What should I do to set root password

I forgot set a root password for system,so I can not be able to login as root user.I have tried to re-set root password using rescue CD and floppy,and command "chroot /mnt/sysimage".But it is not work. I didn't find the interface and commands for changing root password.What should I do?

Please try to keep your discussion in one place. The other thread on this very same topic is here:
http://www.linuxquestions.org/questi...hreadid=332050

I will post my response there.