TITLE    : Recovering the root password on a Linux system
OS LEVEL : Linux (any version)
DATE     : 27/11/2003
VERSION  : 1.0
AUTHOR   : Hubertus A. Haniel (hubba@unixcook.com)
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This will obviously only work if there is no boot loader password set:

During the boot in grub or lilo add the option "init=/bin/bash".
This will boot your system straight into bash and use the shell as init which 
means if you drop out of the shell the system will panic and init levels do not
work. It will also mean that your root filesystem is most likely mounted in read
only mode so the following commands will have to be executed to reset the root
password:

mount -o remount,rw /          (Remount root in read-write)
passwd root                    (reset the password)
sync;sync;sync                 (sync the disk)
exit  

You will now have to power cycle the box and you will be able to login as root
again ;)