This command attempts to write a zero at every writable location on your hard drive. Before using the command, I recommend triple checking that you are indeed erasing the correct harddrive!
Lets say that /dev/sda is the hdd we wish to clone, and that /dev/sdb is an empty drive that is to be used as the target.
Note : the destination harddrive should be equal or larger in size to the source harddrive.
Backup : dd if=/dev/sda of=/backup/mbr.bkp bs=512 count=1 Restore : dd if=/backup/mbr.bkp of=/dev/sda bs=512 count=1
Backup : dd if=/dev/sda of=/backup/mbr.bkp bs=446 count=1 Restore : dd if=/backup/mbr.bkp of=/dev/sda bs=446 count=1