grub-shell=@var{file}
3728
Use @var{file} as the grub shell.
3732
@node Invoking grub-terminfo
3733
@chapter Invoking grub-terminfo
3735
The program @command{grub-terminfo} generates a terminfo command from
3736
a terminfo name (@pxref{terminfo}). The result can be used in the
3737
configuration file, to define escape sequences. Because GRUB assumes
3738
that your terminal is vt100-compatible by default, this would be
3739
useful only if your terminal is uncommon (such as vt52).
3741
@command{grub-terminfo} accepts the following options:
3745
Print a summary of the command-line options and exit.
3748
Print the version information and exit.
3751
You must specify one argument to this command. For example:
3754
@kbd{grub-terminfo vt52}
3758
@node Invoking grub-set-default
3759
@chapter Invoking grub-set-default
3761
The program @command{grub-set-default} sets the default boot entry for
3762
GRUB. This automatically creates a file named @file{default} under
3763
your GRUB directory (i.e. @file{/boot/grub}), if it is not
3764
present. This file is used to determine the default boot entry when
3765
GRUB boots up your system when you use @samp{default saved} in your
3766
configuration file (@pxref{default}), and to save next default boot
3767
entry when you use @samp{savedefault} in a boot entry
3768
(@pxref{savedefault}).
3770
@command{grub-set-default} accepts the following options:
3774
Print a summary of the command-line options and exit.
3777
Print the version information and exit.
3779
@item --root-directory=@var{dir}
3780
Use the directory @var{dir} instead of the root directory
3781
(i.e. @file{/}) to define the location of the default file. This
3782
is useful when you mount a disk which is used for another system.
3785
You must specify a single argument to @command{grub-set-default}. This
3786
argument is normally the number of a default boot entry. For example,
3787
if you have this configuration file:
3804
and if you want to set the next default boot entry to GNU/Linux, you
3805
may execute this command:
3808
@kbd{grub-set-default 1}
3811
Because the entry for GNU/Linux is @samp{1}. Note that entries are
3812
counted from zero. So, if you want to specify GNU/Hurd here, then you
3813
should specify @samp{0}.
3815
This feature is very useful if you want to test a new kernel or to
3816
make your system quite robust. @xref{Making your system robust}, for
3817
more hints about how to set up a robust system.
3820
@node Invoking mbchk
3821
@chapter Invoking mbchk
3823
The program @command{mbchk} checks for the format of a Multiboot
3824
kernel. We recommend using this program before booting your own kernel
3827
@command{mbchk} accepts the following options:
3831
Print a summary of the command-line options and exit.
3834
Print the version number of GRUB and exit.
3837
Suppress all normal output.
3841
@node Obtaining and Building GRUB
3842
@appendix How to obtain and build GRUB
3845
@strong{Caution:} GRUB requires binutils-2.9.1.0.23 or later because the
3846
GNU assembler has been changed so that it can produce real 16bits
3847
machine code between 2.9.1 and 2.9.1.0.x. See
3848
@uref{http://sources.redhat.com/binutils/}, to obtain information on
3849
how to get the latest version.
3852
GRUB is available from the GNU alpha archive site
3853
@uref{ftp://alpha.gnu.org/gnu/grub} or any of its mirrors. The file
3854
will be named grub-version.tar.gz. The current version is
3855
@value{VERSION}, so the file you should grab is:
3857
@uref{ftp://alpha.gnu.org/gnu/grub/grub-@value{VERSION}.tar.gz}
3859
To unbundle GRUB use the instruction:
3862
@kbd{zcat grub-@value{VERSION}.tar.gz | tar xvf -}
3865
which will create a directory called @file{grub-@value{VERSION}} with
3866
all the sources. You can look at the file @file{INSTALL} for detailed
3867
instructions on how to build and install GRUB, but you should be able to
3872
@kbd{cd grub-@value{VERSION}}
3878
This will install the grub shell @file{grub} (@pxref{Invoking the grub
3879
shell}), the Multiboot checker @file{mbchk} (@pxref{Invoking mbchk}),
3880
and the GRUB images. This will also install the GRUB manual.
3882
Also, the latest version is available from the CVS. See
3883
@uref{http://savannah.gnu.org/cvs/?group=grub} for more information.
3886
@node Reporting bugs
3887
@appendix Reporting bugs
3889
These are the guideline for how to report bugs. Take a look at this
3890
list below before you submit bugs:
3894
Before getting unsettled, read this manual through and through. Also,
3895
see the @uref{http://www.gnu.org/software/grub/grub-faq.html, GNU GRUB FAQ}.
3898
Always mention the information on your GRUB. The version number and the
3899
configuration are quite important. If you build it yourself, write the
3900
options specified to the configure script and your operating system,
3901
including the versions of gcc and binutils.
3904
If you have trouble with the installation, inform us of how you
3905
installed GRUB. Don't omit error messages, if any. Just @samp{GRUB hangs
3906
up when it boots} is not enough.
3908
The information on your hardware is also essential. These are especially
3909
important: the geometries and the partition tables of your hard disk
3910
drives and your BIOS.
3913
If GRUB cannot boot your operating system, write down
3914
@emph{everything} you see on the screen. Don't paraphrase them, like
3915
@samp{The foo OS crashes with GRUB, even though it can boot with the
3916
bar boot loader just fine}. Mention the commands you executed, the
3917
messages printed by them, and information on your operating system
3918
including the version number.
3921
Explain what you wanted to do. It is very useful to know your purpose
3922
and your wish, and how GRUB didn't satisfy you.
3925
If you can investigate the problem yourself, please do. That will give
3926
you and us much more information on the problem. Attaching a patch is
3929
When you attach a patch, make the patch in unified diff format, and
3930
write ChangeLog entries. But, even when you make a patch, don't forget
3931
to explain the problem, so that we can understand what your patch is
3935
Write down anything that you think might be related. Please understand
3936
that we often need to reproduce the same problem you encounterred in our
3937
environment. So your information should be sufficient for us to do the
3938
same thing---Don't forget that we cannot see your computer directly. If
3939
you are not sure whether to state a fact or leave it out, state it!
3940
Reporting too many things is much better than omitting something
3944
If you follow the guideline above, submit a report to the
3945
@uref{http://savannah.gnu.org/bugs/?group=grub, Bug Tracking System}.
3946
Alternatively, you can submit a report via electronic mail to
3947
@email{bug-grub@@gnu.org}, but we strongly recommend that you use the
3948
Bug Tracking System, because e-mail can be passed over easily.
3950
Once we get your report, we will try to fix the bugs.
3954
@appendix Where GRUB will go
3956
We started the next generation of GRUB, GRUB 2. This will include
3957
internationalization, dynamic module loading, real memory management,
3958
multiple architecture support, a scripting language, and many other
3959
nice feature. If you are interested in the development of GRUB 2, take
3960
a look at @uref{http://www.gnu.org/software/grub/grub.html, the
3964
@c Separate the programming guide.
3965
@include internals.texi
3971
@c Currently, we use only the Concept Index.
3979
This is the second attempt to rewrite the manual. The status is
3980
mostly complete, but I need to check the spelling by ispell, and add
3981
more indices. Perhaps I also have to let some English native speakers
3982
proofread this manual through. My English is syntactically almost
3983
perfect, but sometimes (often?) awful in the nuance. Hehe, I can't be an
3984
English poet for now.