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Date: Mon, 4 Jun 2007 16:15:40 -0700
From: Andrew Sharp <andy.sharp@onstor.com>
To: Tim Gardner <tim.gardner@onstor.com>
Subject: watchdog device
Message-ID: <20070604161540.711da0db@ripper.onstor.net>
Organization: Onstor
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Here is the kernel help text for the watchdog device.  You can
configure the software watchdog by adding support for SOFT_WATCHDOG.
CONFIG_WATCHDOG is already set to 'y'.  So, add a line
CONFIG_SOFT_WATCHDOG=y
after the CONFIG_WATCHDOG line in .config and do a 'make' in
linux-mips-2.6, or a 'make kernel-build' in the directory above
(cougar/linux/kernel).

The user process then has to open and write to the file descriptor at
least once a minute or the kernel will reboot.  I haven't tested it ~:^)


CONFIG_WATCHDOG=y

If you say Y here (and to one of the following options) and create a
character special file /dev/watchdog with major number 10 and minor
number 130 using mknod ("man mknod"), you will get a watchdog, i.e.:
subsequently opening the file and then failing to write to it for
longer than 1 minute will result in rebooting the machine. This
could be useful for a networked machine that needs to come back
on-line as fast as possible after a lock-up. There's both a watchdog
implementation entirely in software (which can sometimes fail to
reboot the machine) and a driver for hardware watchdog boards, which
are more robust and can also keep track of the temperature inside
your computer. For details, read <file:Documentation/watchdog/watchdog.txt>
in the kernel source.

The watchdog is usually used together with the watchdog daemon
which is available from
<ftp://ibiblio.org/pub/Linux/system/daemons/watchdog/>. This daemon can
also monitor NFS connections and can reboot the machine when the process
table is full.




CONFIG_SOFT_WATCHDOG=[y|m]

A software monitoring watchdog. This will fail to reboot your system
from some situations that the hardware watchdog will recover
from. Equally it's a lot cheaper to install.

To compile this driver as a module, choose M here: the
module will be called softdog.



CONFIG_WATCHDOG_NOWAYOUT=n

The default watchdog behaviour (which you get if you say N here) is
to stop the timer if the process managing it closes the file
/dev/watchdog. It's always remotely possible that this process might
get killed. If you say Y here, the watchdog cannot be stopped once
it has been started.
