vzmigrate --online dest-host VEIDNO
eg.:
vzmigrate --oneline 192.168.1.55 101
One option I would recommend is "--keep-dst", that way if the migration is interrupted you can still bring the VPS back up on the original host. After the migration is successful you can manually destroy it.
OpenVZ has a good writeup on this including Checkpointing and Restoring etc:........
Starting online migration of CT 300 to 192.168.5.45
Error: vzcpt module is not loaded on the source node
Error: Can't continue online migration
Error: vzcpt module is not loaded on the source node
Error: Can't continue online migration
This is a very easy fix, you just load the appropriate modules on the source and target node (althoughI don't know why the vzmigrate tool can't do that for the user on both ends):........