The Nagios web interface is part of the main Nagios sources and binary distributions. Therefore, if you installed Nagios, you also have the web interface files. The only thing you need now is a web server — in our case, it will be Apache 2 (visit http://httpd.apache.org/).

The web interface uses CGI mechanisms to work, as this is the most-commonly offered way to run applications. It also allows a more flexible set-up in terms of security as CGI binaries can be run as a different user than the one the web server is running as. It also uses additional files such as many static HTML pages, CSS, and images.

As described in the previous chapter, Nagios CGI scripts need to be able to write to the Nagios external command pipe. If you have followed the installation instructions provided in Chapter 2, Installation and Configuration, your Apache server already has the correct access rights. If you set up Nagios on your own, you need to make sure your web server can write...