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GRUB (v.1)

Configuration

The GRUB configuration file is /boot/grub/menu.lst by default in Debian. You may see references to /etc/grub.conf used in other configurations.

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

Please note that the root command is not related to the root parameter for the linux kernel. root specifies the partition to look relative paths . If you have a /boot partition in (hd0,0) then

 root (hd0,0)
 kernel ''vmlinuz root=LABEL=''

Is the same as

 kernel (hd0,0)/vmlinuz

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:

linux

grub

First IDE bus, master

hda

hd0

First IDE bus, master, first primary partition

hda1

hd0,0

First IDE bus, slave, first extended partition

hdb5

hd1,4

Installation

To install grub as the master boot system for the system, just exec:

 # grub-install /dev/hda

No more, no less. From now you only need to edit /boot/grub/menu.lst.

Examples

Linux

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, and / is in hda3

 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

I see /boot is in (hd0,1). Then my lines are:

 title Linux
 root (hd0,1)
 kernel /vmlinuz root=/dev/hda3 vga=792
 initrd /initrd.img

Windows on hda1

These are the lines I have to boot windoze, located at hda1

 title ["SuckingXP"]
 rootnoverify (hd0,0)
 makeactive
 chainloader  +1

Windows in other place not in hda1

If the disk order has changed the ms boot system gets confused and refuses to boot. If you have it in hdb1 this can solve the problem:

 title Windoze
  map (hd0) (hd1)
  map (hd1) (hd0)
  rootnoverify (hd1,0)
  makeactive
  chainloader +1

You can do more magic hiding partitions with the command hide. For example, if it's in hda2:

 title Windoze
  hide (hd0,0)
  rootnoverify (hd0,1)
  makeactive
  chainloader +1

> note: ms boot system has several critical holes, and its behaviour changes depending in version and patch level

See Also


CategoryBootProcess