Pre-requisites:

• SELinux (Passive mode):

sudo sed -i 's/SELINUX=.*/SELINUX=permissive/g' /etc/selinux/config
sudo setenforce 0

Step 1: Installing Dependencies

Update your system.

sudo dnf updates

Install required Dependencies.

sudo dnf install @php

sudo dnf install @perl @httpd wget unzip glibc automake glibc-common gettext autoconf php php-cli gcc gd gd-devel net-snmp openssl-devel unzip net-snmp postfix net-snmp-utils

Guide for Installing Development Tools on RHEL 8 / Cento 8.

sudo dnf groupinstall "Development Tools"

Now, start and enable httpd and php-fpm services.

sudo systemctl enable --now httpd php-fpm

Checki status is running.

systemctl status http php-fpm

Detailed instructions for the Installation of PHP and httpd.

Step 2: Downloading Nagios Core

Change directory to /usr/src/. Go to latest-release page of Nagios to download.

sudo su -
cd /usr/src

Create nagios-$VER directory.

Download & extract Nagios tarball.

https://github.com/NagiosEnterprises/nagioscore/releases

Change path to created folder.

cd nagios-$VER

Step 3: Compile Nagios Core on Centos 8 / RHEL 8.

a. Run the configure script by command below:

./configure

Output:

b. To compile the main program and CGIs, run the make command with all options.

sudo make all

Output:

c. Create User And Group

This will create user and groups in Nagios

Add apache user to Nagios Group.

make install-groups-users
usermod -a -G nagios apache

d. Install Nagios on Centos / RHEL 8.

Install Nagios base.

make install

e. Install the init script in /lib/systemd/system.

make install-init

f. Install and configure the permissions on the directory for holding the external command file.

make install-commandmode

g. Install sample config files in /usr/local/nagios/etc.

make install-config

h. Install the Apache config file for the Nagios web interface.

make install-webconf

i. Install the Exfoliation theme for the Nagios web interface.

make install-exfoliation

j. You can install classic theme for Nagios web interface by given command

make install-classicui

Step 4: Creating Nagios Web User

We need to create a user account for Nagios web interface . Use the given command:

sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Restart Apache services to take effect.

systemctl restart httpd

Step 5: Installing Nagios Plugins

Plugins are used to provide more monitoring features.
Switch to /usr/src directory.

cd /usr/src

Create new directory as nagios-plugins-$VER

mkdir nagios-plugins-$VER

Download Nagios plugins from Github releases page.

Extract it to /usr/src/nagios-plugins-$VER directory.

Now, change directory to nagios-$VER.

cd 'nagios-$VER'

Use this command to install and compile Nagios Plugins.

./configure --with-nagios-user=nagios --with--nagios-group=nagios
make && make install

Output:

Step 6: Verifying Installation & Starting Nagios Services.

Make sure your Nagios installation is working properly.

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

Start & Enable Nagios service to start at boot.

sudo systemctl enable --now nagios

Re-check the service status.

systemctl status nagios

Step 7: Accessing Nagios Web Dashboard

Remove firewall restrictions:

sudo firewall-cmd --permanent --add-service={http,https}
sudo firewall-cmd --reload

Access Dashboard by visiting http:[IP/hostname]/nagios/
Fill out Authentication details:

Username: nagiosadmin

You can add device to be monitored in Dashboard.

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