Using the init Command

The init(1M) command replaces the SunOS release 4 fasthalt command in the SunOS release 5.7 software. Use it to shut down a single-user system. You can use init to place the system in a power-down state (init 0) or into single-user state (init 1).

init Command Changes

Note the following changes to the init command:

• SunOS release 5.7 system software has eight initialization states (init states or run levels). The default init state is defined in the /etc/inittab file.

• The SunOS release 5.7 init command uses a different script for each run level instead of grouping all the run levels together in the /etc/rc, /etc/rc.boot, and /etc/rc.local files. The files, named by run level, are located in the /sbin directory.

System Administration Guide, Volume I describes this command in detail.

Changing System Run Levels

The SunOS release 5.7 init command enables you to control the run level (initialization state) of your system and move easily between various modes of operation. The SunOS release 5.7 /sbin/rc scripts control each individual run level instead of putting all system states into one file. This enables you to make changes in a unique file if you create new scripts or modify existing ones. SunOS release 4 systems controlled run levels using /etc/rc, /etc/rc.boot, and /etc/rc.local files.

The SunOS release 4 software had three run levels: PROM monitor, single user, and multiuser. These correspond to run levels 0, 1, and 3 in the SunOS release 5.7 software.

Table 8-3 gives an overview of what each run level's /sbin/rc script does.

Table 8-3 SunOS Release 5.7 System Initialization Run Levels

Run Level	Default SunOS Release 5.7 Function
0	Shuts down the system so it is safe to turn off power. Stops system services and daemons. Terminates all running processes. Unmounts all file systems.
1	Single-user (system administrator) state for tasks that allow only one user on the system. Stops system services and daemons. Terminates all running processes. Unmounts all file systems.
2	Normal multiuser operation without NFS file systems shared. Sets the timezone variable. Mounts the /usr file system. Cleans up the /tmp and /var/tmp directories. Loads the network interfaces and starts processes. Starts the cron daemon. Cleans up the uucp tmp files. Starts the lp system. Starts the sendmail daemon.
3	Normal multiuser operation of a file server with NFS systems shared. Completes all of the tasks in run level 2. Starts the NFS system daemons.
4	Alternative multiuser state (not used).
5	Shut down the system so that it is safe to remove power. If possible, automatically turn off system power on systems that support this feature.
S,s	Single-user state, running with some file systems mounted and accessible.