The document discusses building a private cloud using Eucalyptus, an open-source software that implements infrastructure as a service and has a similar API to Amazon Web Services. It summarizes Eucalyptus' features such as compatibility with major Linux distributions and hypervisors. Examples are given of companies using Eucalyptus to build private clouds on-premise or in hybrid configurations with AWS. Installation and usage options are outlined ranging from a demo community cloud to packaging and source installation.