We’ve all had the dreaded phone call “did you know XYZ server is down”? This is normally followed by a flood of calls and at some point questions regarding how to be more proactive in responding to issues. First and foremost, let me be clear no matter how good of an IT admin you are, there will always be some unexpected downtime (unless you work for the only SMB size company on the planet with clustered and redundant everything). That said careful planning and monitoring can help reduce downtime and help to provide a more proactive response to outages. There are untold amounts of monitoring solutions out there from Opsview, PRTG, Nagios XI, Solar Winds, etc. Each of these products is certainly a fine solution for monitoring, however monitoring gets expensive quickly. Perhaps you need to build a proof of concept or just need something simple and free. Enter Part 1 of Monitoring Your Servers For Free!
For alert monitoring with granular features such as monitoring specific services on your server infrastructure or simply running ping checks to make sure you wireless APs are alive and responsive, Nagios core is hard to beat. If you’re a Linux admin this should be a walk in the park for you, however even for a Windows admin this is a fairly easy setup with solid instructions and a few gotchas. The link below details the installation steps for both Debian and RHEL flavors of Linux, however some undocumented gotchas to be aware of (if you want to access the web page from something other than the local host you will need to create iptables firewall exceptions (as well as firewalld for RHEL 7). Below is an example of an iptables entry to allow inbound traffic on port 80, the same can be applied to 443 and any other needed ports.
iptables -A INPUT -p tcp -m tcp –dport 80 -j ACCEPT
Installation Instructions: http://assets.nagios.com/downloads/nagioscore/docs/Installing_Nagios_Core_From_Source.pdf
Now that we’ve got a Nagios server up and running, we’ll start monitoring services on our infrastructure. Stick around for part 2 coming next week as we dive into service monitoring.