Nagios is a powerful open-source monitoring tool that allows you to monitor your network and systems. Here's a basic guide on how to install Nagios on Ubuntu:

Prerequisites

An Ubuntu server
A user with sudo privileges
Basic understanding of the command line

Install Nagios dependency packages

Update your package list and install the necessary dependencies.

sudo apt update
sudo apt install -y build-essential libgd-dev openssl libssl-dev unzip apache2 php libapache2-mod-php php-gd

Create a Nagios user and group

Create a user and group for Nagios.

sudo useradd nagios
sudo groupadd nagcmd
sudo usermod -a -G nagcmd nagios
sudo usermod -a -G nagcmd www-data

Download and compile Nagios by obtaining the source files and building them on your system.

Download and extract the latest Nagios Core release.

wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.5.8.tar.gz
tar xzf nagios-4.5.8.tar.gz
cd nagios-4.5.8

Configure and compile Nagios by running the necessary commands.

./configure --with-nagios-group=nagios --with-command-group=nagcmd
make all

Install Nagios by updating your package list, installing dependencies, creating a user and group, downloading the latest release, and compiling it.

Install Nagios binaries, init scripts, and command mode.

sudo make install
sudo make install-init
sudo make install-commandmode
sudo make install-config
sudo make install-webconf

To install Nagios plugins, download the plugin package, extract it, configure it, and then compile and install it.

Download and install Nagios plugins

wget https://nagios-plugins.org/download/nagios-plugins-2.4.9.tar.gz
tar xzf nagios-plugins-2.4.9.tar.gz
cd nagios-plugins-2.4.9
./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
sudo make install

Set up Apache on Ubuntu

Enable Apache modules and restart the service.

sudo a2enmod rewrite
sudo a2enmod cgi
sudo systemctl restart apache2

Set up the Nagios web interface on Ubuntu.

Create a Nagios admin user for the web interface.

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

Start the Nagios service on Ubuntu

Start and enable the Nagios service.

sudo systemctl start nagios
sudo systemctl enable nagios

Access the Nagios web interface on Ubuntu

Open your web browser, go to http://<IP of Instance>/nagios, and log in with the username nagiosadmin and the password you set earlier.

You can monitor using the console.

Installation Nagios on Ubuntu