NAME

shutdown − close down the system at a given time

SYNOPSIS

/etc/shutdown [−k] [−r] [−h] [−f] [−n] time [warning-message ...]

DESCRIPTION

The shutdown command provides an automated shutdown procedure for the super-user to notify users when the system is shutting down.  The time argument specifies when shutdown will bring the system down; it may be the word now (indicating an immediate shutdown), or it may specify a future time in one of two formats: +number and hour:minute.  The first form brings the system down in number minutes, and the second brings the system down at the time of day indicated in 24-hour notation. 

At intervals that get smaller as the system shutdown approaches, warning messages are displayed at terminals of all logged-in users, and of users who have remote mounts on that machine.  Five minutes before shutdown, or immediately if shutdown is in less than 5 minutes, logins are disabled by creating the file /etc/nologin and writing a message there.  If this file exists when a user attempts to log in, login prints its contents and exits.  The file is removed just before shutdown exits. 

At shutdown time a message is written in the system log, containing the time of shutdown, who ran shutdown and the reason.  The script /etc/rc.shutdown is called with the argument warn. A terminal stop signal is sent to init, so that processes are not respawned as they die.  If −r, −n, or −k, was used, then shutdown will exec reboot(8), halt(8), or avoid shutting the system down (respectively).  Otherwise shutdown sends all remaining non-system processes a sigterm signal, then calls /etc/rc.shutdown with the argument shutdown. Finally, it sends a terminate signal to init, which brings the system down to single-user mode. 

The option −k is to make people think the system is going down, but does not actually take it down. 

With the −f option, shutdown arranges, in the manner of fastboot(8), that when the system is rebooted the file systems will not be checked. 

The −n option prevents the normal sync(2) before stopping. 

The time of the shutdown and the warning message are placed in the file /etc/nologin, which should be used to tell the users when the system will be back up, and why it is going down.

FILES

/etc/nologin tells login not to let anyone log in
/etc/rmtab list of remote hosts that have mounted this host
/etc/rc.shutdown system shutdown script

SEE ALSO

login(1), reboot(8), rc(8), init(8), halt(8), fastboot(8)

BUGS

Shutdown only allows you to kill the system between now and 23:59 if you use the absolute time for shutdown. 

The disks will still be synced even if -n option is given if the rc.shutdown script runs commands that sync the disks (such as umount(8)). 

4BSD