Nagios is a powerful tool for monitoring your IT infrastructure. It helps keep track of system performance and alerts you to any issues. In this guide, we’ll walk you through how to install and configure the Nagios NRPE (Nagios Remote Plugin Executor) client on Ubuntu 24.04. We’ll also show you how to add a host on the Nagios server for monitoring.

What You Need

  • A server running Ubuntu 24.04
  • Nagios server already set up and running
  • Basic understanding of Linux commands

Step 1: Update Your System

First, make sure your system is up to date. Open the terminal and run:

sudo apt update
sudo apt upgrade

Step 2: Install Nagios NRPE Client

Install the NRPE client and Nagios plugins by running:

sudo apt install nagios-nrpe-server nagios-plugins

Step 3: Configure NRPE

Edit the NRPE configuration file to allow connections from your Nagios server. Open the file using a text editor:

sudo nano /etc/nagios/nrpe.cfg

Find the line that starts with allowed_hosts and add your Nagios server IP address. It should look like this:


allowed_hosts=127.0.0.1,

Save and close the file (press CTRL X, then Y, and Enter).

Step 4: Start and Enable NRPE Service

Start the NRPE service and enable it to start on boot:

sudo systemctl start nagios-nrpe-server
sudo systemctl enable nagios-nrpe-server

Step 5: Verify NRPE Configuration

Ensure NRPE is working correctly by running the following command from your Nagios server. Replace with the IP address of your Ubuntu server:

/usr/lib/nagios/plugins/check_nrpe -H

You should see a response like this:


NRPE v4.0.3

Step 6: Add Host to Nagios Server

Now, let’s add the Ubuntu server as a host in Nagios for monitoring.

  1. Create a Host Configuration File

    On your Nagios server, create a configuration file for the new host. For example:

    sudo nano /usr/local/nagios/etc/servers/ubuntu24.cfg
  2. Add Host Configuration

    Add the following configuration to the file. Replace and with appropriate values.

    
define host {
	use                             linux-server
	host_name                       
	alias                           Ubuntu 24.04 Server
	address                         
	max_check_attempts              5
	check_period                    24x7
	notification_interval           30
	notification_period             24x7
}
  3. Add Service Configuration

    To monitor services like disk usage, CPU load, and memory usage, add the following configuration in the same file:

    
define service {
	use                             generic-service
	host_name                       
	service_description             Check Disk
	check_command                   check_nrpe!check_disk
}

define service {
	use                             generic-service
	host_name                       
	service_description             Check Load
	check_command                   check_nrpe!check_load
}

define service {
	use                             generic-service
	host_name                       
	service_description             Check Memory
	check_command                   check_nrpe!check_mem
}
  4. Restart Nagios

    Restart the Nagios service to apply the changes:

    sudo systemctl restart nagios

Conclusion

You have successfully installed and configured the Nagios NRPE client on Ubuntu 24.04. You also added your Ubuntu server as a host on the Nagios server for monitoring. Now, Nagios will keep an eye on your server’s health and alert you if anything goes wrong.

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