Provided by: systemd-sysv_255.4-1ubuntu8.11_amd64 
      
    
NAME
       shutdown - Halt, power off or reboot the machine
SYNOPSIS
       shutdown [OPTIONS...] [TIME] [WALL...]
DESCRIPTION
       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.
OPTIONS
       The following options are understood:
       --help
           Print a short help text and exit.
       -H, --halt
           Halt the machine.
       -P, --poweroff
           Power the machine off (the default).
       -r, --reboot
           Reboot the machine.
       -h
           The same as --poweroff, but does not override the action to take if it is "halt". E.g.  shutdown
           --reboot -h means "poweroff", but shutdown --halt -h means "halt".
       -k
           Do not halt, power off, or reboot, but just write the wall message.
       --no-wall
           Do not send wall message before halt, power off, or 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".
       --show
           Show a pending shutdown action and time if there is any.
           Added in version 250.
EXIT STATUS
       On success, 0 is returned, a non-zero failure code otherwise.
COMPATIBILITY
       The
        shutdown command in previous init systems (including sysvinit) defaulted to single-user mode instead of
       powering off the machine. To change into single-user mode, use systemctl rescue instead.
SEE ALSO
       systemd(1), systemctl(1), halt(8), wall(1)
systemd 255                                                                                          SHUTDOWN(8)