NAME
reboot
, poweroff
,
halt
—
restarting, powering down and stopping
the system
SYNOPSIS
halt |
[-dlnpqvxz ] |
poweroff |
[-dlnqvxz ] |
reboot |
[-dlnqvxz ] [arg ...] |
DESCRIPTION
Thepoweroff
, halt
and
reboot
utilities flush the file system cache to disk,
send all running processes a SIGTERM
, wait for up to
30 seconds for them to die, send a SIGKILL
to the
survivors and, respectively, power down, halt or restart the system. The
action is logged, including entering a shutdown record into the login
accounting file and sending a message via
syslog(3).
The options are as follows:
-d
- Create a dump before halting or restarting. This option is useful for debugging system dump procedures or capturing the state of a corrupted or misbehaving system.
-l
- Suppress sending a message via syslog(3) before halting or restarting.
-n
- Do not flush the file system cache. This option should be used with extreme caution. It can be used if a disk or a processor is on fire.
-p
- Attempt to powerdown the system. If the powerdown fails, or the system
does not support software powerdown, the system will halt. This option is
only valid for
halt
. -v
- To enable verbose messages on the console, pass the
boothowto(9) flag
AB_VERBOSE
to reboot(2). -x
- To enable debugging messages on the console, pass the
boothowto(9) flag
AB_DEBUG
to reboot(2). -z
- To silence some shutdown messages on the console, pass the
boothowto(9) flag
AB_SILENT
to reboot(2). -q
- Do not give processes a chance to shut down before halting or restarting. This option should not normally be used.
If there are any arguments passed to
reboot
they are concatenated with spaces and passed
as bootstr to the
reboot(2) system call. The string is passed to the firmware on
platforms that support it.
Normally, the shutdown(8) utility is used when the system needs to be halted or restarted, giving users advance warning of their impending doom.
SEE ALSO
reboot(2), syslog(3), utmp(5), boot(8), init(8), rescue(8), shutdown(8), sync(8)
HISTORY
A reboot
command appeared in
4.0BSD.
The poweroff
command first appeared in
NetBSD 1.5.
CAVEATS
Once the command has begun its work, stopping it before it completes will probably result in a system so crippled it must be physically reset. To prevent premature termination, the command blocks many signals early in its execution. However, nothing can defend against deliberate attempts to evade this.
This command will stop the system without running any shutdown(8) scripts. Amongst other things, this means that swapping will not be disabled so that raid(4) can shutdown cleanly. You should normally use shutdown(8) unless you are running in single user mode.
BUGS
The single user shell will ignore the
SIGTERM
signal. To avoid waiting for the timeout
when rebooting or halting from the single user shell, you have to
exec reboot
or exec
halt
.