Booting and Shutting Down the System - Solaris 9 System Administrator - page 42

Keep in mind that the processes listed in the /etc/inittab file are only exe-
cuted when the system enters one of the run levels specified in the rstate
field on that entry. The default run level is defined in the /etc/inittab by
the initdefault entry. The following example shows run level 3 as the
default run level:

is:3:initdefault:
Every run level (except 4) has an entry in the /etc/inittab file that identi-
fies an rc program to execute. In addition, each run level has a directory asso-
ciated with it. This directory contains rc scripts that should be executed by
the rc program to start or stop processes and services when that run level
becomes the current one.

System Run Levels
To provide a convenient way for the system administrator to shut down or
reboot the system and control system services and resources, eight system
run levels (also referred to as init states ) are defined and assigned specific
functionality. Table 2.8 describes the eight run levels.

Table 2.8 The Eight System Run Levels

Run Level init State Functionality

0 Power Down The system is being shut down. All users are

forced off the system. All operating system serv-
ices are stopped in an orderly manner. When
complete, the system is in firmware mode. For
SPARC platforms, firmware mode is the ok
OpenBoot prompt. It is safe to turn off the power
to the system and peripherals.

s or S Single User The system is prepared for maintenance. Any

users are logged off the system. Any services
except the most basic operating system services
are stopped in an orderly manner. Any mounted
file systems remain mounted. A command-line
interface (with superuser privileges) is started
and associated with the system console. This
allows the system administrator to perform
maintenance, such as system backup, without
interference from users or applications.