CentOS/RHEL Watchdog install 
Watchdog is a software which resets the machine if the machine is in some of the crash defunct state but the kernel lives somehow. The watchdog can be configured to check if the system is responsive via writting to the /dev/watchdog and some other subsequent check could be set up as well.

Watchdog opens /dev/watchdog and keeps writing to it often enough to keep the kernel from resetting, at least once per minute. Each write delays the reboot time another minute. After a minute of inactivity the watchdog hardware will cause the reset. In the case of the software watchdog the ability to reboot will depend on the state of the machines and interrupts.

# yum install watchdog

watchdog consists of the watchdog daemon and a kernel module softdog.

/lib/modules/2.6.18-238.9.1.el5/kernel/drivers/char/watchdog/softdog.ko

If the watchdog complains the device through which the process comunicates with the module /dev/watchdog is missing you have to create the device

# mknod /dev/watchdog c 10 130

in basic configuration the only change sufficient in /etc/watchdog.conf is to uncomment

file = /var/log/messages
watchdog-device = /dev/watchdog

I do recommend to check the watchdog documentation bundled in /usr/share/doc/watchdog

# rpm -ql watchdog
/etc/rc.d/init.d/watchdog
/etc/sysconfig/watchdog
/etc/watchdog.conf
/usr/sbin/watchdog
/usr/sbin/wd_keepalive
/usr/share/doc/watchdog-5.6
/usr/share/doc/watchdog-5.6/AUTHORS
/usr/share/doc/watchdog-5.6/COPYING
/usr/share/doc/watchdog-5.6/ChangeLog
/usr/share/doc/watchdog-5.6/IAFA-PACKAGE
/usr/share/doc/watchdog-5.6/NEWS
/usr/share/doc/watchdog-5.6/README
/usr/share/doc/watchdog-5.6/README.watchdog.ipmi
/usr/share/doc/watchdog-5.6/TODO
/usr/share/doc/watchdog-5.6/examples
/usr/share/doc/watchdog-5.6/examples/README
/usr/share/doc/watchdog-5.6/examples/another-chance.sh
/usr/share/doc/watchdog-5.6/examples/dbcheck.sh
/usr/share/doc/watchdog-5.6/examples/repair.sh
/usr/share/doc/watchdog-5.6/examples/systemcheck.sh
/usr/share/doc/watchdog-5.6/examples/uptime.sh
/usr/share/man/man5/watchdog.conf.5.gz
/usr/share/man/man8/watchdog.8.gz
/usr/share/man/man8/wd_keepalive.8.gz


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