I've found it difficult to move /var while the system is running with /var mounted.
What I have done is,
copy /var... to the new partition.
reboot using a live distro, like arch-linux, gparted or slax (I use gparted live cd (allows "make active boot" per HDD)).
edit the "/etc/fstab", changing the address of the relevant line (my system has multiple partitions, /var is one of them).
then you may remove the data from the old /var "partition".
If it is just a directory, you'd be best off, doing a re-install with partitioning in mind.
Last edited by GlennsPref; 02-22-2012 at 04:43 AM.