Where can I download Nagios?
The Nagios server software is available for most major distributions of Linux using the standard package management tools. Your distribution will have documentation available on how to install Nagios. This is usually the quickest and simplest way to get up and running. You will need the core Nagios server package, and at least one of the NRPE or NSCA add-ons. NSCA is required to utilize the alerting features of the Opengear distributed hosts, installing both NRPE and NSCA is recommended. You will also require a web server such as Apache to display the Nagios web UI (and this may be installed automatically as a dependency of the Nagios packages). Alternatively, you may wish to download the Nagios source code directly from the Nagios website nagios.org and build and install the software from scratch. The Nagios website (http://www.nagios.org) has several Quick Start Guides that walk through this process. The Nagios server can also be installed as an application or as a virtual appliance