Talk:Root password recovery
From Telecomix Crypto Munitions Bureau
with newer systems, changing the hash in shadow to something that is thought to work might, in fact, not work.
provided you have physical access (or remote virtual physical access over something like iLO), boot the system from a cd (or image) containing something like knoppix, mount the / partition, and *empty* the password part in /etc/shadow. then reboot with the boot media removed, and login as root w/o a password, then change it again.