To install Nagios on Ubuntu, follow these step-by-step commands based on the provided sources:

gistfile1.txt

To install Nagios on Ubuntu, follow these step-by-step commands based on the provided sources:

1. **Install Packages Dependencies**:
   - Update the Ubuntu repository:
     ```bash
     sudo apt update
     ```
   - Install necessary packages for Nagios installation:
     ```bash
     sudo apt install -y autoconf gcc make unzip libgd-dev libmcrypt-dev libssl-dev dc snmp libnet-snmp-perl gettext
     sudo apt install -y build-essential apache2 php openssl perl make php-gd libgd-dev libapache2-mod-php libperl-dev libssl-dev
     ```

2. **Install Nagios Core 4.4.6**:
   - Download Nagios Core 4.4.6 source code:
     ```bash
     cd ~
     wget https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.6.tar.gz
     ```
   - Extract the Nagios package and navigate to the extracted directory:
     ```bash
     tar -xf nagios-4.4.6.tar.gz
     cd nagioscore-*/
     ```
   - Configure and install Nagios Core:
     ```bash
     sudo ./configure --with-httpd-conf=/etc/apache2/sites-enabled
     sudo make all
     sudo make install-groups-users
     sudo usermod -a -G nagios www-data
     sudo make install
     sudo make install-daemoninit
     sudo make install-commandmode
     sudo make install-config
     sudo make install-webconf
     sudo a2enmod rewrite cgi
     systemctl restart apache2
     ```

3. **Create nagiosadmin User**:
   - After installing Nagios Core, create the nagiosadmin user for accessing the Nagios dashboard:
     ```bash
     sudo htpasswd /etc/nagios3/htpasswd.users nagiosadmin
     ```
     
     
     To install Nagios Plugins, you can follow these steps based on the provided sources:

1. **Install Nagios Plugins**:
   - Download the latest Nagios Plugins source code:
     ```bash
     wget http://www.nagios-plugins.org/download/nagios-plugins-2.4.3.tar.gz
     ```
   - Extract the downloaded Nagios Plugins package:
     ```bash
     tar xzf nagios-plugins-2.4.3.tar.gz
     ```
   - Navigate to the extracted directory:
     ```bash
     cd nagios-plugins-2.4.3
     ```
   - Configure the installation:
     ```bash
     sudo ./configure --with-nagios-user=nagios --with-nagios-group=nagcmd --with-openssl
     ```
   - Build and install the Nagios Plugins:
     ```bash
     sudo make
     sudo make install
     ```

By following these commands, you will successfully install Nagios Plugins, which are essential for monitoring various services and functionalities on your Nagios monitoring system.

Citations:
[1] https://ubuntu.com/server/docs/tools-nagios
[2] https://www.digitalocean.com/community/tutorials/how-to-install-nagios-4-and-monitor-your-servers-on-ubuntu-18-04
[3] https://tecadmin.net/install-nagios-monitoring-server-on-ubuntu/
[4] https://www.geeksforgeeks.org/how-to-install-nagios-on-ubuntu/
[5] https://www.howtoforge.com/tutorial/how-to-install-nagios-on-ubuntu-2004/

By following these commands, you can successfully install Nagios on your Ubuntu system and set up the necessary configurations for monitoring your servers and services.

Citations:
[1] https://www.digitalocean.com/community/tutorials/how-to-install-nagios-4-and-monitor-your-servers-on-ubuntu-18-04
[2] https://www.howtoforge.com/tutorial/how-to-install-nagios-on-ubuntu-2004/
[3] https://assets.nagios.com/downloads/nagioscore/docs/nagioscore/4/en/quickstart-ubuntu.html
[4] https://tecadmin.net/install-nagios-monitoring-server-on-ubuntu/
[5] https://ubuntu.com/server/docs/tools-nagios