[ Thanks to Jane Walker for this link.
]
“Nagios is a free, open source enterprise monitoring tool
designed to run on Linux. It has extensive monitoring and
management capabilities that allow you to check applications,
databases and network devices, as well as Windows and Unix/Linux
hosts and services. It is easy to install, fast to configure and
highly customizable.“Nagios also comes with a Web-based console, extensible Nagios
Event Broker (NEB), that allows you to integrate Nagios with other
tools, like database back-ends, and a large collection of
monitoring commands and capabilities…”