Monitoring with Nmon


I’m a big proponent of command-line tools to help debug misbehaving nodes, because many times I only have command-line access to the node. In the previous two articles, I covered two classes of tools I use: top-like tools and stat-like tools. In my experience, the most common user issue is performance – Why isn’t my application running? Why isn’t my application running fast? Why isn’t my application running as fast as it did yesterday? Therefore, I need tools to help me examine node performance, so I need a combination of top- and stat-like tools, which is why I like using nmon.

Nmon can be used as a top-like tool to watch what is happening on the system, but you can also use it to capture system information that can be used to understand what the system is doing. The many nmon options monitor what is happening on the system, and some even produce ASCII charts. It’s a great way to get a quick visual impression of what is happening in the system.

Nmon can also capture a great deal of information from the system and produce CSV files for postprocessing. However, the results are typically not easy to postprocess, so you need to use one of the tools mentioned in this article to visualize the data.

Give nmon a chance. I think you will like what it can do for you.