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nmon for Linux - nmon is short for Nigel's performance Monitor for Linux on POWER, x86, x86_64, Mainframe & now ARM (Raspberry Pi)

This systems administrator, tuner, benchmark tool gives you a huge amount of important performance information in one go. It can output the data in two ways

  1. On screen (console, telnet, VNC, putty or X Windows) using curses for low CPU impact which is updated once every two seconds. You hit single characters on you keyboard to enable/disable the various sorts of data.
    • You can display the CPU, memory, network, disks (mini graphs or numbers), file systems, NFS, top processes, resources (Linux version & processors) and on Power micro-partition information.
    • For lots of examples, see the "Screen shots" from the left menu.
    • As you can see on the left lmon12e now in colour
  2. Save the data to a comma separated file for analysis and longer term data capture.
    • Use this together with nmon Analyser Excel 2000 spreadsheet, which loads the nmon output file and automatically creates dozens of graphs ready for you to study or write performance reports.
    • Filter this data, add it to a rrd database (using an excellent freely available utility called rrdtool). This graphs the data to .gif or .png files plus generates the webpage .html file and you can then put the graphs directly on a website automatically on AIX with no need of a Windows based machine.
    • Directly put the data into a rrd database or other database for your own analysis


  • nmon is a single binary for
    • each operating system (Red Hat, SUSE, Ubuntu, Fedora, OpenSUSE etc.) and
    • each platform (Power, Mainframe, x86 or x86_64).
  • Installing is very easy - just start the right executable.
  • Why use five or six tools when one free tool can give you everything you need!!
  • For the pre-compiled versions - click on Download
  • For the source code & compiling - click on Compiling nmon

Data Analysis

Once you save the nmon data you have a number of options to analyser and graph the statistics.

  • nmon Analyser Excel Spread-sheet Download
    • This is the original tool and been developed over many years by Stephen Atkins
    • You can request support via the Performance Tools Forum
    • However, Linux users might not like the idea of using the Microsoft Excel Spreadsheet and automating the creation of graphs can be tricky.
    • Sample Graphs out of the many (see screen shots for more and larger examples:
    • CPU Compared to Disk I/O
    • Disk Read and Write with I/O per second
    • Hot Disk analysis with Average, Weighted Average and Peak values
    • Network Read (top half) and Write (bottom half) Transfer Rates
  • nmon Consolidator Excel Spread-sheet Download
    • This is a newer tool and can combine nmon output files. It is by Stephen Atkins
    • Again its Microsoft Excel Spreadsheet
  • nmon2rrd
    • Microsoft free tool
    • This tool uses the excellent rrdtool to generate all the graphs and a website .html file.
    • Download it from the nmon for AIX Wiki
    • This allows the automated analysis on many machines and viewing via a Browser.

Now - Open Source

nmon for Linux is a single source code file of 5000 lines and single makefile. This will enable you to compile nmon for your precise Linux version (if you can't find what you want in the binaries) and open a few other possibilities:

  • Fixing my code - be gentle, please.
  • Removing magic numbers i.e. constants that can catch us out as machines get larger
  • Developing for some strange environments like machines with no disks, blades that boot from NFS, internal Linux based engines within disks subsystems, embedded machines.
  • Who knows we may get nmon for Linux within the Linux Distro's - any one know how to go about that?

Thanks for your support, suggestions, testing and I hope this starts a whole new wave of development and interest.


  • nmon for Linux was an internal project at IBM for many years and was released to open source under GPL on 27th July 2009.
  • is being used to host the project, see
  • nmon for AIX does has a similar online look, file format but was always complete different source code. It is now integrated into AIX topas command from AIX 5.3 TL09 and AIX 6.1 TL02. nmon for AIX is not open source. For more information nmon for AIX Wiki

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Page last modified on June 02, 2012, at 02:35 PM