If you're adding/removing yourself from a group in Linux, you may find yourself in this situation when you try to run <b>sudo</b>:
$ sudo aptitude remove <program> <user> is not in the sudoers file. This incident will be reported.
Reported? To whom? To spite Big Brother, run these commands:
$ su root $ usermod -a -G admin <user>
You're now added to the <b>admin</b> group and have <b>sudo</b> rights again. References: <a href="http://www.cyberciti.biz/faq/howto-linux-add-user-to-group">Add User to Group</a>