[ Thanks to tvprboy for
this link. ]
“Nagios: This is one of the most popular web based Linux
monitoring systems nowadays, actually it?s industry standard for IT
infrastructure monitoring. Licensed under GPL Nagios is available
for everybody free of charge and allows to monitor availability and
response time of network services, usage of system resources like
CPU load, RAM allocation etc., number of logged in users and
many-many more. It doesn?t makes sense to list here everything that
can be monitored by Nagios but its nature implies that main Nagios
instance (server) collects information from either local system or
Nagios clients (agents). It means you can install client software
on number of Linux, BSD, Windows hosts or Cisco devices, point them
to Nagios server and see states of their services or processes in
one place: Nagios web based monitoring tool (see the screenshot
below).”