Install and Use nmon Tool To Monitor Linux Systems Performance

Posted on in Categories last updated October 3, 2012

How do I install nmon command under Linux operating systems to find out performance information for my CPU, memory, network, disk, virtual memory, top process and other part of my HP server running on Debian Linux or CentOS Linux 6.x amd64 bit server?

This systems administrator, tuner, benchmark tool gives you a huge amount of important performance information in one go with a single binary.

It works on Linux, IBM AIX Unix, Power, x86, amd64 and ARM based system such as Raspberry Pi. The nmon command displays and records local system information. The command can run either in interactive or recording mode.

Debian / Ubuntu Linux Install nmon

Type the following apt-get command:
# apt-get install nmon
Sample outputs:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 52.5 kB of archives.
After this operation, 164 kB of additional disk space will be used.
Get:1 squeeze/main nmon amd64 13g+debian-1 [52.5 kB]
Fetched 52.5 kB in 1s (32.0 kB/s)
Selecting previously deselected package nmon.
(Reading database ... 29511 files and directories currently installed.)
Unpacking nmon (from .../nmon_13g+debian-1_amd64.deb) ...
Processing triggers for man-db ...
Setting up nmon (13g+debian-1) ...

A note about RHEL / CentOS Linux user

You can download nmon binary version by visiting this page.

Compiling Nmon Under RHEL / CentOS / Fedora / Scientific Linux

Grab the source code and makefile using wget command:
$ wget
$ wget

You need to install ncurses-devel package, enter:
# yum install ncurses-devel
Rename file, enter:
$ mv lmon14g.c lmon.c
Open the makefile and find the the directive that matches your platform and Linux release:
$ vi makefile
To compile for RHEL/CentOS v5.x, enter:
$ make nmon_x86_rhel52
Sample outputs:

cc -o nmon_x86_rhel52 lmon.c -g -O2 -D JFS -D GETUSER -Wall -D LARGEMEM -lncurses -g

You can move nmon_x86_rhel52 to /usr/local/sbin, enter:
# mv nmon_x86_rhel52 /usr/local/sbin/nmon

How do I use nmon?

Simply type the following command:
# nmon
Sample outputs:

Command to analyze Linux server performance - cpu / memory / network / disk and much more
Fig.01: nmon startup screen

nmon keyboard shortcuts

  • q – To stop and exit nmon.
  • h – To see quick help (hint) screen and press h again to remove the hints.
  • Use the following command to turn on or off stats:
    • c – See cpu stats.
    • m – See memory stats.
    • d – See disk stats.
    • k – See kernel stats.
    • n – See network stats.
    • N – See NFS stats.
    • j – See file system stats.
    • t – See top process.
    • V – See virtual memory stats.
    • . – See only busy disks/procs.
    • v – Verbose mode (display as Ok/warning/danger on screen).

Sample output from my home server:

nmon Command Examples
Fig.02: nmon command in action

How do I set default monitoring options for nmon?

To see the memory, network, disk and processor statistics immediately after the nmon command is started, run (or add in your shell startup file):
# export NMON=mndc
Run the nmon command:
# nmon

Capturing and analyzing data with nmon

You can capture the data to a file for later analysis and graphing. Type the following command:
# nmon -f -s2 -c 30
# nmon -ft -s 30 -c 120
nmon will run as a daemon in the background and you can log out. nmon will complete the data file capture and it will save in a file *.nmon file such as nas02_120806_0202.nmon. Where,

  1. -f : Start data collect mode and output in spreadsheet format.
  2. -s 2 : Wait between 2 seconds refreshing the screen.
  3. -c30 : Total number of refreshes (30).
  4. -t : Spreadsheet includes top processes.
  5. -d disks : to increase the number of disks [default 256]
  6. -x : Capacity planning (15 min for 1 day = -fdt -s 900 -c 96)

You need to download nmonanalyser which is an Excel spreadsheet that takes an output file from nmon and produces some nice graphs to aid in analysis and report writing.

Check out related media

See a quick installation and demo of nmon command:

(Video 01: nmon Linux installation and quick usage demo)

Recommended readings:

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

24 comment

    1. Htop is nice, but it’s not nearly as informative. For example, you can not see network traffic at all. And even some of the areas that Htop provides information on, it’s not nearly as in depth as nmon.

  1. Hi I used nmon precompiled binary file to monitor my server (centos 6.4).Its recorded 230 kb and 630 kb data for 10 minutes.I used java nmon analyzer to see the graphs but it closed suddenly when I tried to open the file.I dont know why is it happened.I installed java and set environment variables successfully but this software didnt worked for me.Any help?Its very urgent for me.

  2. Hi,

    I have developped a complete Application over Splunk which uses Nmon and provides an Entreprise class solution to exploit Nmon performance monitors for large and historical vision:

    The Application is open source, Splunk itself can be used for free with Up to 500mb of volume indexing per day.

    The solution provides many interfaces to Analyse Nmon data and is compatible with AIX, Linux and Solaris.

  3. Is there a document that defines the structure of the CSV file? i.e. for each record type, what data appears in each field.

    I have been searching for a week and canot find anything,and i do not fancy revverse engineeering the C code of nmon or the VB of the Excel nmon analyzer

  4. trying to install Nmon for linux with command rpm_nmon, got this message:
    error: failed dependencies: () (64bit) is needed for nmon-15g-4.2.x86_64
    Where can i get such dependency ?


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