If you want only to reset the root password, you can do the following:
In GRUB loader type “e” on the default start item, find the line where it says “linux” and append
this to the end of the line : “init=/bin/bash”
Press ctrl-x to boot.
When you get the prmpt type:
mount -rw -o remount /
You have now enabled read access.
Type the password you want twice, and it will reply with OK, after this you can boot as normal with the new root password. 🙂