shutdown - bring the system down

shutdown brings the system down in a secure way.  All logged-in users
are notified that the system is going down, and  login(1)  is  blocked.
It is possible to shut the system down immediately or after a specified
delay.  All processes are first notified that the system is going  down
by the signal SIGTERM.  This gives programs like vi(1) the time to save
the file being edited, mail and news processing programs  a  chance  to
exit  cleanly,  etc.   shutdown  does  its  job  by signalling the init
process, asking it to change the runlevel.  Runlevel 0 is used to  halt
the  system, runlevel 6 is used to reboot the system, and runlevel 1 is
used to put to system into a state where administrative  tasks  can  be
performed; this is the default if neither the -h or -r flag is given to
shutdown.  To see which actions are taken on halt  or  reboot  see  the
appropriate entries for these runlevels in the file /etc/inittab.

/sbin/shutdown [-akrhPHfFnc] [-t sec] time [warning message]

halt, reboot, poweroff - stop the system.

Halt  notes  that  the  system  is  being  brought  down  in  the  file
/var/log/wtmp, and then either tells the  kernel  to  halt,  reboot  or
power-off the system.

If  halt or reboot is called when the system is not in runlevel 0 or 6,
in other words when it's running normally,  shutdown  will  be  invoked
instead  (with  the  -h  or -r flag). For more info see the shutdown(8)
manpage.

The rest of this manpage describes the behaviour in runlevels 0 and  6,
that is when the systems shutdown scripts are being run.


/sbin/halt [-n] [-w] [-d] [-f] [-i] [-p] [-h]
/sbin/reboot [-n] [-w] [-d] [-f] [-i]
/sbin/poweroff [-n] [-w] [-d] [-f] [-i] [-h]