Commit 1c41aa78 authored by Colin Watson's avatar Colin Watson

* docs/grub.texi (Chain-loading): New section.

(DOS/Windows): New section, borrowed from GRUB Legacy with details
adjusted for GRUB 2.
(SCO UnixWare): Likewise.
(QNX): Likewise.
(chainloader): Add reference to `Block list syntax'.
(drivemap): New section.
(parttool): New section.
parent bb8ea0f5
2010-06-02 Colin Watson <cjwatson@ubuntu.com>
* docs/grub.texi (Chain-loading): New section.
(DOS/Windows): New section, borrowed from GRUB Legacy with details
adjusted for GRUB 2.
(SCO UnixWare): Likewise.
(QNX): Likewise.
(chainloader): Add reference to `Block list syntax'.
(drivemap): New section.
(parttool): New section.
2010-06-02 Colin Watson <cjwatson@ubuntu.com>
* docs/grub.texi (GNU GRUB manual): Remove reference to `Invoking
......
......@@ -647,6 +647,35 @@ use more complicated instructions. @xref{DOS/Windows}, for more
information.
@node Chain-loading
@subsection Chain-loading an OS
Operating systems that do not support Multiboot and do not have specific
support in GRUB (specific support is available for Linux, FreeBSD, NetBSD
and OpenBSD) must be chain-loaded, which involves loading another boot
loader and jumping to it in real mode.
The @command{chainloader} command (@pxref{chainloader}) is used to set this
up. It is normally also necessary to load some GRUB modules and set the
appropriate root device. Putting this together, we get something like this,
for a Windows system on the first partition of the first hard disk:
@verbatim
menuentry "Windows" {
insmod chain
insmod ntfs
set root=(hd0,1)
chainloader +1
}
@end verbatim
@c FIXME: document UUIDs.
On systems with multiple hard disks, an additional workaround may be
required. @xref{DOS/Windows}.
Chain-loading is only supported on PC BIOS and EFI platforms.
@node OS-specific notes
@section Some caveats on OS-specific issues
......@@ -655,6 +684,9 @@ Here, we describe some caveats on several operating systems.
@menu
* GNU/Hurd::
* GNU/Linux::
* DOS/Windows::
* SCO UnixWare::
* QNX::
@end menu
......@@ -696,6 +728,87 @@ the size, run the command @command{uppermem} @emph{before} loading the
kernel. @xref{uppermem}, for more information.
@node DOS/Windows
@subsection DOS/Windows
GRUB cannot boot DOS or Windows directly, so you must chain-load them
(@pxref{Chain-loading}). However, their boot loaders have some critical
deficiencies, so it may not work to just chain-load them. To overcome
the problems, GRUB provides you with two helper functions.
If you have installed DOS (or Windows) on a non-first hard disk, you
have to use the disk swapping technique, because that OS cannot boot
from any disks but the first one. The workaround used in GRUB is the
command @command{drivemap} (@pxref{drivemap}), like this:
@example
drivemap -s (hd0) (hd1)
@end example
This performs a @dfn{virtual} swap between your first and second hard
drive.
@strong{Caution:} This is effective only if DOS (or Windows) uses BIOS
to access the swapped disks. If that OS uses a special driver for the
disks, this probably won't work.
Another problem arises if you installed more than one set of DOS/Windows
onto one disk, because they could be confused if there are more than one
primary partitions for DOS/Windows. Certainly you should avoid doing
this, but there is a solution if you do want to do so. Use the partition
hiding/unhiding technique.
