With personnel resources becoming more and more scarce, no IT department can
really afford to regularly check all systems manually. Networks that are growing
more and more complex especially demand the need to be informed early on of
disruptions that have occurred or of problems that are about to happen. Nagios,
the Open Source tool for system and network monitoring, helps the administrator
to detect problems before the phone rings off the hook.
The aim of the software is to inform administrators quickly about questionable
(WARNING) or critical conditions (CRITICAL). What is regarded as 'questionable' or
'critical' is defined by the administrator in the configuration. A Web page sum-
mary then informs the administrator of normally working systems and services,
which Nagios displays in green, of questionable conditions (yellow), and of criti-
cal situations (red). There is also the possibility of informing the administrators in
charge-depending on specific services or systems-selectively by e-mail but also
by paging services such as SMS.