root password

Beaglebone out of the box. Base system. I changed the root password and after rebooting I can not log
back in as root.

Tried the standard default and it does not work either.

How can I reset the system back to the way it was ??

Thanks for any help you have,

The best option is just to 'reflash' or edit /boot/uEnv.txt add add
the "single" and use your linux fuu..