If you just want enough information to fix your problem quickly, you can read the How-To section of this post and skip the rest. I would highly recommend reading everything though, as a good understanding of the concepts and commands outlined here will serve you well in the future. We also have Video and Audio included with this post that may be a good quick reference for you. Don’t forget that the man and info pages of your Linux/Unix system can be an invaluable resource as well when you’re trying to solve problems.