What Is Nagios?

Overview 
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.  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. 

Features 
Nagios has a lot of features, making it a very powerful monitoring tool.  Some of the major features are listed below: 

* Monitoring of network services (SMTP, POP3, HTTP, NNTP, PING, etc.) 
* Monitoring of host resources (processor load, disk and memory usage, running processes,
  log files, etc.) 
* Monitoring of environmental factors such as temperature  
* Simple plugin design that allows users to easily develop their own host and service checks 
* Ability to define network host hierarchy, allowing detection of and distinction between
  hosts that are down and those that are unreachable 
* Contact notifications when service or host problems occur and get resolved (via email,
  pager, or other user-defined method) 
* Optional escalation of host and service notifications to different contact groups 
* Ability to define event handlers to be run during service or host events for proactive problem resolution 
* Support for implementing redundant and distributed monitoring servers 
* External command interface that allows on-the-fly modifications to be made to the
  monitoring and notification behavior through the use of event handlers, the web interface,
  and third-party applications 
* Retention of host and service status across program restarts 
* Scheduled downtime for supressing host and service notifications during periods of planned outages 
* Ability to acknowlege problems via the web interface 
* Web interface for viewing current network status, notification and problem history, log file, etc. 
* Simple authorization scheme that allows you restrict what users can see and do from the web interface 

License 
Nagios is licensed under the terms of the GNU General Public License Version 2 as published
by the Free Software Foundation.  This gives you legal permission to copy, distribute and/or
modify Nagios under certain conditions.  Read the 'LICENSE' file in the Nagios distribution
or read the online version of the license for more details.  Nagios is provided AS IS with NO
WARRANTY OF ANY KIND, INCLUDING THE WARRANTY OF DESIGN, MERCHANTABILITY, AND FITNESS FOR A
PARTICULAR PURPOSE. 

The Nagios homepage is located at:

	http://www.nagios.org/

Cryptographic signatures and checksums may be provided by 
the developers at the URL(s) above.  Wiretapped recommends
that users check these before use of the software/information.