Learning Nagios 3.0 is a comprehensive configuration guide to monitor and maintain your network and systems. It is a practical guide to setting up the Nagios 3.0 open source network monitoring tool, installing and configuring Nagios 3 on various operating systems. It will help understand system monitoring and how Nagios works. Nagios 3 is a system that watches to see whether hosts and services are working properly, and notifies users when problems occur. Nagios allows both the monitoring of services on its own, and the receipt of information about computer and service statuses from other applications. Nagios constantly checks other machines on your network and various services on those machines.