Use tar better
You should also do it with a Linux not using / because you can be copying all the mounted partitions!
Say using a Live CD. Your source / is in sda3 and the target is in sde9, assuming you have formatted sde9 to the filing system of your choice. These are commands run at root console
Code:
mkdir /mnt/sda3
mkdir /mnt/sde9
mount /dev/sda3 /mnt/sda3
mount /dev/sde9 /mnt/sde9
cd /mnt/sda3
tar cf - . | (cd /mnt/sde9; tar xf -)
The complete partition of / will be found in sde9.
If you use dd you have to make sure the size matches up. With tar you don't have to bother about the size.
