Nagios 4.3.4: Adding Ubuntu 14.0/16.0/Debian Servers/Clients to Nagios Monitoring server

This article will help us to install Ubuntu Linux client connects using the NRPE (Nagios Remote Plugin Executor) which is used to execute on the client machines and sends the status of the services to the Nagios server.

Installing Dependencies and NRPE Client.

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

Configure NRPE Client on Ubuntu

We needed to edit the NRPE configuration file on the client machine for which Nagios servers accept requests if the Nagios server IP is 192.168.1.200, then add this IP to should be added to the allowed host’s list.

Edit NRPE configuration file using vi or any other editor /etc/nagios/nrpe.cfg

$ sudo vi /etc/nagios/nrpe.cfg

Find the below line and make changes below

allowed_hosts=127.0.0.1, 192.168.1.200

We can add any Nagios servers which are allowed to monitor the client with comma-separated.

Now we have to restart the NRPE service. Now it’s ready to listen to requests from the Nagios server

$ sudo /etc/init.d/nagios-nrpe-server restart

Verify Connection to NRPE Configuration.

Let’s go to your Nagios 4.3.4 server and verify that your Nagios server can communicate with NRPE client services properly.

Execute the following command from the Nagios server plugin directory, and we are assuming that your NRPE client-server IP is 192.168.1.100.

$ check_nrpe -H 192.168.1.100
NRPE v2.15

Add Commands in the NRPE client configuration file for monitoring the services.

$ sudo vi /etc/nagios/nrpe.cfg

command[check_users]=/usr/lib/nagios/plugins/check_users -w 5 -c 10
command[check_load]=/usr/lib/nagios/plugins/check_load -w 15,10,5 -c 30,25,20
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

Restart the NRPE client Services

Use the following commands to start/stop/restart NRPE client services.

Every time we do any changes in the configuration file we needed to restart the service

sudo service nagios-nrpe-server stop
sudo service nagios-nrpe-server start
sudo service nagios-nrpe-server restart

In order to monitor Linux clients, we needed to add these clients and edit 2 configuration files in the Nagios server

Login to the Nagios server

Step 1. Edit hosts.cfg file to add the Linux client and add the client configuration

# vi /usr/local/nagios/etc/hosts.cfg

define host{
use                             linux-box               ; Inherit default values from a template
host_name                  New linux    ; The name we're giving to this server
alias                           CentOS 6                ; A longer name for the server
address                      192.168.1.84            ; IP address of Remote Linux host
}

Step 2. Edit services.cfg file to add the Linux client host_name to the services which we want to monitor

#vi /usr/local/nagios/etc/services.cfg
define service{
       use                          generic-service
       host_name               Testbox,{ new_linux_machine_hostname_defined in hosts.cfg }
       service_description    CPU Load
       check_command       check_nrpe!check_load    
}
define service{
       use                     generic-service         host_name              Testbox
        service_description     0. UP-Time
        check_command           check_nrpe!check_uptime
        servicegroups                   Uptime  
        }
define service{

        use                     generic-service
         host_name              Testbox
        service_description     1. CPU Load
        check_command           check_nrpe!check_load
      
        }
define service{
        use                     generic-service
        host_name Testbox
        service_description     2. Total Processes
        check_command           check_nrpe!check_total_procs
        }
define service{
        use                             generic-service
        host_name                       Testbox
        service_description             4. Disk Drive Root Partition
        servicegroups                   Disk-Space
        check_command                   check_nrpe!check_disk
        }
define service{
        use                             generic-service
        host_name                       Testbox
        service_description             5. Memory Usage
       check_command                   check_nrpe!check_mem
        servicegroups                   Memory
         }

Needed to add the Hostname which is given in the hosts.cfg file for the services you want to monitor

Keywords: Nagios, Monitoring, Linux host, Adding Linux host, ubuntu client, Ubuntu NRPE