Can you explain what Nagios is and what it is used for in a monitoring system?

Nagios is a monitoring system used to track the status of servers, network devices, services, and applications. It helps administrators receive notifications about infrastructure issues such as server unavailability, high load, service errors, etc.

Main features of Nagios:

• Monitoring the availability and performance of hosts and services.
• Configuring alerts (email, SMS, etc.) when problems occur.
• Visualizing system status through a web interface.
• Extensibility with plugins for checking various parameters.

Example: if a web server stops responding, Nagios will detect this and send a notification to the administrator so they can take prompt action.