Re: <USER> is not in the sudoers file. This incident will be reported.
To explain: On a dual-boot system, the GRUB menu appears on startup. On a single-boot system, you hold down the Shift key while starting up and it brings up the GRUB menu.
Originally Posted by CharlesA
You'll see a list of installed kernels. Basically, you choose the second one in the list - it'll have "Recovery Mode" in its name. Then you can just run:
and change back whatever you changed.
You've learnt the hard way: It's not a good idea to mess with the security system. You're just setting up your system at the moment which is why you get a fair few authentication dialogs and why they seem annoying at first. Once you've set up your system, you'll rarely get them anyway.
Making the modification you described doesn't remove all authentication dialogs anyway. It just stops the 'gksudo' ones from appearing. Any related to Policykit, such as Software Center or Gnome authentication dialogs, will continue to appear. Can't be stopped either as far as I know; you really don't want to because things will probably break, or you'll loosen your computer's security to the point where a script kiddie will 0wn your computer. If you're going to make your computer insecure, you might as well do it the quick way and install Windows XP.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.