I was doing that but decided it was easier to just do the updates and fix anything that breaks because I could not replicate the hardware RAID card I have in the server itself inside the VM. So far I have not run into many problems but the number one problem so far is the building of the raid card's module via DKMS, which somehow doesn't do it right with the newer 3.2.x kernels.Another approach is to run a parallel server, perhaps in a VirtualBox VM on your desktop. Configure the VM to be the same as your actual server. The simplest method to do this is to install 12.04 into the VM, then use rsync to make the VM copy a clone of the actual one. Then run the updates on the VM server and see if they cause any problems. If not, then you can run them on the real server as well.