When I installed ubuntu 13.04 desktop on a Citrix Xenserver 6.2 hypervisor I could not use XenMotion to live migrate the vm from one hypervisor to another since the xentools could not be installed via gui. The problem solved by running the following commands on a terminal session on ubuntu desktop (this works with the server edition as well).
First mount the dvddrive to xentools.iso on xencenter gui or by executing:
sudo mount /dev/cdrom /mnt
on a terminal console. Then run:
cd <mounted path>/Linux (in our case
ls -la (to see the included packages) and finally
sudo dpkg -i ./<the package>.deb (there are 2 different versions for i386 and amd64 architectures)
and reboot the vm.
in my example I run
sudo dpkg -i ./xe-guest-utilities_6.2.0-1120_i386.deb on my i5 box.
Now you are ready to suspend the vm or enable xenmotion and migrate the ubuntu virtual machine to another host.