HowTo: Reset (forgotten) root password on a Linux system
Last Update: 15.07.2009
Boot the machine with a rescue cd/dvd and once logged in and being root in the rescue system, type the following commands:
mount /dev/sda2 /mnt
mount --bind /dev/ /mnt/dev
mount -t proc proc /mnt/proc
/dev/sda2 is in this case your affected root (/) partition.