If GRUB @dfn{hides} a DOS (or Windows) partition (@pxref{parttool}), DOS (or
Windows) will ignore the partition. If GRUB @dfn{unhides} a DOS (or Windows)
partition, DOS (or Windows) will detect the partition. Thus, if you have
installed DOS (or Windows) on the first and the second partition of the
first hard disk, and you want to boot the copy on the first partition, do
the following:
@example
@group
parttool (hd0,1) hidden-
parttool (hd0,2) hidden+
set root=(hd0,1)
chainloader +1
parttool @verb{'${root}'} boot+
boot
@end group
@end example
@node SCO UnixWare
@subsection SCO UnixWare
It is known that the signature in the boot loader for SCO UnixWare is
wrong, so you will have to specify the option @option{--force} to
@command{chainloader} (@pxref{chainloader}), like this:
@example
@group
set root=(hd1,1)
chainloader --force +1
parttool @verb{'${root}'} boot+
boot
@end group
@end example
@node QNX
@subsection QNX
QNX seems to use a bigger boot loader, so you need to boot it up, like
this:
@example
@group
set root=(hd1,2)
chainloader +4
boot
@end group
@end example
@node Configuration
@chapter Writing your own configuration file
......@@ -1325,6 +1438,7 @@ you forget a command, you can run the command @command{help}
* configfile:: Load a configuration file
* crc:: Calculate CRC32 checksums
* date:: Display or set current date and time
* drivemap:: Map a drive to another
* echo:: Display a line of text
* export:: Export an environment variable
* gettext:: Translate a string
......@@ -1334,6 +1448,7 @@ you forget a command, you can run the command @command{help}
* insmod:: Insert a module
* keystatus:: Check key modifier status
* ls:: List devices or files
* parttool:: Modify partition table entries
* play:: Play a tune
* reboot:: Reboot your computer
* set:: Set an environment variable
......@@ -1399,11 +1514,12 @@ grub> @kbd{cat /etc/fstab}
@deffn Command chainloader [@option{--force}] file
Load @var{file} as a chain-loader. Like any other file loaded by the
filesystem code, it can use the blocklist notation to grab the first
sector of the current partition with @samp{+1}. If you specify the
option @option{--force}, then load @var{file} forcibly, whether it has a
correct signature or not. This is required when you want to load a
defective boot loader, such as SCO UnixWare 7.1 (@pxref{SCO UnixWare}).
filesystem code, it can use the blocklist notation (@pxref{Block list
syntax}) to grab the first sector of the current partition with @samp{+1}.
If you specify the option @option{--force}, then load @var{file} forcibly,
whether it has a correct signature or not. This is required when you want to
load a defective boot loader, such as SCO UnixWare 7.1 (@pxref{SCO
UnixWare}).
@end deffn
......@@ -1458,6 +1574,32 @@ hour, minute, and second unchanged.
@end deffn
@node drivemap
@subsection drivemap
@deffn Command drivemap @option{-l}|@option{-r}|[@option{-s}] @
from_drive to_drive
Without options, map the drive @var{from_drive} to the drive @var{to_drive}.
This is necessary when you chain-load some operating systems, such as DOS,
if such an OS resides at a non-first drive. For convenience, any partition
suffix on the drive is ignored, so you can safely use @verb{'${root}'} as a
drive specification.
With the @option{-s} option, perform the reverse mapping as well, swapping
the two drives.
With the @option{-l} option, list the current mappings.
With the @option{-r} option, reset all mappings to the default values.
For example:
@example
drivemap -s (hd0) (hd1)
@end example
@end deffn
@node echo
@subsection echo
......@@ -1605,6 +1747,41 @@ name syntax}), then list the contents of that directory.
@end deffn
@node parttool
@subsection parttool
@deffn Command parttool partition commands
Make various modifications to partition table entries.
Each @var{command} is either a boolean option, in which case it must be
followed with @samp{+} or @samp{-} (with no intervening space) to enable or
disable that option, or else it takes a value in the form
@samp{@var{command}=@var{value}}.
Currently, @command{parttool} is only useful on DOS partition tables (also
known as Master Boot Record, or MBR). On these partition tables, the
following commands are available:
@table @asis
@item @samp{boot} (boolean)
When enabled, this makes the selected partition be the active (bootable)
partition on its disk, clearing the active flag on all other partitions.
This command is limited to @emph{primary} partitions.
@item @samp{type} (value)
Change the type of an existing partition. The value must be a number in the
range 0-0xFF (prefix with @samp{0x} to enter it in hexadecimal).
@item @samp{hidden} (boolean)
When enabled, this hides the selected partition by setting the @dfn{hidden}
bit in its partition type code; when disabled, unhides the selected
partition by clearing this bit. This is useful only when booting DOS or
Wwindows and multiple primary FAT partitions exist in one disk. See also
@ref{DOS/Windows}.
@end table
@end deffn
@node play
@subsection play
......
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