Are you looking to clone the complete hd, or just the partitions? I guess I'm asking if you want the cloned hd to be bootable. You can clone a complete hard drive using the dd command. You need a live-cd that has gparted or a live-cd and parted magic on another cd.
To clone a HD.
Boot to the live cd make sure none of your hd's are mounted, then look to see how your hd's are list in linux. Open a terminal window and type the command.
Write down how linux lists the hd's,
Lets say your primary master with your OS is listed as /dev/sda1
and your spare drive is listed as /dev/sdb1
to clone sda to sdb the command would be
dd if=/dev/sda of=/dev/sdb bs=32256
After it is done you can either boot to your primary OS and if it has gparted or some other partition editor you can resize the new cloned hd to expand the partition if you have free space you want to use. Or boot to the Parted Magic cd and expand the partition.
I just cloned my Debian system last night that was on a 80Gb sata drive to a 320Gb sata drive.
Note: If you are going to expand the / partition of the cloned drive, make sure it is not mounted. You will need to delete the swap partition then expand the / partition, leave enough free space to create the swap partition again. It will take awhile to expand the partition, after it is done shut down connect the new cloned hd in the place your old hd is. Boot up and all should be well.