Trying to move root partition

[Paul Galbraith]

I want to move my root partition to a new drive.  I created a new partition and formatted it, and then used cp -a from a knoppix CD to copy the root parition files over to the new parition, and changed fstab to point to the new location.  However, when I reboot from the new location, I get this error and a kernel panic, and the system freezes during boot:       mout: /dev2/root2 is not a valid block device   Does anyone know what happened?