In it's simplest definition watchdog is a hardware and/or software timer-register which can used to trigger an system reset or action if something doesn’t works as expected. The watchdog timer performs regular heartbeat checks and if failed performs the pre-defined corrective tasks.

The now hugely popular mini-computer Raspberry Pi features the BCM2835 SoC which has an built-in hardware watchdog timer, this can be used to check tasks like network connectivity, system load, system freeze and other metrics like temperature to perform corrective measures like automatic system reset. Just follow the steps as instructed next to get started with using watchdog timer.