Nagios
In this section, we will explore the Nagios monitoring solution for overall server health.
Nagios has been around since 1999 and has a large community that provides plugins and extensions for various needs. There are extensive resources available for Nagios on the web, and commercial support if your organization requires it.
Since it has been around so long and many organizations use it, Nagios is the standard in network monitoring against which other solutions compare themselves. As such, it is the natural starting point for our journey through the monitoring landscape.
The name Nagios is a recursive acronym, which is a tradition in hacker circles. It stands for "Nagios Ain't Gonna Insist On Sainthood". Originally, the product was called NetSaint, but the name was rejected in favor of the Nagios acronym during a trademark dispute. The word agios also means angel in Greek, so it is a pretty clever acronym overall.
Here are some screenshots from a small demo Nagios installation...