sysadmin
Nagios 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. 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.