Script to auto restart a service in linux

You can create a script file that is called by cron at whatever interval you find appropriate.

You can decide to have it analyze any of the below for indicators if the service should be restarted.
* the output of a log file to make decisions
* verify open ports if it is a network service
* check the output of lsof or ps if it is a system service

However when a service goes down it may be due to some configuration issue which will not be resolved with a service restart, rather than having it continually attempt to restart a service it may be safer to have it alert you of the failure so you can address it and have confidence in continued operations.

There is a software called nagios (http://www.nagios.org/) that monitors if a service is available on a computer and raises an action if not. I never used it, but maybe it is what you are looking for.

You could easily just monitor a PID file for the service if that service creates one. If the PID file is not as expected, send a message to the admin and try to restart the service. Executing ps with a search using grep to find a running process would also work. As was mentioned earlier, monitoring the messages log would probably be the least effective way of doing this. Just about any modern monitoring software (like Nagios mentioned earlier) will do this for you with little effort needed.