In this topic we’ll learn how to install and configure the latest official version of Nagios Core from sources in Debian and Ubuntu servers. Nagios Core is a free Open Source network monitoring application designed for monitoring network applications, devices and their related services and in a network. Nagios can remotely monitor specific operating system parameters via agents deployed on nodes and send alerts via mail or SMS in order to notify administrators in case critical services in a network, such as SMTP, HTTP, SSH, FTP and other fails. Requirements Debian 9 Minimal Installation Ubuntu 16.04 Minimal Installation Step 1: Install Pre-requirements for Nagios 1. Before installing Nagios Core from sources in Ubuntu or Debian , first install the following LAMP stack components in your system, without MySQL RDBMS database component, by issuing the below command. # apt install apache2 libapache2-mod-php7.0 php...