shutdown — Halt, power-off or reboot the machine
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¶-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".