Customizing UNIX system startup

Customizing UNIX system startup

When your system is switched on and booted, certain aspects of the UnixWare^® 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:

set initial run levels
set the system clock
enable terminals
start programs
check and mount specified filesystems
clean up temporary directories
set home directories and terminal types for users
display system messages

The files discussed here are /etc/inittab, the scripts in the /etc/rc* directories, 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 one of the /etc/rc* directories, 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 inittab(4). For more information on init run levels, refer to init(1M). The scripts in /etc/rc* and the .profile and .login files contain Bourne shell commands and comments. See ``Shell programming'' for more information on shell programming.