Even a site with a small network of computers is likely to have hundreds of configuration files. The content of these files determines how the overall system works and what it does; this is what makes the difference between a lab of student machines and the same set of hardware providing a Web service. Working out what to put in the configuration files takes a lot of skill and experience. Any mistakes are likely to cause some kind of failure or security breach. A system administrator will usually be responsible for setting these files up correctly and updating them as the system and the...