How to Install Nagios 4 in Ubuntu and Debian

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 of critical services in a network, such as SMTP, HTTP, SSH, FTP, and other fails.

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