How To Install NRPE on CentOS/RHEL 9/8/7

If you’re looking to monitor your CentOS/RHEL servers using Nagios, you’ll need to install the NRPE (Nagios Remote Plugin Executor) service. NRPE allows Nagios to execute plugins on remote hosts and monitor their health status.

In this article, we’ll walk you through the process of installing Nagios Remote Plugin Executor on CentOS/RHEL 9/8/7.

To see how to install this agent on Ubuntu, click here.

Prerequisites

Before you begin, make sure you have the following prerequisites:

• A CentOS/RHEL 9/8/7 server with root access
• Internet connectivity

Step 1: Install EPEL Repository

First, we need to install the EPEL (Extra Packages for Enterprise Linux) repository, which contains the NRPE package.

To install EPEL, run the following command :

[root@Linux ~]# dnf install epel-release

For RHEL 8/9 use dnf command instead.

Run the following command to check if the repository is added successfully :

[root@Linux ~]# yum repolist

Step 2: Install NRPE

Now that the EPEL repository is installed, we can install the NRPE package using the following command :

[root@Linux ~]# yum install nrpe nagios-plugins-nrpe -y 

Step 3: Configure NRPE

After installing our agent, we need to configure it to communicate with Nagios. We’ll need to edit the nrpe.cfg file to specify the Nagios server’s IP address and define the plugins to execute.

[root@Linux ~]# vi /etc/nagios/nrpe.cfg

Locate the following lines in the file :

allowed_hosts=127.0.0.1,::1

Replace the allowed_hosts line with the IP address of your Nagios server, like this:

allowed_hosts=192.168.5.2

Then, command lines to define the plugins to execute. For exemple to define a command to check the load average, users and disk usage, you would add the following line :

command[check_load]=/usr/lib64/nagios/plugins/check_load -w 15,10,5 -c 30,25,20
command[check_users]=/usr/lib64/nagios/plugins/check_users -w 5 -c 10
command[check_disk]=/usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/sda1

Step 4: Start NRPE

Now that Nagios agent is installed and configured, we can start the service and enable it to start automatically at boot :

[root@Linux ~]# systemctl start nrpe
[root@Linux ~]# systemctl enable nrpe

Step 5: Configure Firewall

If you’re running a firewall on your server, you’ll need to allow incoming traffic on port 5666, which NRPE uses to communicate with Nagios.

[root@Linux ~]# firewall-cmd --add-port=5666/tcp --permanent
[root@Linux ~]# firewall-cmd --reload

Step 6: Verify Installation

To verify that the Nagios agent is installed and working correctly, run the following command :

[root@Linux ~]# /usr/lib64/nagios/plugins/check_nrpe -H 127.0.0.1

If the NRPE configuration is correct, the output should be similar to the following :

NRPE v4.1.0

Also, you can use the check_nrpe plugin on the Nagios server to execute a plugin on the remote server :

[root@Linux ~]# /usr/lib64/nagios/plugins/check_nrpe -H 192.168.5.101 -c check_load

If Nagios agent is installed and configured correctly, you should see output similar to the following :

OK - load average: 0.00, 0.01, 0.05|load1=0.000;15.000;30.000;0; load5=0.010;10.000;25.000;0; load15=0.050;5.000;20.000;