Nagios Core is a powerful, enterprise-class host, service, application, and network monitoring program. It has been designed to be fast, flexible, and rock-solid stable. Nagios runs on *NIX hosts and can monitor Windows, Linux/Unix/BSD, Netware, and network devices.

Nagios Core serves as the basic event scheduler, event processor, and alert manager for various monitored elements. It features several APIs which are used to extend the program's initial capabilities in order to perform additional tasks. It is implemented as a daemon written in C for performance reasons. Nagios Core is designed to run natively on Linux/*nix systems.

Nagios Core has been designed with a focused, extensible architecture, which has been designed specifically to be flexible and scalable. It provides several APIs to allow its feature-set to be easily extended via additional add-ons.

Key Features Include:

• Complete infrastructure monitoring.
• Hundreds of free add-ons.
• Open source monitoring engine.
• Forum support.

Nagios Core is primarily focused on check scheduling, check execution, check processing, event handling, and alerting. Tasks such as performing checks, sending notifications, processing performance data, are usually considered out-of-scope for Nagios Core and are handled by other Nagios projects.

Nagios Core has a default CGI interface. These will provide you with the basic functionality that is required to view and manage the various elements monitored by Nagios Core. They have become the standard Nagios Core interface, and are often used as an API by many Nagios extensions. Nagios Core allows you to deploy additional front-ends to customize the look, feel and function of your UI.

Nagios Core has a rich variety of add-ons, which provide additional features that are out-of-scope for Nagios Core itself. These include configuration front-ends, performance graphing, auto-discovery, and distributed monitoring.