Using pygrub to boot a domU kernel

Using pygrub, each domU can boot with its own kernel instead of using the dom0 kernel, which lifes easier for updates and multi distribution xen installs. You need to have first a working domU.

On the domU

Install the xen kernel and grub

aptitude install linux-image-2.6-xen-amd64 grub

Create the environment needed for running update-grub

mkdir /boot/grub
echo "(hd0) /dev/sda" > /boot/grub/device.map
mknod /dev/sda b 202 0

Create first /boot/grub/menu.lst based on the content of /boot

update-grub

Check the default grub root matches the partition where /boot/grub lives. If /boot/grub is on /dev/sda2, you need to have # groot=(hd0,1) in your /boot/grub/menu.lst.

After editing this file, you need to re-run update-grub to propagate the changes.

sed -i -e 's/^# groot=(hd0)/# groot=(hd0,1)/' \
/boot/grub/menu.lst

update-grub

On the dom0

Replace the kernel and ramdisk parameters in the domU config file with

bootloader      = '/usr/lib/xen-3.2-1/bin/pygrub'

If you get Error: Boot loader didn't return any data! you need to have the system partition as the first partition comming in your domU.cfg something akin to

disk        = [
                  'phy:/dev/vg02/sandbox.openforce.com-disk,sda2,w',
                  'phy:/dev/vg02/sandbox.openforce.com-swap,sda1,w',
              ]