Nagios is an open source application that monitors for computer network problems so that they can be fixed more quickly. Nagios was designed for use with the Linux operating system, but it will also work under Unix and most Unix-based systems.
Nagios runs periodic checks on user-specified resources and services. Resources that can be monitored include memory usage, disk usage, microprocessor load, the number of currently running processes, and log files. Services that can be monitored include Simple Mail Transfer Protocol (SMTP), Post Office Protocol 3 (POP3), Hypertext Transfer Protocol (HTTP), and other common network protocols. The program can monitor environmental variables such as temperature, humidity, or barometric pressure in conjunction with the appropriate measuring hardware. A user-friendly Web-based graphical user interface is provided. An authorization system allows the administrator to restrict access as necessary.
Nagios has proven popular among small businesses. Other users include Internet service providers (ISPs), educational institutions, government agencies, health care institutions, manufacturing companies, and financial institutions. Previously called NetSaint, Nagios was developed by Ethan Gelstad and refined by numerous contributors..