Review : Nagios Network Monitor
Published 27 Jun 2001 ~ revised 11 Nov 2004
As a technical consultant, my role within a project changes with each passing client. For the most part, however, I have primarily been involved with systems/web architecture and administration. To assist in these technical endeavors, I was directed to a simple tool called NetSaint . It's functionality can best be described in a blurb from the website:
"NetSaint is a program that will monitor hosts and services on your network. It has the ability to email or page you when a problem arises and when it gets resolved. NetSaint is written in C and is designed to run under Linux, although it should work under most other *NIX variants. It can run either as a normal process or as a daemon, intermittently running checks on various services that you specify. The actual service checks are performed by external "plugins" which return service information to NetSaint. Several CGI programs are included with NetSaint in order to allow you to view the current service status, history, etc. via a web browser."
Anyway, this tool is everything it says it is and more. I dropped NetSaint on a RedHat 7.1 box with a 6-gig hard drive and 48 megs of RAM. It's running over Apache 1.3.19 as a daemon, and doesn't appear to require too much of the system resources. In general, the administrator tweaks a massive configuration file containing the servers to be monitored, the manner of monitoring, the time interval to perform the checks, and the notification scheme (containing email addresses, pager numbers, etc). Then if a ping test times out, for example, NetSaint checks which contact should be notified (based on the time frames associated with each contact) and sends out an appropriate message indicating what's wrong. Solid!
The standard installation includes a suitable array of plugins for basic server monitoring: ping, http, telnet, tcp/ip port check, POP, dns, ssh, disk, process, and a bunch of others. The cool thing is, you can write your own plugins or download "extras" from the web, thereby enhancing the capabilities of NetSaint.
So, if you're looking for a great network monitoring tool, this is the one. The initial configuration can be a bit daunting, but it's well worth the peace of mind to know when a server goes down, you'll be paged within a minute or two.
Update, 22 Feb 2002: Because of some legal issues with the name "NetSaint," this software package is now called "Nagios." Further development under the old name has ceased (v0.0.7b8), and all future development will be through SourceForge.net. I have recently upgraded one NetSaint box to Nagios (v1.0a4), and did a clean Nagios install (same version) on another box. Both machines were NetBSD, 1.5 and 1.5.2 respectively. I didn't encounter any significant issues, and for the most part, the software hasn't changed very much. The only noteable update is the difference from old-style "host" configuration files, and the newer "template" style. Nagios will support old NetSaint host.cfg files (as I have opted to do), but will now support a cleaner host file architecture. As of yet, the packaged software does not contain sample host files for the template architecture - you must write it yourself (which is why I decided to stick with the old host.cfg file).
Update, 28 May 2002: If I was careful, I would have noticed that the Nagios distribution comes with a fun little binary called "convertcfg" that, surprise, converts your old host files to new template configuration files. It's located in the "contrib/" directory. The conversion process looks clean, but since I originally compiled Nagios to use host files, I would have to recompile the entire distribution just to use this supported functionality. No thanks. I'll do it some other day.
Update, 23 Jul 2004: I'm still using Nagios, and have really opened up more of the advanced features. I've since started using the template-based configuration files, and have found many of the user-contributed enhancements and tools to be useful and worthwhile. If you're using Nagios, be sure you've implemented host and service dependencies - my normal flood of alert emails has finally dwindled down to a manageable handful!
For more information and product specifications, check out the product page at Nagios.org.
Overall rating : A- (a sys admin's best friend, with hella configuration)
