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GRUB

Configuration

The GRUB configuration file is /boot/grub/menu.lst. In some places you will see references to /etc/grub.conf, but that file does not exists in debian (note: at least not in my machine)

It must contain at least these lines:

 default=0
 timeout=30
 # To boot the default kernel
 title Debian Linux
 root (hd0,1)
 kernel /boot/vmlinuz root=LABEL=/
 initrd /boot/initrd.img

Quick command overview

• default: the default OS to boot if you do not hit any key (surprised?). Note the first is the 0.

• timeout: the time in seconds to wait before the default OS is booted.

• tittle: the text that is going to appear in the menu. Starts a OS section until other tittle line is found.

• root: the partition where /boot directory is. All paths will be relative to this partition, so we do not need to especify it for each file

• kernel: the linux kernel image to load along with all the options for it

• initrd: the initrd image to boot the kernel with.

Please note that the paths are relative to the partion. If you have a /boot partition the you should write:

 kernel ''vmlinuz root=LABEL=''
 initrd /initrd.img

GRUB device and partition naming

Grub uses numbers to name hard disk and partitions begining with 0. This is a bit confusing for the linux user used to call hda1 the first disk - first partition. A simple table illustrates it:

If you do not know where /boot lives just exec grub and try to find a file, example:

 grub> kernel (hd0,1)/bo

And press tab, if boot is found in that partition the line will be completed. This works also on the boot menu. For example, I have windoze in hda1 a /boot partition on hda2:

 grub> kernel (hd0,0)/vm (<- I press TAB here)
 Error 15: File not found

 grub> kernel (hd0,1)/vm (<- I press TAB again, then completes to vmlinuz)
  Possible files are: vmlinuz-2.6.10-1-k7 vmlinuz.old vmlinuz-2.6.11.old vmlinuz vmlinuz-2.6.11

So I see /boot is in hd0,1