Check_MK is an extension to the Nagios monitoring system that allows creating rule-based configuration using Python and offloading work from the Nagios core to make it scale better, allowing more systems to be monitored from a single Nagios server.It comes with a set of system checks, a mod_python and JavaScript based web user interface, and a module that allows fast access to the Nagios core. On top of Nagios it also adds additional features.