System Administration

Essential System Tools: nmon – Curses based Performance Monitor

Last Updated on November 25, 2022

This is the latest in our series of articles highlighting essential system tools. These are small, indispensable utilities, useful for system administrators as well as regular users of Linux based systems. The series examines both graphical and text based open source utilities. For this article, we’ll look at nmon, a free and open source performance monitor. For details of all tools in this series, please check the table at the summary page of this article.

Nmon is short for “Nigel’s Monitor”. It’s a systems administrator, tuner, and benchmark all wrapped up in an easy-to-use tool. The utility displays performance information on the CPU, memory, network, disks (mini graphs or numbers), filesystems, NFS, top processes, resources (Linux version & processors) and more.

The software aims to be as frugal as possible, as it’s self-defeating for a performance monitor to consume large chunks of CPU cycles and memory.


Nmon is released under an open source license. It’s a single file written in the C programming language. Version 16h runs to 8,606 lines of code. If you want to compile that code, the developer also provides a Makefile to help, but you can also write your own. A Makefile defines set of tasks to be executed.

Alternatively, popular distributions provide a convenient package to download and install the software.

And the developer provides binaries for various Linux distributions including RedHat, SuSE, Ubuntu, Fedora, and OpenSUSE. And there’s support for other platforms besides x86 and x86_64, including POWER and ARM (for Raspberry Pi).

Next page: Page 2 – In Operation

Pages in this article:
Page 1 – Introduction / Installation
Page 2 – In Operation
Page 3 – CPU Stats
Page 4 – Memory Stats
Page 5 – Disk Stats
Page 6 – Kernel Internal Stats
Page 7 – Virtual Memory Stats
Page 8 – Network Stats
Page 9 – Top-processes
Page 10 – Resources
Page 11 – Summary

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Mark Regan
Mark Regan
4 years ago

What terminal/window settings do I use in PuTTY when running nmon to get the correct line drawing?