Halt, power -off or reboot the machine
' shutdown 'u shutdown [OPTIONS...] [TIME] [WALL...]
shutdown may be used to halt, power -off or reboot the machine .
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 .
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 to cancel the effect of an invocation of shutdown with a time argument that is not +0 or now.
On success, 0 is returned, a non -zero failure code otherwise .