Shortly said, yeah, as far as it has dd (or equivalent) in it.
If sda was your primary harddisk which you wanted to clone onto sdb, your secondary harddisk, which was identical drive (or at least equally sized),
dd if=/dev/sda of=/dev/sdb
then go make a cup of your favourite beverage, as it takes some time if the disks are big.
Oh, and you don't want the disks to be mounted when doing that. Not the to-be-written disk at least.