After upgrading my virtualized Ubuntu 11.10 installation to Ubuntu 12.04 Precise Pangolin, I’ve had strange problems on booting up the virtual machine: Sometimes it booted up smoothly, sometimes it hung, sometimes it reported a read-only filesystem due to errors (which actually could not be found using fsck). After some investigation, I decided to re-install the system.

I wanted to install Ubuntu 12.04 LTS para-virtualized (PV), but this is not supported out of the box by Citrix XenServer 5.6 SP2. However, I’ve found some really useful instructions in the Citrix Forums written for for Ubuntu 11.04, also working for Ubuntu 12.04:

1. Enter the XenServer Console and get the UUID of the Ubuntu 10.10 template:

   xe template-list name-label="Ubuntu Lucid Lynx 10.04 (64-bit) (experimental)" --minimal

2. Clone the Ubuntu 10.10 template:

   xe vm-clone uuid=[UUID from step 1 here] new-name-label="Ubuntu Precise Pangolin 12.04 (64-bit)"

3. Configute the new Ubuntu 12.04 template:

   xe template-param-set other-config:default_template=true other-config:debian-release=precise uuid=[UUID from step 2 here]

4. Create a new VM and choose your newly created Ubuntu 12.04 template.
5. Enter the following url under “Install from URL:”

   http://archive.ubuntu.net/ubuntu/

6. Create a separate /boot partition at the beginning of the virtual disk (I chose 256 MB).
7. After the installation is completed, log into your new VM and become root.

   sudo -s

8. Install the virtual kernel image:

   apt-get install linux-virtual linux-image-virtual linux-headers-virtual

9. Remove the generic kernel image:

   apt-get remove linux-generic linux-headers-generic linux-image-generic

10. Update the grub boot loader:

    update-grub

11. Insert the XenServer Tools xs-tools.iso and mount it:

    mount /dev/xvdd /mnt

12. Install the XenServer Tools:

    cd /mnt/Linux
    dpkg -i *amd64.deb

13. Unmount the ISO and reboot:

    cd
    umount /mnt
    reboot

14. That’s it!
    

I haven’t tried, but this might work for Citrix XenServer 6, too.