Icinga is an umbrella term or brand name for a monitoring system built from several more or less independent components. Functionally the whole Icinga system (actively) monitors systems or services, stores the results of this monitoring activity, visualizes this data for the human operators and also notifies them if things go pear-shaped.

The most prominent components are briefly explained in the following section:

  • Icinga 2 is the core program of most setups. A service daemon, which acts as a, possibly distributed, scheduler to execute little programs, called Monitoring Plugins, to test or discover certain properties of components in the IT environment. The last sentence is intentionally rather vague as to what exactly Icinga 2 does, but the detailed description has its place in the specific documentation[CITATION NEEDED].

For now the basics are:

* Icinga 2 receives some configuration and will execute "checks" to monitor things and
  write the result to a storage backend (IcingaDB or IDO)
* Icinga 2 instances communicate with each other via network in a tree like organisation,
  where an instance at the top (root) will configure other instances (to execute "checks")
  and receive the results of their monitoring activity in response

  • Icinga Web 2 (Icinga Web) is a web interface (framework) which implements important basic functionality (e.g. user management, roles for permission management) which can be harnessed by Modules. These Modules then implement the visualisation of monitoring activities (“IcingaDB Web” or the “monitoring” module), perform monitoring activities themselves (e.g. the “x509” or the “vSphereDB” module) or the graphical configuration of Icinga 2 (the “Icinga Director”).

  • IcingaDB The umbrella term for the current storage backend for Icinga 2 as well as the daemon program which represents part of the implementation.

  • IDO (Icinga Data Output) The old (legacy) storage backend for Icinga 2. This component is deprecated!

  • Icinga Director A module for Icinga Web 2 with the purpose of providing a more accessible way to configure Icinga 2. This is likely the most common way to generate configuration (although not the only one). The director also provides data import and manipulation functionality to generate the monitoring configuration in an automatic way which is helpful or even necessary in bigger setups.

  • Icinga for Windows is again an umbrella term for different components which handle the installation and management of Icinga components on Windows machines in a setup and also provide functionality to monitor those machines.