The watchdog program can be used as a powerful software watchdog daemon
or may be alternately used with a hardware watchdog device such as the
IPMI hardware watchdog driver interface to a resident Baseboard
Management Controller (BMC). watchdog periodically writes to /dev/watchdog;
the interval between writes to /dev/watchdog is configurable through settings
in the watchdog sysconfig file. This configuration file is also used to
set the watchdog to be used as a hardware watchdog instead of its default
software watchdog operation. In either case, if the device is open but not
written to within the configured time period, the watchdog timer expiration
will trigger a machine reboot. When operating as a software watchdog, the
ability to reboot will depend on the state of the machine and interrupts.
When operating as a hardware watchdog, the machine will experience a hard
reset (or whatever action was configured to be taken upon watchdog timer
expiration) initiated by the BMC.