System Administration Guide
Appendix A, Customizing UNIX system startup

Appendix A

Appendix A<P> Customizing UNIX system startup Customizing UNIX system startup

When your system is switched on and booted, certain aspects of the UNIX system operation are set up. The system reads initialization files at startup, when changing run levels, and whenever a user logs in. By modifying these files, you can adapt system startup. 

The system initialization files contain commands or data that:

The files discussed here are /etc/inittab, the scripts in the /etc/rc2.d directory, the .profile, .cshrc, and .login files (along with their system-wide counterparts in /etc), and the /etc/motd file. 

The system administrator can modify the startup files to create any initial system and user environment. For example, by adding or changing entries in the inittab file, specific terminals can be enabled (or disabled) when the system enters or leaves a particular run level. By changing a script in the /etc/rc2.d directory, process accounting can be started automatically at system startup. The administrator can also customize a specific user's environment by modifying the .profile or .login file in their home directories.

The initialization files are ordinary text files and can be modified using a text editor. Entries in the /etc/inittab file must follow a specific format described in the inittab(F) manual page. For more information on init run levels, refer to the init(M) manual page. The scripts in /etc/rc2.d and the .profile and .login files contain Bourne shell commands and comments. See Chapter 11, ``Automating frequent tasks'' in the Operating System User's Guide for more information on shell programming.