Chapter 4. Configuring Nagios

After installation, you need to configure Nagios before it can start. Nagios is configured by way of text files that contain directives and definitions. It can be a beast to configure for the first time because the definitions are self-referential and there’s a lot to define.

To get started, Nagios needs to call plugins during a time period against hosts and services and send notifications to contacts if a check returns a bad status, so you need to define the checks, time periods, hosts, services, notification commands, and contacts (and that’s all mandatory). Because so many objects refer to so many other objects, it can be hard to know where to begin to explain it all. Don’t be discouraged; Nagios comes with options to generate sample configuration files, and further, there are a few shortcuts you can take to bootstrap the configuration process (see Chapter 5, “Bootstrap the Configs”), but first you need a good understanding of what a configuration looks like.