Review: Nagios
I don’t think I’ve mentioned this before.
Some time ago, I was having problems with traffic on my network. Something, somewhere was apparently causing some issues with bandwidth on our Internet connection. Or, at least, that’s what our ISP kept telling us. It was, I think, the excuse they were using to avoid dealing with an e-mail problem.
Regardless, I had to find a tool to monitor our network traffic. I ended up using Wireshark for that, but along the way, I discovered a number of OpenSource monitoring tools for various purposes. The one that impressed me the most was Nagios.
Nagios is, according to the opening paragraph on their website, “an Open Source host, service and network monitoring program.” While I never did configure anything to monitor the network, per se, I did configure this to watch both local servers and third-party web and mail servers.
First of all, it’s important to know that Nagios runs on Linux. So, to install the software, you first have to have an available Linux server on which to install it. I’m using an old workstation that I installed the latest version of Fedora, the free version of RedHat. Getting the initial install done wasn’t very hard at all. In fact, there were RPMs available, so all I had to do was use RedHat’s package manager to get the base install loaded on the machine.
After the initial software load, I mainly followed the Quick Install instructions that they link to on the first page. Then, since I was mainly monitoring Windows servers and workstations, I found the cleverly titled help page, “Monitoring Windows Machines“, and followed that. This page ran me through the basics of installing the NSClient++ on a Windows machine and configuring Nagios to connect to and monitor that client. One thing that I had to find out the hard way was that the entries for the monitored systems have to be duplicated for each host. In other words, there is no way to just list all the Windows systems you want to monitor. You have to created entries describing each host individually. That’s not a big deal, honestly, since you can open the configuration files in a text editor and just copy, paste and edit the required entries.
I did have a few false starts here, until I figured out the correct syntax and the fact that every host has to be part of a previously defined group. But, other than that little glitch, configuration was fairly simple.
It took a little more digging, but I later found instructions for passively monitoring services running on servers without a client. I now use my private installation of Nagios to monitor our company webserver, both POP3 and SMTP on our hosted e-mail server, as well as my two Windows 2003 servers. I can even check on the Microsoft SQL database, thanks to information I got from this post on the OSdir mailarchive. And, did I mention that all this software was free? Yeah, the documentation wasn’t the best and it took me a little while to figure out the install and config, but it was far easier than the other monitoring software I played with and I can let anyone who has the username and password check these stats from their own workstation via a web browser. How cool is that? Oh, and did I mention that this can be used to monitor Linux/Unix systems, Windows systems and even Netware systems? Nagios pretty well covers it all!
(Oh, and as a side note, if you’re messing around with the configuration and want to reset the statistics, just stop the service and delete /usr/local/nagios/var/status.dat, then restart the service. All your counts will zero and all the checks will start fresh.)
In short, if you’re looking for a low-cost but versatile monitoring system and aren’t afraid to read the documentation, I highly recommend investigating Nagios.
