The document discusses cloud computing and provides an overview of its key concepts and models including Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a Service (IaaS). It also covers public and private clouds as well as the benefits and challenges of cloud computing. The role of grid computing technologies in cloud computing is examined. Details are given on the open-source cloud computing platform Eucalyptus including its architecture, sample setups, and security issues. A comparison is provided of other cloud software such as OpenNebula, Nimbus, CloudStack, and OpenStack. Steps are outlined for installing and configuring Eucalyptus and managing its nodes and images.