Nagios
Nagios is an open-source monitoring system that tracks the performance and availability of IT infrastructure components such as servers, networks, and applications. It provides alerting, reporting, and visualization features to help administrators detect and resolve issues proactively. Originally developed in 1999, it has become a widely used tool for system and network monitoring in enterprise environments.
Developers and IT operations teams should learn Nagios when they need a robust, customizable monitoring solution for on-premises or hybrid infrastructure, especially in environments where real-time alerting and historical data analysis are critical for uptime. It is particularly useful for monitoring servers, network devices, and services in large-scale deployments, as it supports plugins for extensive customization and integration with other tools.