Problem scenario
You failed to use visudo on a Red Hat or Debian distribution of Linux. You try to elevate your user to sudo and run a command but you get: "jdoe is not authorized to run that command as root."
You forgot the root password. You cannot boot into rescue/recovery mode. How do you correct the /etc/sudoers file?
Solution
Run "pkexec" without quotes. If the user has sudoer privileges, it should work to gain access as root.