SHUTDOWN(8)

NAME
shutdown, poweroff - close down the system at a given time

SYNOPSIS
shutdown [-] [ -c | -f | -h | -p | -r | -k] [ -o [-n]] [-q] time [warning-message ...]
poweroff

DESCRIPTION
The shutdown utility provides an automated shutdown procedure for super-users to nicely notify users when the system is shutting down, saving them from system administrators, hackers, and gurus, who would otherwise not bother with such niceties. In order to use the shutdown command, the user must have root privileges or be a member of the operator group.

The following options are available:

-c  The system is power cycled (power turned off and then back on) at the specified time. If the hardware doesn't support power cycle, the system will be rebooted. At the present time, only systems with BMC supported by the ipmi(4) driver that implement this functionality support this flag. The amount of time the system is off is dependent on the device that implements this feature.

-f  The shutdown command ignores the presence of the /var/run/noshutdown file.

-h  The system is halted at the specified time.

-p  The system is halted and the power is turned off (hardware support required, otherwise the system is halted) at the specified time.

-r  The system is rebooted at the specified time.

-k  Kick everybody off. The -k option does not actually halt the system, but leaves the system multi-user with logins disabled (for all but super-user).

-o  If one of the -c, -h, -p, or -r options is specified, shutdown will execute halt(8) or reboot(8) instead of sending a signal to init(8).

-n  If the -o option is specified, prevent the file system cache from being flushed by passing -n to halt(8) or reboot(8). This option should probably not be used.

-q  Shut down quietly. Suppress the warning message to all logged in users about system shutdown. It is an error to supply a warning-message when warnings are suppressed.

time
    Time is the time at which shutdown will bring the system down and may be the case-insensitive word now (indicating an immediate shutdown) or a future time in one of two formats: +number or an absolute time specification. The first form brings the system down in number time units (defaulting to minutes), and the second at the absolute time specified.

    An absolute time may be specified in one of the following formats, where unspecified parts default to the current date:

    hhmm
        Hour and minute.

    DDhhmm
        Day, hour, and minute.

    MMDDhhmm
        Month, day, hour, and minute.

    YYMMDDhhmm
        Year (within the century), month, day, hour, and minute.

    The year YY is interpreted relative to the current century, with a one-year tolerance for values slightly in the past (to accommodate entry at year boundaries). +number may be specified in units other than minutes by appending the corresponding suffix: “s”, “sec”, “secs”, “m”, “min”, “mins”, “h”, “hour”, “hours”. The unit suffixes are case-insensitive.

    If an absolute time is specified, but not a date, and that time today has already passed, shutdown will assume that the same time tomorrow was meant. (If a complete date is specified which has already passed, shutdown will print an error and exit without shutting the system down.)

warning-message
    Any other arguments comprise the warning message that is broadcast to users currently logged into the system.

-   If ‘-’ is supplied as an option, the warning message is read from the standard input.

At intervals, becoming more frequent as apocalypse approaches and starting at ten hours before shutdown, warning messages are displayed on the terminals of all users logged in. Five minutes before shutdown, or immediately if shutdown is in less than five minutes, logins are disabled by creating /var/run/nologin and copying the warning message there. If this file exists when a user attempts to log in, login(1) prints its contents and exits. The file is removed just before shutdown exits.

At shutdown time a message is written to the system log, containing the time of shutdown, the person who initiated the shutdown and the reason. The corresponding signal is then sent to init(8) to respectively halt, reboot, or bring the system down to single-user state (depending on the above options). The time of the shutdown and the warning message are placed in /var/run/nologin and should be used to inform the users about when the system will be back up and why it is going down (or anything else).

A scheduled shutdown can be canceled by killing the shutdown process (a SIGTERM should suffice). The /var/run/nologin file that shutdown created will be removed automatically.

If the /var/run/noshutdown file is present, shutdown exits without executing any action on the system.

When run without options, the shutdown utility will place the system into single-user mode at the time specified.

Calling “poweroff” is equivalent to running:

    shutdown -p now

FILES
/var/run/nologin
    tells login(1) not to let anyone log in.
/var/run/noshutdown
    prevents shutdown from initiating an action on the system. Can be overridden with the -f option.

EXAMPLES
Reboot the system in 30 minutes and display a warning message on the terminals of all users currently logged in:

    # shutdown -r +30 "System will reboot"

Halt the system at 23:30 (using either format):

    # shutdown -h 2330
    # shutdown -h 23:30

Power off the system on June 15th at 10:00:

    # shutdown -p 06151000

COMPATIBILITY
The hours and minutes in any absolute time format may be separated by a colon (``:'') for backward compatibility. For example, hh:mm is accepted as equivalent to hhmm.

SEE ALSO
kill(1), login(1), wall(1), nologin(5), halt(8), init(8), reboot(8)

HISTORY
A shutdown command was originally written by Ian Johnstone for UNSW's modified AT&T UNIX 6th Edn. It was modified and then incorporated in 4.1BSD.