I have Ubuntu 10.04. Certain operations in the Terminal application or operations require me to type sudo [whatever command] and my password. I have noticed the effects of sudo last for awhile; five minutes or so.
How can I explicitly exit sudo and go back to being me at the command prompt?
sudo -k
Note that you're not running sudo to need to exit it, rather sudo remembers the last time you authenticated and doesn't require re-authentication if that's recent enough. This command will reset timestamp to the epoch. You can change the timeout value in the system configuration file: man sudoers.