shutdown is executed by the super user to change the state of the machine. In most cases, it is used to change from the multi-user state (state 2) to another state.

By default, shutdown brings the system to a state where only the console has access to the operating system. This state is called single-user.

Before starting to shut down daemons and killing processes, shutdown sends a warning message and, by default, a final message asking for confirmation. message is a string that is sent out following the standard warning message "The system will be shut down in ..." If the string contains more than one word, it should be contained within single (') or double (") quotation marks.

The warning message and the user provided message are output when there are 7200, 3600, 1800, 1200, 600, 300, 120, 60, and 30 seconds remaining before shutdown begins. See EXAMPLES.

System state definitions are:

state 0

Stop the operating system.

state 1

State 1 is referred to as the administrative state. In state 1 file systems required for multi-user operations are mounted, and logins requiring access to multi-user file systems can be used. When the system comes up from firmware mode into state 1, only the console is active and other multi-user (state 2) services are unavailable. Note that not all user processes are stopped when transitioning from multi-user state to state 1.

state s, S

State s (or S) is referred to as the single-user state. All user processes are stopped on transitions to this state. In the single-user state, file systems required for multi-user logins are unmounted and the system can only be accessed through the console. Logins requiring access to multi-user file systems cannot be used.

state 5

Shut the machine down so that it is safe to remove the power. Have the machine remove power, if possible. The rc0 procedure is called to perform this task.

state 6

Stop the operating system and reboot to the state defined by the initdefault entry in /etc/inittab. The rc6 procedure is called to perform this task.

-y

Pre-answer the confirmation question so the command can be run without user intervention.

-g grace-period

Allow the super user to change the number of seconds from the 60-second default.

-i init-state

If there are warnings, init-state specifies the state init is to be in. By default, system state `s' is used.

/etc/inittab

controls process dispatching by init

See attributes(5) for descriptions of the following attributes:

boot(1M), halt(1M), init(1M), killall(1M), reboot(1M), ufsdump(1M), init.d(4), inittab(4), nologin(4), attributes(5)

When a system transitions down to the S or s state, the /etc/nologin file (see nologin(4)) is created. Upon subsequent transition to state 2 (multi-user state), this file is removed by a script in the /etc/rc2.d directory.