In this recipe, you'll learn how to use the debugging log file in Nagios Core to get various kinds of process information from the running program, considerably more than available in the standard
log_file. This is useful not just for debugging purposes when Nagios Core is doing something unexpected at runtime, but it is also useful to get a better idea of how the server is working in general and with your particular configuration.
You will need a Nagios Core server with version 4.0 or greater. You will need access to change the
nagios.cfg file and to restart the server.
In this example, we'll simply log everything we possibly can and then explain how to refine the logging behavior if necessary in the How it works section.