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OpenBSD General Other questions regarding OpenBSD which do not fit in any of the categories below. |
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watchdog
Hallo, I have an OpenBSD4.8 installed on a Intel Atom D410 motherboard, I want to enable watchdog, the mobo should have hardware timer, but I cannot enable it in the bios. For linux there is a software watchdog, but is for linux only, is there something similar for openbsd?
Thanks, Elerdin. |
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OpenBSD's watchdog(4) uses the first available hardware watchdog timer. This is a hardware-only implementation, since at timeout, the BIOS reboots the platform. As I understand it, a "software watchdog timer" would require a running system, precluding a forced reboot in the event of a system crash.
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Yes, I had the same idea, but I hoped I was wrong ;-) So I tried another way, I put to 0 the ddb.panic in sysconf, if I understood right this will force a reboot in case of kernel panic, is this right?
Thanks, Elerdin. |
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Right. In the event of a managed kernel panic, the kernel will attempt to dump RAM contents into swap space, and then reboot the system. This will work, if the kernel is still functioning.
The advantage of using a hardware watchdog timer -- if the hardware has one -- is that it acts as a dead man's switch so that hardware gets rebooted automatically if the kernel isn't communicating with the hardware regularly. |
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Well, next time I'll search a cheap motherboard that support watchdog timer (any suggestion is appeciated ;-))
Thanks, Elerdin. |
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This is most advantageous for remote servers, and one series of Dell server platforms with watchdog timers got a mention in 2005 in the OpenBSD Journal.
OpenBSD/i386 has some hardware listed as officially supported:There's no list for amd64 or sparc64. |
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I'd say almost every system has a watchdog timer available, unfortunately drivers have to be written to take advantage of them.. usually it's a chipset feature (..southbridge), supported by the chipset driver.
However, there do exist some PCI cards.. berkwdt(4) was added a few releases ago, it's for Berkshire products. A few of my systems have an it(4) device, this is a temperature sensor.. but it also includes a watchdog timer that the kernel can use. One problem is that if the interval is too short, the system might reboot.. even if the kernel may have recovered within a few seconds, also, the filesystem is left in an inconsistent state and you can lose data. |
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