halt(8) - NetBSD Manual Pages

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REBOOT(8)               NetBSD System Manager's Manual               REBOOT(8)


NAME

     reboot, poweroff, halt - restarting, powering down and stopping the sys-
     tem


SYNOPSIS

     halt [-dlnpq]
     poweroff [-dlnq]
     reboot [-dlnq]


DESCRIPTION

     The poweroff, halt and reboot utilities flush the file system cache to
     disk, send all running processes a SIGTERM, wait for several 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 enter-
     ing a shutdown record into the login accounting file and sending a mes-
     sage via syslog(3).

     The options are as follows:

     -d      Create a dump before halting or restarting.  This option is use-
             ful 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 the 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.

     -q      Do not give processes a chance to shut down before halting or
             restarting.  This option should not normally be used.

     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), shutdown(8), sync(8)


HISTORY

     A reboot command appeared in Version 6 AT&T UNIX.

     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.


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.

NetBSD 2.1                       April 4, 2003                      NetBSD 2.1