/usr/ucb/shutdown [-fhknr] time [warning-message...]
shutdown provides an automated procedure to notify users when the system is to be shut down. time 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:min. 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 closer as the apocalypse approaches, warning messages are displayed at terminals of all logged-in users, and of users who have remote mounts on that machine.
At shutdown time a message is written to the system log daemon, syslogd(1M), containing the time of shutdown, the instigator of the shutdown, and the reason. Then a terminate signal is sent to init, which brings the system down to single-user mode.
As an alternative to the above procedure, these options can be specified:
-f Arrange, in the manner of fastboot(1B), that when the system is rebooted, the file systems will not be checked.
-h Execute halt(1M).
-k Simulate shutdown of the system. Do not actually shut down the system.
-n Prevent the normal sync(2) before stopping.
-r Execute reboot(1M).
/etc/rmtab remote mounted file system table
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
fastboot(1B), login(1), halt(1M), reboot(1M), syslogd(1M), sync(2), rmtab(4), attributes(5)
Only allows you to bring the system down between now and 23:59 if you use the absolute time for shutdown.