wdogctl —
Watchdog timer control utility
  
    | wdogctl | -e[-A]
      [-pseconds]
      timer | 
  
    | wdogctl | -k[-A]
      [-pseconds]
      timer | 
  
    | wdogctl | -u[-A]
      [-pseconds]
      timer | 
  
    | wdogctl | -x[-A]
      [-pseconds]
      timer | 
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 three basic
    modes in which watchdog timers may operate: kernel tickle mode, user tickle
    mode, and external 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 kernel 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. A user-mode timer is disarmed
    (if possible) when the device is closed, unless the timer is activated with
    the -x option.
External-mode watchdogs are similar to user-mode watchdogs, except
    that the tickle must be done explicitly by a separate invocation of the
    program with the -t option.
In the first two 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:
  - -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.
- -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.
- -pperiod
- 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.
 
/dev/watchdog -- the system monitor watchdog timer
  device
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/ichlpcib(4)
The wdogctl command first appeared in
  NetBSD 1.6.
The wdogctl command and the
  NetBSD watchdog timer framework were written by
  Jason R. Thorpe ⟨thorpej@zembu.com⟩, and
  contributed by Zembu Labs, Inc.