Solaris init states refer to the services provided by the system. The exact services and processes run at each init level are determined by the scripts in the /etc/rc#.d directories. The default service levels for each init state are:
- 0: The system is at the security monitor (>) prompt. It is safe to shut down the system when it is at this init state.
- 1, s or S: This state is known as "single-user" or "system administrator" mode. Root is the only user on the system, and only basic kernel functions are enabled. A limited number of filesystems (usually only root and /usr) are mounted. This init state is often used for sensitive functions (such as kernel libc patches) or while troubleshooting a problem that is keeping the system from booting into multiuser mode.
- 2: Multiple users can log in. Most system services (except for NFS server and printer resource sharing) are enabled.
- 3: Normal operating state. NFS and printer sharing is enabled, where appropriate.
- 4: Usually undefined.
- 5: Associated with the boot -a command. The system is taken to init 0 and an interactive boot is started.
- 6: Reboot. This state takes the system to init state 0 and then to the default init state (usually 3, but can be redefined in the /etc/inittab file).
To get to a desired run level n, each of the rc (run control) scripts from 1 to n is run. To get to run level 0, the K scripts are run in each rc#.d directory between the current run level and 0 in reverse numerical order.