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Chapter 12 # Watchdog Timer For information about how the Watchdog Timer guards against operating system hang, see the following sections: The `nhwdt` Daemon Monitoring by the Daemon Monitor ## The `nhwdt` Daemon Low-level system monitoring in the Foundation Services is provided by the Watchdog Timer service. This service is implemented by the `nhwdtd` daemon. The Watchdog Timer service monitors the hardware watchdog on the nodes of the cluster, at the lights-off management (LOM) level. The `nhwdtd` daemon monitors a node for operating system hang, but does not monitor the boot process. Hardware watchdogs that operate at the OpenBoot™ PROM (OBP) level are monitored by the platform's software, not by the `nhwdtd` daemon. For information about which hardware is monitored at the OBP level and the LOM level, see "Types of Hardware Watchdogs" in the Netra High Availability Suite Foundation Services 2.1 6/03 Hardware Guide. The Watchdog Timer can be configured differently on each peer node depending on your requirements. For information about how to configure the Watchdog Timer, see the `nhfs.conf`(4) man page. ## Monitoring by the Daemon Monitor The Watchdog Timer is monitored by the Daemon Monitor. If the `nhwdtd` daemon fails, it is relaunched three times. If the `nhwdtd` daemon fails a third time, the node is rebooted. The `nhwdtd` daemon operates at a lower priority than the `nhpmd` daemon, but at a higher priority than the other Foundation Services daemons.
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