Nagios, now known as Nagios Core, is a free and open source computer-software application that monitors systems, networks and infrastructure.

Nagios offers monitoring and alerting services for servers, switches, applications and services.

It alerts users when things go wrong and alerts them a second time when the problem has been resolved.

Network monitoring is the use of a system that constantly monitors a computer network for slow or failing components and that notifies the network administrator (via email, SMS or other alarms) in case of outages or other trouble.

Network monitoring is part of network management.

The open-source model is a decentralized development model that encourages open collaboration.

A main principle of open-source software development is peer production, with products such as source code, blueprints, and documentation freely available to the public.

The open-source movement in software began as a response to the limitations of proprietary code.

The model is used for projects such as in open-source appropriate technologies, and open-source drug discovery.

In computing, a server is a computer program or a device that provides functionality for other programs or devices, called "clients".

This architecture is called the client–server model, and a single overall computation is distributed across multiple processes or devices.

Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients, or performing computation for a client.

A single server can serve multiple clients, and a single client can use multiple servers.

A client process may run on the same device or may connect over a network to a server on a different device.

Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers.

Enterprise software, also known as enterprise application software (EAS), is computer software used to satisfy the needs of an organization rather than individual users.

Such organizations would include businesses, schools, interest-based user groups, clubs, charities, or governments.

Enterprise software is an integral part of a (computer-based) information system.