Monitor Linux System Performance Using Nmon

Monitor Linux System Performance Using Nmon

Nmon (also known as Nigel’s Monitor) is a computer performance system monitor tool for the AIX and Linux operating systems developed by IBM employee Nigel Griffiths. The tool displays onscreen or saves to a data file the operating system statistics to aid in the understanding of computer resource use, tuning options and bottlenecks. This system benchmark tool gives you a huge amount of important performance information in one go with a single command. You can easily monitor your system’s CPU, memory, network, disks, file systems, NFS, top processes, resources and power micro-partition information using Nmon.

Installing Nmon

By default nmon is available in the Ubuntu repository. You can easily install nmon by running the following command:

sudo apt-get install nmon

How to Use Nmon to Monitor Linux Performance

Once the installation has been finished, you can launch it by typing the nmon command in the terminal.


You wI’ll see the following output:


You can see from the above screenshot that the nmon command-line utility runs completely in interactive mode, and you can easily toggle statistics using shortcut keys.

You can use the following nmon keyboard shortcuts to display different system stats:

q : to stop and exit Nmon
h : to see help screen
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
v : verbose mode

Check CPU by Processor

If you would like to collect some statistics on CPU performance, you should hit the c key on the keyboard.

After hitting the c key you wI’ll see the following output.


Check Top Process Statistics

To get stats on top processes that are running on your system, press the t key on your keyboard.

You will see the following output.


Check Network Statistics

To get the network stats of your Linux system, just press the n key on your keyboard.

You wI’ll see the following output:


Disk I/O Graphs

Use the d key to get information about disks.

You wI’ll see the following output:


Check Kernel Information

A most important key to use with this tool is k; it is used to display some brief information on the kernel of your system.

You will see the following output after hitting the k key on your keyboard.


Get System Information

A very useful key for every system admin is the r key which is used to give information on different resources such as machine architecture, operating system version, Linux version and CPU.

You will see the following output by hitting the r key.



There are many other tools that can do the same job of the Nmon, but Nmon is so usee friendly for a Linux beginner. Please feel free to comment if you have any questions.

Hitesh Jethva
Hitesh Jethva

Over 5 years of experience as IT system administrator for IT company in India. My skills include a deep knowledge of Rehat/Centos, Ubuntu nginx and Apache, Mysql, Subversion, Linux, Ubuntu, web hosting, web server, squied proxy, NFS, FTP, DNS, Samba, ldap, Openvpn, Haproxy, Amazon web services, WHMCS, Openstack Cloud, Postfix Mail Server, Security etc.

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