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.

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

sudo apt-get install nmon

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

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.


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.


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

You wI’ll see the following output:


Use the d key to get information about disks.

You wI’ll see the following output:


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.


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.