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(grub.info)Installing GRUB using grub-install

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

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

   Unfortunately, if you do want to install GRUB under a UNIX-like OS
(such as GNU), invoke the program `grub-install' (Note: Invoking
grub-install) as the superuser ("root").

   The usage is basically very easy. You only need to specify one
argument to the program, namely, where to install GRUB. The argument
can be either of a device file or a GRUB's drive/partition. So, this
will install GRUB into the MBR of the first IDE disk under Linux:

     # grub-install /dev/hda

   Likewise, under Hurd, this has the same effect:

     # grub-install /dev/hd0

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

     # grub-install '(hd0)'

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

     # mke2fs /dev/fd0
     # mount -t ext2 /dev/fd0 /mnt
     # grub-install --root-directory=/mnt '(fd0)'
     # umount /mnt

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

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

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

   Note that `grub-install' is actually just a shell script and the
real task is done by the grub shell `grub' (Note: Invoking the grub
shell). Therefore, you may run `grub' directly to install GRUB,
without using `grub-install'. Don't do that, however, unless you are
very familiar with the internals of GRUB. Installing a boot loader on a
running OS may be extremely dangerous.