5. /etc: Configuration Files

/etc is one of UNIX® systems' most essential directories because it contains all the host-specific configuration files. Never delete it to save space! Likewise, if you want to extend your tree structure over several partitions, remember that /etc must not be put on a separate partition: it is needed for system initialization and must be on the root partition at boot time.

Here are some important files:

Certain sub-directories exist for programs which require a large number of configuration files. This applies to the X Window System, for example, which stores all of its configuration files in the /etc/X11 directory.