I am using a Ubuntu system. Today, I accidentally changed the sudoers file in /etc due to which my normal user prathmesh is not able to perform sudo operation. I don't know how to go to the root mode. I am trying "su" but it is giving me authentication failure error. Plus I don't remember setting root user's password ever.
What is the best way to solve this situation ?? Use a live CD to change the sudoers file or something else ??