http://forums.perforce.com/index.php?/topic/2756-ova-and-citrix-xenserver/

Commons OVA issues are caused but the kernel used in the OVA wich is 10.04 server LTS because the kernel used in 10.04 does not suport xen tools unless it's install from a fresh template the reason is because OVA is imported it's run in HVM mode only
make sure to do a backup before you try any of these for my self i all way work with a full clone to do my test

all instruction in bold are to be type in console
to remove VMware tools and the installation of xen tools look at the first post

TAKE NOTE : in case the console stop working in XENCENTER for the VM , just restart the xencenter

here the few solution i got to make it work

First solution : Use it as is  

import the OVA , and only remove the vmware tools , the VM will work . Keep in mind the xencenter will have minimal control of the VM , only forced reboot and shutdown , no memory management  ( tested and working for me )

Second solution : update the VM from 10.04 to 12.04

import the OVA , and remove the vmware tools ,  update the server to 12.04 LTS

instruction to update It :

• as root do : apt-get update
• then apt-get upgrade
• once that is done you need to upgrade the server to 12.04 :
• apt-get install update-manager-core
• do-release-upgrade ( follow the instruction they will ask a few question )
• next time we will reboot we will loose the console so to make sure it's does not append
• cp /etc/init/tty1.conf /etc/init/hvco.conf
• edit the hvc0.conf and replace all the tty1 by hvc0
• reboot
• install the xen tools then reboot

the VM will work and xencenter will have complete control of the VM and memory management ( tested and working for me )

Third Solution :dont use Commons OVA , and install it in one of the other working OVA ( probablement GIT Fusion ) not tested

Fourth solution : change the VM from HVM to PV

import the OVA , and remove the vmware tools
instruction to update It :

in the Commons console of the VM

• as root do : apt-get update
• then apt-get upgrade
• next time we will reboot we will loose the console so to make sure it's does not append
• cp /etc/init/tty1.conf  /etc/init/hvco.conf
• edit the hvc0.conf  and replace all the tty1 by hvc0
• install the xen tools then reboot

in the server console

• xe vm-list
• copy the uuid of the VM that's running commons and run the command:
• xe vm-param-set uuid=<vm uuid> HVM-boot-policy=""
• that will set the VM to run as PV  because in place of using the qemu it will use bootloader
• next we need to tell to use grub as boot loader
• xe vm-param-set uuid=<vm uuid> PV-bootloader=pygrub
• restart commons VM

now you will have xencenter with complete control of the VM and memory management