Watchdog
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A watchdog timer or Watchdog is a hardware implemented monitoring circuit for a system hang.
It is a timer built on a separate comparator chip. The timer is periodically reset by sending an alternating signal to the timer input from the GPIO output of the processor.
If the reset does not occur within a certain time interval (~15c), a power reset occurs (turning off one of the power lines for 3-4 seconds).
In the system watchdog device is presented by the /dev/watchdog1, the configuration of the watchdog daemon is stored in the file /etc/watchdog.conf