wdogctl(8) - NetBSD Manual Pages

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


NAME

     wdogctl -- Watchdog timer control utility


SYNOPSIS

     wdogctl
     wdogctl -d
     wdogctl -e [-A] [-p seconds] timer
     wdogctl -k [-A] [-p seconds] timer
     wdogctl -t
     wdogctl -u [-A] [-p seconds] timer
     wdogctl -x [-A] [-p seconds] timer


DESCRIPTION

     wdogctl is used to manipulate watchdog timers.  A watchdog timer is a
     hardware or software timer that resets the system if it fails to make
     progress within a prescribed period.  To prevent the system from being
     reset, something must refresh the timer to prevent it from expiring.

     A hardware watchdog timer asserts system's hardware reset signal when it
     expires.  A software watchdog timer calls the kernel's s normal reboot
     path.

     The NetBSD kernel provides three modes in which watchdog timers may oper-
     ate: kernel tickle mode, user tickle mode, and external tickle mode.

     kernel tickle mode
                   A timer in the kernel refreshes the watchdog timer.  This
                   ensures kernel threads can make progress within the period
                   of the watchdog timer.

     user tickle mode
                   wdogctl runs in the background and refreshes the watchdog
                   timer.  This ensures user programs can make progress within
                   the period of the watchdog timer.

                   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.  A user-mode timer is disarmed (if possible) when
                   the device is closed, unless the timer is activated with
                   the -x option.

     external tickle mode
                   Similar to user tickle mode, except that the tickle must be
                   done explicitly by a separate invocation of wdogctl -t.
                   This allows users to determine the activity whose progress
                   the watchdog timer checks.

     In kernel and user tickle modes, an attempt is made to refresh the watch-
     dog timer in one half the timer's configured period.  For example, 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:

     -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 audi-
                 ble alarm, this option will be silently ignored.

     -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.

     -e          Arm timer in external tickle mode.

     -k          Arm timer in kernel tickle mode.

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

     -t          This flag tickles an external mode timer.

     -u          Arm timer in user tickle mode.

     -x          Arm timer in a modified user tickle mode: closing the device
                 will not disarm the timer.


FILES

     /dev/watchdog  the system monitor watchdog timer device


SEE ALSO

     acpiwdrt(4), evbarm/iopwdog(4), i386/elansc(4), i386/gcscpcib(4),
     i386/geodewdog(4), ipmi(4), itesio(4), pcweasel(4), pwdog(4), swwdog(4),
     x86/tco(4)


HISTORY

     The wdogctl command first appeared in NetBSD 1.6.


AUTHORS

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

NetBSD 10.99                     July 11, 2020                    NetBSD 10.99