🌌Add a New Host For Monitoring Nagios (WebServer)

Configuration

WebServer

Install Prerequirement

apt update
apt install -y autoconf gcc libmcrypt-dev make libssl-dev dc build-essential gettext libdbd-mysql-perl

Download Source

cd /tmp
wget --no-check-certificate -O nagios-plugins.tar.gz https://github.com/nagios-plugins/nagios-plugins/archive/release-2.4.6.tar.gz
tar zxf nagios-plugins.tar.gz

Install and compile

cd nagios-plugins-release-2.4.6/
./tools/setup
./configure
make
make install

Install NRPE Daemon on Agent

apt install -y autoconf automake gcc libc6 libmcrypt-dev make libssl-dev

Download NRPE (nrpe-4.1.0)

cd /tmp
wget --no-check-certificate -O nagios-nrpe.tar.gz  https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-4.1.0/nrpe-4.1.0.tar.gz
tar zxf nagios-nrpe.tar.gz 

Configure script and compile NRPE

cd nrpe-4.1.0/
./configure --enable-command-args
sudo make all
sudo make install-groups-users
sudo make install
sudo make install-config
sudo make install-init

Update Agent NRPE Configuration\

nano /usr/local/nagios/etc/nrpe.cfg

line 61 : add ip 0.0.0.0 line 106 : add the NMS Nagios private server ip line 306 : add the script

## check_nrpe script for Web-Instance.

command[check_root]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /
command[check_ping]=/usr/local/nagios/libexec/check_ping -H <ip-private-host> -w 100.0,20% -c 500.0,60% -p 5
command[check_ssh]=/usr/local/nagios/libexec/check_ssh -4 <ip-private-host> 
command[check_http]=/usr/local/nagios/libexec/check_http <ip-private-host> 
command[check_apt]=/usr/local/nagios/libexec/check_apt

Start service NRPE

systemctl start nrpe.service
systemctl enable nrpe.service
systemctl status nrpe.service

NMS-Nagios

Check Target Connection

To see if check_nrpe on the Nagios server can connect to the NRPE agent on the remote host, run the following command on the Nagios Server.

/usr/local/nagios/libexec/check_nrpe -H <ip-private-host>

Create 2 New Files

cd /usr/local/nagios/etc
sudo touch hosts.cfg services.cfg

Edit File nagios.cfg

nano /usr/local/nagios/etc/nagios.cfg

# Define for host and service monitoring agent
cfg_file=/usr/local/nagios/etc/hosts.cfg
cfg_file=/usr/local/nagios/etc/services.cfg

Add the script above in lines 46-48

Edit file hosts.cfg

nano /usr/local/nagios/etc/hosts.cfg

## Default Linux Host Template ##
define host{
name                            linux-box               ; Name of this template
use                             generic-host            ; Inherit default values
check_period                    24x7
check_interval                  5
retry_interval                  1
max_check_attempts              10
check_command                   check-host-alive
notification_period             24x7
notification_interval           30
notification_options            d,r
contact_groups                  admins
register                        0
}

## Define Host - Web Instance
define host{
use                             linux-box               ; Inherit default values from a template
host_name                       <instance-name>         ; The name we're giving to this server
alias                           debian                  ; A longer name for the server
address                         <ip-priv-webserver>     ; IP address of Remote Linux host
}

Instance-Name = webserver ip-priv-webserver = 10.10.1.141

Edit File services.cfg

nano /usr/local/nagios/etc/services.cfg

define service{
        use                     generic-service
        host_name               <instance-name>
        service_description     Root
        check_command           check_nrpe!check_root
        }

define service{
        use                     generic-service
        host_name               <instance-name>
        service_description     APT
        check_command           check_nrpe!check_apt
        }



define service{
        use                     generic-service
        host_name               <instance-name>
        service_description     CPU Load
        check_command           check_nrpe!check_load
        }

define service{
        use                     generic-service
        host_name               <instance-name>
        service_description     Total Processes
        check_command           check_nrpe!check_total_procs
        }

define service{
        use                     generic-service
        host_name               <instance-name>
        service_description     Current Users
        check_command           check_nrpe!check_users
        }

define service{
        use                     generic-service
        host_name               <instance-name>
        service_description     SSH Monitoring
        check_command           check_nrpe!check_ssh
        }

## Script to check the status of the Web Server (HTTP Service)

define service{
        use                     generic-service
        host_name               <instance-name>
        service_description     HTTP
        check_command           check_nrpe!check_http
        }

Instance-Name = webserver

Check the Nagios configuration

Check the Nagios configuration file to see if there are errors.

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

if there are no configuration errors

Restart Service Nagios

systemctl restart nagios.service

---

Configuration is Completed

Open Browser

http://<ip-addr-pub-nagios>/nagios

username : nagiosadmin
password : nagiosadmin