shutdown [ -h | -r ] [ -fqs ] [ now | hh:ss | +mins ] [ message ] reboot [ -h | -r ] [ -fqs ] [ now | hh:ss | +mins ] [ message ] fastboot [ -h | -r ] [ -fqs ] [ now | hh:ss | +mins ] [ message ] halt [ -h | -r ] [ -fqs ] [ now | hh:ss | +mins ] [ message ] fasthalt [ -h | -r ] [ -fqs ] [ now | hh:ss | +mins ] [ message ] The current cLIeNUX command itself says.... $Usage: shutdown [-krhfnc] [-t secs] time [warning message] -k: don't really shutdown, only warn. -r: reboot after shutdown. -h: halt after shutdown. -f: do a 'fast' reboot (skip fsck). -F: Force fsck on reboot. -n: do not go through "init" but go down real fast. -c: cancel a running shutdown. -t secs: delay between warning and kill signal. ** the "time" argument is mandatory! (try "now") ** HHmmm. No -q.
halt is the same as shutdown -h -q now
fasthalt is the same as shutdown -h -q -f now
reboot is the same as shutdown -r -q now
fastboot is the same as shutdown -r -q -f now
The default delta time, if none is specified, is 2 minutes.
Five minutes before shutdown (or immediately, if shutdown is less than five minutes away), the /etc/nologin file is created with a message stating that the system is going down and that logins are no longer permitted. The login (1) program will not allow non-superusers to login during this period. A message will be sent to all users at this time.
When the shutdown time arrives, shutdown notifies all users, tells init(8) not to spawn more getty(8)'s, writes the shutdown time into the /var/log/wtmp file, kills all other processes on the system, sync(2)'s, unmounts all the disks, sync(2)'s again, waits for a second, and then either terminates or reboots the system.
/etc/rc /fastboot /etc/singleboot /etc/nologin /var/log/wtmp