Description:

Nagios(R) is a host and service monitor designed to inform you of network
problems before your clients, end-users or managers do. It has been
designed to run under the Linux operating system, but works fine under
most *NIX variants as well. The monitoring daemon runs intermittent
checks on hosts and services you specify using external "plugins" which
return status information to Nagios(R). When problems are encountered, the
daemon can send notifications out to administrative contacts in a variety
of different ways (email, instant message, SMS, etc.). Current status
information, historical logs, and reports can all be accessed via a web
browser.