Munin is a tool for graphing all sorts of information about one or
more servers and displaying it in a web interface.  It uses the
execellent RRDTool (written by Tobi Oetiker) and is written in Perl.
Munin has a master/node architecture.  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 own "plugins" (graphs).

Homepage:
https://munin-monitoring.org/
