dd if=/dev/SOURCE of=/dev/DESTINATION bs=1M
I’ve found in my experience 1M tends to be a solid “bs” number; lower than that and the copy rate is slower, higher than that doesn’t give much performance gain (if any). The SOURCE should be the hard disk that has the image you want to keep and clone, the DESTINATION should be the hard disk that is to be cloned and receive the image on the SOURCE.
This will copy, bit-for-bit, everything on one hard disk to another. Useful for copying over complex workstation/server configurations on machines with the same hardware.