GNU/Linux Desktop Survival Guide by Graham Williams
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GRUB: The Grand Unified Boot Loader

Debian Packages: grub

Grub (the GRand Unified Bootloader) is a boot loader designed to address the limitations of lilo. It makes up for numerous deficiencies in many PC BIOSs while providing full-featured command line and graphical interfaces. Grub recognises fdisk partitions, can dynamically read Linux ext2fs, and MSDOS FAT16 and FAT32 filesystems, and can boot multiboot-compliant kernels (such as GNU Mach), as well as standard Linux and MS/Windows kernels.

A good introduction to grub is available from http://www.gnu.org/software/grub/grub.html and a good guide to multi-boot setup is http://www.tldp.org/HOWTO/Multiboot-with-GRUB.html. This latter resource looks at multi-booting four operating systems although the information is still useful if all you want is to multiboot just two.

To switch from lilo to grub simply install it with:

  # wajig install grub
  # grub-install /dev/hda
  # update-grub

This creates a /boot/grub/menu.lst file which you might like to review just to make sure it looks okay. For most simple situations it should be fine.

For a dual boot with MS/Windows/NT on the first partition and Linux on the second (like Mint), you may need to change the default locations of Linux. Look at /boot/grub/menu.lst to see if the following two lines have been changed:

# kopt=root=/dev/hda1 ro
# groot=(hd0,0)

to

# kopt=root=/dev/hda2 ro
# groot=(hd0,1)

Also, add to the end of the file:

title           Windows NT
rootnoverify    (hd0,0)
makeactive
chainloader     +1

Once it looks okay, run update-grub then reboot!

When installing new kernels you can have the new kernel automatically added to the menu by adding the following lines to /etc/kernel-img.conf (and in fact making the file look the same as) :

  # Turn off Lilo stuff
  do_symlinks = no
  do_bootloader = no

  # Initrds are OK for GRUB
  do_initrd = yes

  # Run cool GRUB stuff
  postinst_hook = /sbin/update-grub
  postrm_hook = /sbin/update-grub

If you start having problems booting, at the grub menu type c to get the command line. Try:

  root (hd0,4)     (/dev/hda5)
  kernel /boot/vmlinuz-2.4.18-bf2.4 root=/dev/hda5 ro
  boot

More information on using grub is available from the Linux Journal.