NAME
reboot,
poweroff,
halt
—
restarting, powering down and stopping the
system
SYNOPSIS
reboot |
[-dlnqvxz]
[arg ...] |
DESCRIPTION
The
poweroff,
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.