Nagios

Nagios () is an open-source network and infrastructure monitoring system. It monitors hosts, services, and network devices, sending alerts when components fail and again when they recover. Originally written by Ethan Galstad in 1999 as NetSaint, it was renamed Nagios in 2002 after a trademark dispute. The name is a recursive acronym: "Nagios Ain't Gonna Insist On Sainthood."

Icinga is an open-source network monitoring system created in 2009 as a fork of Nagios. The project was started by a group of Nagios community developers who cited slow development, limited community input, and insufficient handling of contributed patches as reasons for the fork. The name is a Zulu word meaning "it looks for" or "it examines."

Checkmk is an open source IT infrastructure monitoring software system developed in Python and C++. It originated as an extension to Nagios and has since evolved into a self-contained monitoring platform.

computer system and network monitoring application software