In /sbin/functions.sh there is a is_xenU_sys() function, that tests if the system is a xenU domain. If so, things like /etc/init.d/clock and so don't try to access hardware that they can't reach - this is a really nice feature I think.
Unfortunately, the test to check for a xenU domain is faulty; the implementation is currently as follows:
[[ -d /proc/xen && ! -f /proc/xen/privcmd ]]
The first check tests if the system is a Xen guest domain or not. The second check is there to see the difference between a xen0 and a xenU domain. Unfortunately, (at least in xen 3.0.1) the /proc/xen/privcmd file exists both in xen0 and in xenU domains.
So the check now thinks that xenU domains are xen0 domains.
I'm not quite sure what the best way is to discriminate between xen0 and xenU domains.
*** This bug has been marked as a duplicate of 107976 ***