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WDOGCTL(8)                BSD System Manager's Manual               WDOGCTL(8)

NAME
     wdogctl -- Watchdog timer control utility

SYNOPSIS
     wdogctl
     wdogctl -k [-A] [-p seconds] timer
     wdogctl -u [-A] [-p seconds] timer
     wdogctl -d

DESCRIPTION
     wdogctl is used to manipulate watchdog timers.  Watchdog timers provide a
     means of ensuring that a system continues to make progress.  This is
     accomplished by use of a timer, provided by either hardware or software;
     when the timer expires, the watchdog resets the system.  In this case of
     a hardware watchdog timer, this is accomplished by asserting the system's
     hardware reset signal.  In the case of a software watchdog timer, this is
     accomplished by calling the kernel's normal reboot path.  In order to
     prevent the system from rebooting, something must refresh the timer to
     prevent it from expiring.

     The NetBSD kernel provides two basic modes in which watchdog timers may
     operate: kernel tickle mode and user tickle mode.  In kernel tickle mode,
     a timer in the kernel refreshes the watchdog timer.  In user tickle mode,
     wdogctl runs in the background and refreshes the watchdog timer.  In ker-
     nel tickle mode, progress of the kernel is ensured.  In user tickle mode,
     the ability for user programs to run within a known period of time is
     ensured.  Note that user tickle mode must be used with caution; on a
     heavily loaded system, the timer may expire accidentally, even though
     user programs may be making (very slow) progress.

     In both modes, an attempt is made to refresh the watchdog timer in one
     half the timer's configured period.  That is, if the watchdog timer has a
     period of 30 seconds, a refresh attempt is made every 15 seconds.

     If called without arguments, wdogctl will list the timers available on
     the system.  When arming a watchdog timer, the timer argument is the name
     of the timer to arm.

     Only one timer may be armed at a time; if an attempt is made to arm a
     timer when one is already armed, an error message will be displayed and
     no action will be taken.

     The options are as follows:

     -k      Arm timer in kernel tickle mode.

     -u      Arm timer in user tickle mode.

     -A      When arming a timer, this flag indicates that an audible alarm is
             to sound when the watchdog timer expires and resets the system.
             If the selected timer does not support an audible alarm, this
             option will be silently ignored.

     -p period
             When arming a timer, this flag configures the timer period to
             period seconds.  If the specified period it outside the timer's
             range, an error message will be displayed and no action will be
             taken.

     -d      This flag disarms the currently active timer.  Note that not all
             watchdog timers can be disabled once armed.  If the selected
             timer can not be disabled, an error message will be displayed and
             the timer will remain armed.

FILES
     /dev/watchdog -- the system monitor watchdog timer device

SEE ALSO
     envsys(4), envstat(8)

HISTORY
     The wdogctl command first appeared in NetBSD 1.5.1.

AUTHORS
     The wdogctl command and the NetBSD watchdog timer framework were written
     by Jason R. Thorpe <thorpejATzembu.com>, and contributed by Zembu Labs,
     Inc.

BSD                              July 29, 2002                             BSD