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. It's current release, version 2.0, is stable and production ready. You can take a look at Nagios at http://www.nagios.com.
Development of Nagios has not stopped with version 2.0, though. Nagios' principal developer, Ethan Galstad, has recently released some information on the status and potential features of the next release, version 3.0. Galstad's announcement also suggests an alpha release of version 3.0 could be scheduled as early as the end of February 2007.
Features: What's new in Nagios 3.0
So what's new with version 3.0? Well, a lot. Let's walk through the major new features and look at how some of Nagios' old features have been expanded or changed.
One of the interesting features introduced in Nagios 2.0 was adaptive monitoring. Adaptive monitoring allowed a Nagios configuration to be changed during runtime. For example, you can change the command being used to check a host, based on changing conditions in your environment. In the new version, this functionality is expanded to include the ability to change the times during which checks are scheduled to occur. This allows you to turn on/off checks at specific times according to conditions in your environment.
Notifications have also been enhanced, now allowing a delay to be added to first notifications. Notifications can be generated when flapping is disabled and, most importantly, notifications can now be sent out when a scheduled downtime starts, ends or is cancelled.
Objects and templates haven't been forgotten either. One particularly useful change is the ability to use multiple templates for objects. Another is the addition of custom variables in host, service and contact objects. Version 2.0 only allows the application of one template to an object. Multiple templates offer greater flexibility and power, which will make a significant difference to the configuration of objects.
Custom variables allow you to define your own directives in object definitions and, therefore, attach additional information about an object to its definition. These variables can be retrieved and used elsewhere in your Nagios environment. For instance, you could define the SNMP community strings for a host in its definition and then use these later in a check or external command.
Other object and template changes include: merging service and host-extended information object data into service and host object definitions, and adding group member directives to the host and service group objects.
Enhancements to external commands are also present, including the ability to process commands found in an external file. The suggested use of this functionality is for passive checks with long output or complicated scripting. A further added to Nagios 3.0 is that external command checking is now turned on by default. In previous versions, such checking was set off by default.
Host and service logic alterations have also been made. Most notably, host checks now run asynchronously in parallel with each other. This should help balance overall check performance. Another enhancement is the ability to cache host and service check results and a function to enable the predictive checking of dependent hosts and services.
The ability to output multiple lines of data from host and service checks has also been added. Previously, Nagios 2.0 was limited to a single line of output from checks, thus reducing the utility of some checks. Now, multiple lines can be received and processed by Nagios and the size of plug-in output has been correspondingly increased to 2Kbs.
A number of performance optimizations have been included in Nagios 3.0, as well as enhancements to the Nagios Event Broker and the embedded Perl interpreter. Also worth mentioning are updates to macros and to status, comment and retention data.
To see a full list of the changes, or if you wish to try Nagios 3.0 before its alpha release, you can download a current CVS snapshot from http://www.nagios.org/development/cvs.php. The Changelog file contained in the snapshot provides a reasonably full list of the proposed changes.