How to install the nrpe (nagios client) for Ubuntu

How to install the nrpe (nagios client) for Ubuntu

Step 1
Install Nagios Client on Ubuntu

First, enter the terminal, open the server, and run the following command to install

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

Here nagios-nrpe-server package installs service on the system and nagios-plugins provide monitoring scripts, which are called with the NRPE client on request of the Nagios server.

Step 2

Configure Nagios Client

In NRPE configuration, first, we need to configure to which Nagios servers it accepts requests, For example, your Nagios server IP is 69.30.214.227, then add this IP to the allowed host's list. Edit NRPE configuration file /etc/nagios/nrpe.cfg and make the necessary changes like below:

 vi /etc/nagios/nrpe.cfg 
 allowed_hosts=127.0.0.1, nagois IP

Next, restart the NRPE service. Now it is ready to listen to requests from the Nagios server

 systemctl restart nagios-nrpe-server 

Step 3

Update Command Definitions for NRPE

You must have defined all the commands to be used by the Nagios server. Some of them are pre-configured with the installation. You may be required to change the command as per your system’s configuration. Also, you can add more customized commands to monitor your server.

Edit the /etc/nagios/nrpe.cfg configuration file and search for COMMAND DEFINITIONS sections. Here you can define or update check commands.

   vi /etc/nagios/nrpe.cfg 

Go to inside nrpe.cfg edit this type

 command[check_users]=/usr/lib/nagios/plugins/check_users -w 5 -c 10
 command[check_load]=/usr/lib/nagios/plugins/check_load -r -w 15,10,9 -c 30,20,18
 command[check_hda1]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /dev/hda1
 command[check_zombie_procs]=/usr/lib/nagios/plugins/check_procs -w 5 -c 10 -s Z
 command[check_total_procs]=/usr/lib/nagios/plugins/check_procs -w 150 -c 200
 command[check_disk]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /
 command[check_mem]=/usr/lib/nagios/plugins/check_mem -f -w 5 -c 2

Save the configuration file and restart the NRPE daemon to apply changes:

 systemctl restart nagios-nrpe-server 

Check nagios-nrpe-server status

 systemctl status nagios-nrpe-server 

Step 4

Allowing nrpe port

We need to allow the port below commands 

 ufw status
 ufw allow 5666