When something goes wrong with your Linux-based system, you can try to diagnose it yourself with the many troubleshooting tools bundled with the operating system. Knowing about these tools, and how to effectively use them, can help you overcome many of the common problems on your system. Here's a list of some of the weapons in your arsenal against Linux problems.
CLI Magic: Linux troubleshooting tools 101
CLI Magic: Linux troubleshooting tools 101