freebsd at wcubed.net
Tue May 5 21:07:15 UTC 2009
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
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
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?
More information about the freebsd-questions