Nagios is an open source monitoring system for computer systems. It was designed with core components to run on the Linux operating system and can monitor devices running Linux, Windows and Unix OSes.
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Nagios runs periodic checks on critical parameters of application, network and server resources. It can monitor, for example, memory usage, disk usage, microprocessor load, the number of currently running processes and log files. Nagios also can monitor services, such as Simple Mail Transfer Protocol (SMTP), Post Office Protocol 3 (POP3), Hypertext Transfer Protocol (HTTP) and other common network protocols. Active checks are initiated by Nagios, while passive checks come from external applications connected to the monitoring tool.
Nagios is organized as a pluggable, open source tool, which makes it easy to develop new components for it and to extend its functionality. At the heart of Nagios is its server, where plug-ins and add-ons allow the user to define targets and which parameters on these targets to monitor. For example, when used in conjunction with environmental-sensing systems, Nagios can share data on environmental variables, such as temperature, humidity or barometric pressure.
Nagios can also run remote scripts by using the Nagios Remote Plugin Executor, also called NRPE.
Nagios runs in agent-based and agentless configurations. The user can install a Nagios monitoring agent on any resource they wish to track, or rely on agentless monitoring protocols to track performance. The choice between agent-based and agentless monitoring depends on the design of the IT infrastructure and desired monitoring setup.
A user-friendly, web-based graphical user interface is provided in some versions of Nagios and from third parties, or an administrator can choose to work in the command-line interface. It also comes with a dashboard that provides an overview of the critical parameters monitored on assets.
The service that was originally known as Nagios is now referred to as Nagios Core. Nagios XI is the extended interface, proposed as the enterprise-level version of the monitoring tool. Nagios Core is available free, while Nagios XI must be purchased from Nagios Enterprises. Other commercial extensions of Nagios include Nagios Log Server, Nagios Network Analyzer and Nagios Fusion:
- Nagios Log Server provides log management, monitoring and analysis.
- Nagios Network Analyzer tracks network traffic and bandwidth utilization.
- Nagios Fusion is an aggregation service for Nagios Core and Nagios XI servers, showing multiple servers in one view.
Based on the parameters and thresholds defined, Nagios can send out alerts if critical levels are reached. These notifications can be sent in different ways, including email and text messages. An authorization system allows the administrator to restrict access.
Nagios has proven popular among small and large businesses, as well as internet service providers, educational institutions, government agencies, healthcare institutions, manufacturing companies and financial institutions. Previously called NetSaint, Nagios was developed by Ethan Galstad and refined by numerous contributors as an open source project.