Cloud computing has become the most important terminology in the computing sphere. It has reduced the effort and cost required to set up and operate the overall computing infrastructure. It has helped various businesses quickly start their business operations without wasting time planning their IT infrastructure, and has enabled really small teams to scale their businesses with on-demand computing power.

The term cloud is commonly used to refer to a large network of servers connected to the Internet. These servers offer a wide range of services and are available for the general public on a pay-per-use basis. Most cloud resources are available in the form of Software as a Service (SaaS), Platform as a Service (PaaS), or Infrastructure as a Service (IaaS). A SaaS is a software system hosted in the cloud. These systems are generally maintained by large organizations; a well-known example that we commonly use is Gmail and the Google Docs service. The end user can access these application through their browsers. He or she can just sign up for the service, pay the required fees, if any, and start using it without any local setup. All data is stored in the cloud and is accessible from any location.

PaaS provide a base platform to develop and run applications in the cloud. The service provider does the hard work of building and maintaining the infrastructure and provides easy-to-use APIs that enable developers to quickly develop and deploy an application. Heroku and the Google App Engine are well-known examples of PaaS services.

Similarly, IaaS provides access to computing infrastructure. This is the base layer of cloud computing and provides physical or virtual access to computing, storage, and network services. The service builds and maintains actual infrastructure, including hardware assembly, virtualization, backups, and scaling. Examples include Amazon AWS and the Google Compute Engine. Heroku is a platform service built on top of the AWS infrastructure.

These cloud services are built on top of virtualization. Virtualization is a software system that enables us to break a large physical server into multiple small virtual servers that can be used independently. One can run multiple isolated operating systems and applications on a single large hardware server. Cloud computing is a set of tools that allows the general public to utilize these virtual resources at a small cost.

Ubuntu offers a wide range of virtualization and cloud computing tools. It supports hypervisors, such as KVM, XEN, and QEMU; a free and open source cloud computing platform, OpenStack; the service orchestration tool Juju and machine provisioning tool MAAS. In this chapter, we will take a brief look at virtualization with KVM. We will install and set up our own cloud with OpenStack and deploy our applications with Juju.