How to add a remote host to Nagios monitoring server

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This is a continuation of our previous post where we showed you how to install Nagios Server on Ubuntu 20.04. In this post, we focus on how you can add a remote host to the Nagios server. Without much further ado, let’s get on with it.

For demonstration purposes we will deploy a Ubuntu 20.04 host which will be our target system for monitoring.

Step 1: Install Nagios agent and plugins

First, update the package index as follows:

$ sudo apt update

Then install Nagiois NRPE and plugins as shown

$ sudo apt install nagios-nrpe-server nagios-plugins

Great, once installed, proceed to the next step.

Step 2: Configure NRPE agent

Once all the requisite packages have been installed, we need to modify the Nagios NRPE configuration file which is the /etc/nagios/nrpe.cfg file.

Open the file and locate the allowed_hosts attribute. By default, this reads as follows.,

Replace the second IP address with the private IP of the Nagios monitoring server. For example., nagios-server-ip

Also, locate the server_address attribute and set it to the remote Linux host that is to be monitored.


Save and be sure to restart the NRPE agent service for the changes to take effect.

$ sudo systemctl restart nagios-nrpe-server

To make sure the NRPE agent is running, verify using the command:

$ sudo systemctl status nagios-nrpe-server

Ensure that the service is running.

Step 3. Add a remote host to Nagios

The last step is to add the remote host to Nagios. So log in to the Nagios server and create a folder where you are going to place the configuration file as follows.

$ sudo mkdir -p /usr/local/nagios/etc/servers

Then create a configuration file for the remote host as follows. We have named out file ubuntu-host.cfg

$ sudo vim  /usr/local/nagios/etc/servers/ubuntu-host.cfg

Add the following configuration. Of course, you need to replace details such as hostname , alias, and address accordingly to match your host’s details.

define host  {
         use                                linux-server
         host_name                     hostname
         alias                               My database server
          address                         host-IP-address
         max_check_attempts          5
         check_period                    24x7
         notification_interval           30
         notification_period             24x7

Save and close the configuration file.

Lastly, edit the Nagios NRPE configuration file.

$ sudo vim /usr/local/nagios/etc/nagios.cfg

Uncomment the line below that points to the path of our host’s configuration file


Save and close. Then restart Nagios service.

$ sudo systemctl restart nagios.

Nagios listens to TCP port 5666. If UFW is running , you need to open it on both the Nagios server and remote host as follows.

$ sudo ufw allow 5666/tcp

Then reload it to apply changes.

$ sudo ufw reload

And that’s it.

When you visit the Nagios dashboard and click on ‘hosts’ tab on the left pane, your host will be displayed as shown below.

add a remote host to Nagios
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