Install and Use nmon Tool To Monitor Linux Systems Performance

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.

Tutorial details
Difficulty Intermediate (rss)
Root privileges Yes
Requirements None
Time N/A
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:

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:

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:
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24 comments… add one
  • Deepak Jun 6, 2016 @ 9:51

    Very Useful .. Thanks a lot.

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