[server] "ALERT! /dev/disk/by-uuid/X-X-X-X does not exist." when booting Ubuntu with Xen

Well, I decided to go ahead and try Ubuntu server with Xen to virtualize stuff. This is mostly because my server is a bit older Opteron machine, which doesn't support full hardware virtualization, so KVM is out and VirtualBox doesn't have as good performance as Xen. Also, I'd like to use zfs (as it's finally supported properly in Linux, yay!) from Dom0 as the storage for various virtual machines.

So, I tried to install Xen according to instructions (minus LVM part): https://help.ubuntu.com/community/Xen

But I get this error when trying to boot Ubuntu with Xen. When I choose plain Ubuntu from the Grub menu, then it boots just fine.


Gave up waiting for root device. Common probleMs:
— Boot args (cat /proc/cmdline)
— Check rootdelay= (did the systeM wait long enough?)
— Check root= (did the systeri wait for the right device?)
— Missing Modules (cat /proc/Modules; ls /dev)
ALERT? /dev/disk/by-uuid/X—X—X—X—X does not exist.
Dropping to a shell!


Any idea how to solve this?