Icinga is an extensible monitoring system . Icinga checks the availability of your infrastructure resources with notifications for outages. It was originally created as a fork of Nagios, adding a GUI, additional database connectors and a REST API to allow integration of extensions without complication modification of the application core. With Icinga you can monitor network services such as SMTP, POP3, HTTP and others, along with host resources including CUP load, disk usage and server components (from switches, routers and temperature, to humidity sensors). It uses a rule-driven configuration format that is user-friendly and keeps configuration work to a minimum by defining templates to apply to configuration objects. Icinga offers three distinct command types, check, notification and event commands. Each can be given default values, custom attributes, runtime macros and conditional behaviors. The simple plug-in system allows you to easily develop service checks, with optional interfaces, reporting modules and template based reports.