Munin is a free and open-source computer system monitoring, network monitoring and infrastructure monitoring software application. It offers monitoring and alerting services for servers, switches, applications, services, etc. It alerts the users when things go wrong and alerts them a second time when the problem has been resolved. Munin is written in Perl and uses the RRDtool to create graphs, which are accessible over a web interface. Its emphasis is on plug and play capabilities. About 500 monitoring plugins are currently available. It is intended to make it easy to determine “what’s different today” when a performance problem happens and to provide visibility into capacity and utilization of resources.
Munin was started by Jimmy Olsen late 2003, based on RRD tool by Tobi Oetiker. Development has slowed down since 2005, but Munin is a stable tool and is still maintained. One of the two ravens who report the news of the world to the god Odin is called Munin, and the other is named Hugin. Munin is ‘memory’
Munin has a master/nodes architecture in which the master connects to all the nodes at regular intervals and asks them for data. It then stores the data in RRD files, and (if needed) updates the graphs. One of the main goals has been ease of creating new plugins (graphs).