Once Nagios is installed, it will automatically configure a few basic monitors directed toward its own server. If we click on the Hosts link in the web administration site, we are presented with this:
The local server is all that we are currently watching. This is useful to verify that Nagios is working as intended, but we need to monitor one or more database servers as well. In this recipe, we will learn how to watch external servers. By the end, we should see at least one more server listed by Nagios.