How to add Linux host to Nagios monitoring server using NRPE

In our earlier tutorials, we installed & configured Nagios Monitoring server & also added Windows host to Nagios Server using NSClient++. In this tutorial, we will learn how to add a Linux host to the Nagios monitoring server.

NRPE aka Nagios Remote Plugin Executor, allows us to monitor the local resources of a Linux host on the Nagios monitoring server. It needs to be installed on both the Linux host & on the Nagios server. So let's start with configuring the Linux host first.

(Recommended Read: Easy guide to setup Nagios monitoring using SSH (check_by_ssh))

Add Linux host to Nagios monitoring server

Configuring Linux Host

Before we begin installtion, we will first install the Nagios plugin on the host

• Installing required packages

Install the following packages to resolve all dependencies required for installing the plugins ,

• Download the Nagios Plugins

Next, we will download the Nagios plugins from the following url

• Installing & Configuring the plugin

Before installing the Nagios plugin, we need to add a user "nagios"

after creating a user, go to the folder with plugins. We will now extract the plugins

And now we will compile & install the plugins

•  Changing the ownership of plugin folder

After the plugins are installed, we will change the ownership of the plugins folders

• Downloading & installing NRPE

Now its time we download  the plugin, use the link below

then, extract the plugin

next, we compile & install it

• Making changes to Config file

Now open the config file and add the localhost and IP address of the Nagios Monitoring Server.

& in /etc/services file , add following line & save it

finally, start xinetd,

Note:- xinted is installed on most of the Linux distributions by default, but if that is not the case you install it using

yum install xinetd.

• Verifying connectivity from Nagios to host

Now that the plugin has been installed, we will verify connectivity of host from nagios server by following on Nagios server

where 192.168.1.115 is the IP address of the Linux host that is to be monitored.

Note:- NRPE config file (/usr/local/nagios/etc/nrpe.cfg) has some of the commands already written on it, you can modify them as per your needs & can test them by directly running these on the terminal.

Next, we move on to Nagios & configure it to receive updates from the Linux host.

Nagios Server configuration

• Download & install NRPE

First, we download & install remote plugin on Nagios server , as we did on Linux host

• Adding remote Linux host

Create two files named linux_hosts.cfg & linux_services.cfg in folder “/usr/local/nagios/etc/”

then we will edit nagios.cfg & add the following two files in it

Now, we will copy the default templates for hosts & services, present in /usr/local/nagios/etc/objects/ to these files & will edit them as per our need

Firstly , open  linux_hosts.cfg & edit it (see screenshot)

then we will add services in linux_services.cfg (see screenshot)

& lastly, we will add NRPE command definition to /usr/local/nagios/etc/objects/commands.cfg

& add the following command definition

• Verifying Nagios configuration file

If there are any errors, resolve them & then restart the nagios server for changes to take effect.

• Open web-console

Open your web-console, by typing your Nagios IP address or FQDN  in your browser & enter credentials for Nagios. Once inside the web-console, goto services page & you should see that services for your Linux hosts have added here for monitoring.

So, this was our tutorial on how to add Linux host to the Nagios monitoring server. If you have any queries or comments, please mention them in the comment box down below.