I'm migrating some machines with problematic hardware to OpenVZ containers (as well as to save on energy).
rsync -arvpz --numeric-ids --exclude=/dev --exclude=/proc --exclude=/tmp --exclude=/boot -e ssh firstname.lastname@example.org:/ /var/lib/vz/private/838
Seems to me that it is much easier to go from a real machine to an OpenVZ container than vice-versa.
The above script is an example I found at the OpenVZ site. In reality I had to tailor mine so that I wasn't transferring data I didn't need.