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. 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 operate: 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
- wdogctlruns 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 - -xoption.
 
- 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
    watchdog 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 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/tco(4)
Thewdogctl 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.