Nmon Monitoring Tool

Monitoring Linux with nmon

nmon for Linux

nmon is a system monitoring tool which allows you to monitor the most important aspects of your Linux server. Using nmon, you can monitor CPU, memory, network, disk, filesystems, NFS and Top Processes.

nmon is open source and free. It can be downloaded from a number of sites in either a pre-compiled version for popular Linux distributions. Or you can download the source code and compile this yourself.

Output from nmon can be saved and analysed using various software such as the "nmon Analyser Excell 2000" program. Here you can create some great looking graphs displaying all aspects of your server.

Installing nmon

nmon can be downloaded from the following locations if it is not already present in your Linux systems repositories.

rpm based packages are available from: nmon rpm package download

Simply download and install the right release for your server.

Example : RHEL-CentOS rpm download and install

cd /usr/src
wget http://packages.sw.be/nmon/nmon-14g-1.el6.rf.x86_64.rpm
rpm -ivh nmon-14g-1.el6.rf.x86_64.rpm

Example : Ubuntu apt install

sudo apt-get install nmon

For other Linux distributions you can download pre-compiled binaries from:

nmon source : http://nmon.sourceforge.net/pmwiki.php?n=Site.Download

Once you have successfully installed nmon, you can start the program by simply typing nmon at the terminal

A screen similar to the one below should now be showing:


h = Help Information
t = Top Process Stats
c = CPU by Processor
l = Longer term CPU Averages
m = Memory and Swap Stats
j = JFS Usage Stats
h = Help Information
n = Network Stats
d = Disk I/O Stats
o = Disk %Busy Map
k = Kernel Stats and Loadavg
v = Virtual Memory
g = User defined disk groups
v = Verbose Simple Checks
b = Black and White Mode
h = Help Information

Set Default Monitoring Options for nmon

Normally when you start nmon, you will see the above screen at startup, however, it is possible to customise this by adding a simple variable to your shell startup script:

#Set basic nmon startup screen
export NMON=mndc

Alternatively, before you type "nmon" to start issue the "export NMON=mndc" command.

In the above example, the "m" is for Memory and Swap stats, "n" is for Network stats, "d" is for disk stats and "c" is for CPU stats.

nmon Basics Video

Below is a video overview of some of the basic functionality that con be found within the nmon monitoring tool.