Setting up Nagios Core in Ubuntu Server 16.10

This article defines the final procedure for installing and
configuring Nagios Core in Ubuntu Server 16.10 distributions.

First of all, make sure all steps described in this document are executed under root account.
In order to elevate, the following command must be submitted.

 sudo -i

Before anything else, install the required dependencies

 apt-get install wget unzip daemon build-essential apache2 php7.0-gd libgd2-xpm-dev libapache2-mod-php7.0 apache2-utils

Download Nagios Core and Nagios Plugins packets to your temporary files directory

 cd /tmp/

 wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.2.3.tar.gz

 wget https://nagios-plugins.org/download/nagios-plugins-2.1.4.tar.gz

Extract the compressed files and enter the Nagios Core generated folder

 tar zxvf nagios-4.2.3.tar.gz

 tar zxvf nagios-plugins-2.1.4.tar.gz

 cd nagios-4.2.3/

Set the default account parameters aggregating Nagios and Apache with nagcmd group

 useradd nagios

 groupadd nagcmd

 usermod -a -G nagcmd nagios

 usermod -a -G nagcmd www-data

Run the setup script and proceed with the components installation

 ./configure --with-nagios-group=nagios --with-command-group=nagcmd --with-mail=/usr/bin/sendmail

 make all && make install

 make install-init

 make install-config

 make install-commandmode

 /usr/bin/install -c -m 644 sample-config/httpd.conf /etc/apache2/sites-enabled/nagios.conf

Activate the CGI and rewrite modules, and restart Apache.

 a2enmod cgi

 a2enmod rewrite

 service apache2 restart

Access Nagios Plugins folder and finish the standard system installation.

 cd ../nagios-plugins-2.1.4/

 ./configure --with-nagios-user=nagios --with-nagios-group=nagios

 make && make install

Create the default user for WEB access and launch Nagios service.

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

 /etc/init.d/nagios start

Ensure the necessary services are loaded at startup.

 ln -s /etc/init.d/nagios /etc/systemd/system/multi-user.target.wants/nagios.service

 systemctl enable apache2

 systemctl daemon-reload

After successfully completing the procedures, the Nagios Core web interface installation must be available.
In order to access it, browse to: http://server_ip/nagios

When prompted, just authenticate with the credentials designated to your web account (user: nagiosadmin, in this case).

For any troubleshooting regarding these steps, sign up to the global board: http://support.nagios.com/forum/

Additionally, refer to the official Nagios Core documentation found at: http://library.nagios.com/library/products/nagioscore/manuals/