SHUTDOWN

The first argument may be a time string (which is usually "now"). Optionally, this may be followed by a wall message to be sent to all logged-in users before going down.

The time string may either be in the format "hh:mm" for hour/minutes specifying the time to execute the shutdown at, specified in 24h clock format. Alternatively it may be in the syntax "+m" referring to the specified number of minutes m from now. "now" is an alias for "+0", i.e. for triggering an immediate shutdown. If no time argument is specified, "+1" is implied.

Note that to specify a wall message you must specify a time argument, too.

If the time argument is used, 5 minutes before the system goes down the /run/nologin file is created to ensure that further logins shall not be allowed.  

OPTIONS

The following options are understood:

–help

Print a short help text and exit.

-H, –halt

Halt the machine.

-P, –poweroff

Power-off the machine (the default).

-r, –reboot

Reboot the machine.

-h

Equivalent to –poweroff, unless –halt is specified.

-k

Do not halt, power-off, reboot, just write wall message.

–no-wall

Do not send wall message before halt, power-off, reboot.

-c

Cancel a pending shutdown. This may be used cancel the effect of an invocation of shutdown with a time argument that is not "+0" or "now".

EXIT STATUS

On success, 0 is returned, a non-zero failure code otherwise.