shutdown(8) — Linux manual pages

Linux manual pages	Section 8

Name

shutdown — close down the system

Synopsis

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]

DESCRIPTION

In general, shutdown prepares the system for a power down or reboot. A absolute or delta time can be given, and periodic messages will be sent to all users warning of the shutdown. If no message is specified on the command line, shutdown will ask for a message to be sent, unless the −q option is set.

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.

Prior to unmounting all discs, the SIGQUIT signal is sent to the init process, which will in turn exec shutdown(8). This allows for clean unmounting, even if the old inode for the init process was unlinked. If the current process ID (PID) equals 1, then shutdown(8) will pause forever.

OPTIONS

−h: Halt the system. Do not reboot. This option is used when powering down the system.
−r: Reboot the system.
−f: Fast. When the system is rebooted, the file systems will not be checked. This is arranged by creating /fastboot, which /etc/rc must detect (and delete).
−q: Quiet. This uses a default broadcast message, and does not prompt the user for one.
−s: Reboot in single user mode. This is arranged by creating /etc/singleboot, which simpleinit(8) detects (and deletes).

FILES

/etc/rc
/fastboot
/etc/singleboot
/etc/nologin
/var/log/wtmp
/etc/shutdown.conf

CONFIG

The configuration file /etc/shutdown.conf is used to determine the action to take when halting the machine. The currently supported file format is extremely primitive. The first line must contain two strings separated by whitespace. The first string must be HALT_ACTION and the second specifies the action you wish to take on halt. The options allowed are:

halt: This will simply halt the system. This is the default behaviour. Note also that this is the fallback if another option fails.
power_off: This will use the kernel power shutdown facility. This is usually only available on machines with Advanced Power Management (APM).
programname: This specifies a command to run to shut down the power. The first character must be a "/". Bear in mind that this command will be run with only the root filesystem mounted (and it will be read-only), and no daemons running.

BUGS

Unlike the BSD shutdown, users are notified of shutdown only once or twice, instead of many times, and at shorter and shorter intervals as "apocalypse approaches." Some would construe this as a feature.

AUTHOR

This page documents the version of shutdown originally written by Peter Orbaek ([email protected]).