Chapter 14: ETC

Overview

You are in a maze
Of twisty little configs
No two are alike

The /etc directory is the heart of any UNIX-like operating system. /etc contains the files that tell the system how it works, what it does, and how it behaves under any circumstances. The first thing I do on any unfamiliar UNIX breed is check out the /etc directory and see what make it tick; it's like kicking the tires and checking under the hood of a used car before taking it for a test drive.

If you've never done this before, I highly recommend sitting down and reading the contents of /etc of almost any UNIX system. This is one of the best ways to earn your journeyman grade in systems administration. If you can read everything in /etc and explain what it does, you have a good grip on the next rung up in the professional ladder.

Understanding /etc is especially important when upgrading OpenBSD, as /etc must be updated to include files and entries from the new version. In many cases the contents of existing files change, so you must understand what the files do in order to make proper decisions on what should be edited and what should be completely replaced. While mergemaster(8) will help identify files that have been added or changed, the actual decision-making process cannot be automated.

You won't find every single file in /etc discussed in this chapter. OpenBSD supports a wide variety of functions, and many of them have configuration files in /etc. We are going to discuss in depth the general-purpose files that are in use in almost every system, however, as well as some files that System V and Linux users probably haven't encountered before.

Some files are used for specific subsystems that we don't cover in this book. For example, /etc/exports is used for NFS. Thick books have been written about NFS, and any overview I could provide within this chapter would be incomplete. If you've set up NFS, however, you already know about /etc/exports, and you'll know that if you overwrite it during an upgrade you'll be restoring from backup later that day. Files like this are mentioned, but only with a brief description and a pointer to further information.

Similarly, files that are discussed in other chapters are only mentioned, and a pointer is provided to the chapter.