SHUTDOWN(8) System Manager's Manual SHUTDOWN(8)
shutdown - close down the system at a given time
/usr/etc/shutdown [ -fhknr ] time [ warning-message ... ]
shutdown provides an automated procedure to notify users when the sys-
tem 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
At intervals that get closer as the apocalypse approaches, warning mes-
sages 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 dis-
abled by creating /etc/nologin and writing a message there. If this
file exists when a user attempts to log in, login(1) prints its con-
tents and exits. The file is removed just before shutdown exits.
At shutdown time a message is written to the system log daemon, sys-
logd(8), containing the time of shutdown, the instigator of the shut-
down, and the reason. Then a terminate signal is sent to init, which
brings the system down to single-user mode.
The time of the shutdown and the warning message are placed in
/etc/nologin, which should be used to inform the users as to when the
system will be back up, and why it is going down (or anything else).
As an alternative to the above procedure, these options can be speci-
-f Shut the system down in the manner of fasthalt (see fast-
boot(8)), so that when the system is rebooted, the file systems
are not checked.
-h Execute halt(8).
-k Simulate shutdown of the system. Do not actually shut down the
-n Prevent the normal sync(2) before stopping.
-r Execute reboot(8).
/etc/nologin tells login not to let anyone log in
/etc/xtab list of remote hosts that have mounted this host
login(1), sync(2), fastboot(8), halt(8), reboot(8), syslogd(8)
Only allows you to bring the system down between "now" and 23:59 if you
use the absolute time for shutdown.
1 July 1990 SHUTDOWN(8)