Date: Tue, 05 May 2009 15:06:59 -0600 From: Brad Waite <freebsd@wcubed.net> To: freebsd-questions@freebsd.org Subject: watchdog questions Message-ID: <4A00AA73.8080101@wcubed.net>
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I need some help understanding FreeBSD's kernel watchdog functionality. I've been reading up, and here's what I think I understand (correct me if I'm wrong): If a watchdog timer is set in the kernel and not reset or disabled within the time given, the kernel reboots the system. 'watchdog -t <n>' starts a watchdog for n seconds. Runing watchdog(8) again in <n seconds, resets the timer. If 'watchdog -t 0' is run, the kernel disables the watchdog. watchdogd(8) either runs stat(2) on /etc, or a user-defined cmd (with -e), and resets the watchdog only on a zero exit code. There's a few things that aren't clear, though: How many watchdog timers can be enabled at a given time? If more than one, does a single 'watchdog -t 0' disable all timers? Upon timer expiration, can the kernel be configured to do anything OTHER than rebooting? Is it the general idea that watchdog(8) would be run in a script, making sure the script doesn't hang? And that watchdogd(8) is run to ensure the entire system doesn't hang?
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