Essential System Administration, 3rd Edition

Initialization Files and Boot Scripts

This section discusses the Unix initialization files: command scripts that perform most of the work associated with taking the system to multiuser mode. Although similar activities take place under System V and BSD, the mechanisms by which they are initiated are quite different. Of the systems we are considering, FreeBSD follows the traditional BSD style, AIX is a hybrid of the two, and all the other versions use the System V scheme.

Understanding the initialization scripts on your system is a vital part of system administration. You should have a pretty good sense of where they are located and what they do. That way, you’ll be able to recognize any problems at boot time right away, and you’ll know what corrective action to take. Also, from time to time, you’ll probably need to modify them to add new services (or to disable ones you’ve decided you don’t need). We’ll discuss customizing initialization scripts later in this chapter.

Although the names, directory locations, and actual shell program code for system initialization scripts varies widely between BSD-based versions of Unix and those derived from System V, the activities accomplished by each set of scripts as a whole differs in only minor ways. In high-level terms, the BSD boot process is controlled by a relatively small number of scripts in the /etc directory, with names beginning with rc, which are executed sequentially. In contrast, System V executes a large number of scripts (as high ...