A little while ago I wrote about my problems booting Linux on a Dell Optiplex 320 the solution was to install Grub 2 and tweak the boot options. Since then I have run into a couple other problems which have required me to learn a little more about managing Grub 2 on a Debian based system (Ubuntu in my case). Specifically, I want my changes to grub.cfg to persist between kernel upgrades. So here is what I have learned.

Background

Every time a new kernel is installed, /usr/sbin/update-grub is called. This re-writes /boot/grub/grub.cfg. So any changes you make to grub.cfg directly are obliterated. However, the new grub.cfg is generated from:

• /boot/grub/grub.cfg
• /etc/grub.d

So if I know how to edit those files, I can make my changes persistent.

Changing default kernel options

/etc/default/grub allows you to set parameters that appear in the grub.cfg file. In my case I wanted every “linux” command to have the “acpi=off” option appended. So I added the following line to /etc/default/grub:
GRUB_CMDLINE_LINUX=acpi=off

Now just run
sudo /usr/sbin/update-grub
and presto! All the “linux” commands have acpi=off appended.

Adding a boot option

My other problem was that everytime grub.cfg was updated, my Windows boot option was deleted. To fix that I needed to add a new file to /etc/grub.d. Read /etc/grub.d/README for more details, but the summary is:

1. Create a file named “21_windows”
2. Put the following code in the file:
   #!/bin/bash
set -e
cat << EOF
menuentry "Other Operating Systems" {
set root=(hd0,1)
title Other Operating Systems
}menuentry "Microsoft Windows XP Professional" {
set root=(hd0,1)
chainloader +1
boot
}
EOF
3. Make the file executable:
   sudo chmod 755 /etc/grub.d/21_windows
4. Re-run
   sudo /usr/sbin/update-grub

That is all, hope it helps.