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System Administration Guide: Basic Administration

Run Levels

A system's run level (also known as an init state) defines what services and resources are available to users. A system can be in only one run level at a time.

The Solaris environment has eight run levels, which are described in the following table. The default run level is specified in the /etc/inittab file as run level 3.

Table 8–1 Solaris Run Levels

Run Level 

Init State 

Type 

Purpose 

0 

Power-down state 

Power-down 

 

To shut down the operating system so that it is safe to turn off power to the system.

s or S

Single-user state

Single-user 

To run as a single user with some file systems mounted and accessible.  

1 

Administrative state 

Single-user 

To access all available file systems. User logins are disabled.

2 

Multiuser state 

Multiuser 

For normal operations. Multiple users can access the system and all file system. All daemons are running except for the NFS server daemons.

3 

Multiuser level with NFS resources shared

Multiuser 

For normal operations with NFS resources shared. This is the default run level for the Solaris environment.

4 

Alternative multiuser state 

 

Currently unavailable. 

5 

Power-down state 

Power-down 

To shut down the operating system so that it is safe to turn off power to the system. If possible, automatically turns off power on systems that support this feature. 

6 

Reboot state 

Reboot 

To shut down the system to run level 0, and then reboot to multiuser level with NFS resources shared (or whatever level is the default in the inittab file).

How to Determine a System's Run Level

Display run level information by using the who -r command.


$ who -r

Use the who -r command to determine a system's current run level for any level, except run level 0.

Example—Determining a System's Run Level

This example displays information a system's current run level and information about previous run levels.


$ who -r
 .    run-level 31  Dec 13 10:102   33   04 S5
$

  1. Identifies the current run level

  2. Identifies the date of last run level change

  3. Also identifies the current run level

  4. Identifies the number of times the system has been at this run level since the last reboot

  5. Identifies the previous run level