Munin is a tool to monitor your computers services and hardware. It shows per graphs over time, what your servers, desktops, routers, NAS-Appliances, USPs and other devices have to do. Peaks in load, weak spots for your network performance or memory holes show up easy by looking at the curves. The software is also easy to install. Due to automatically configurated plugins it presents a great number of graphs from the very start. So you will instantly get insights into the machines inner life.

You may add more or remove existing plugins to adapt the monitoring as required in your case. Further -- thanks to Munins simple API -- the writing of your own plugins is not a big thing. With them you may also monitor measured values, that have nothing to do with network or computers. Wether you count the number of persons or measure the temperature inside a building or want to observe the Google-Pagerank of your homepage -- as long as the info can be represented by a numerical value and you can process it in a script, your creativity knows no limit.

I use Munin -- with plugins of my own writing -- since 2005 to monitor my systems and services. Together with Michael Renner, who works for a Online-Bank administering their HA-Clusters, I wrote a reference book about Munin wich was published by OpenSourcePress in Munich in 2008. It tells you how to install and configure your Munin-Master and Munin-Nodes. Also contained is a catalog with short portraits of the standard plugins and hints on how to interprete them. Last not least it demonstrates and explains how to write your own plugins step-by-step along concrete examples.