Do you dream of spinning up ten, twenty, or a thousand virtual machines in an instant? Discover and repair bottlenecks without moving a finger? Dodge the loss of an entire storage array with no-one noticing? During this tutorial, we will demonstrate how to leverage FOSS and Linux tools to build a powerful, scalable cloud that easily competes with proprietary solutions.The tutorial is aimed at those interested in building clouds and uses Xen and CloudStack as examples to get started. You will leave with a collection of pre-made tools that you can use right out of the box or modify to your liking. You will also leave with immediately useful knowledge on best practices and common pitfalls covering areas such as security, multi-tenancy and others. Tools discussed include Xen, XCP. Open vSwitch, OpenStack, CloudStack and DevOps tools such as Chef, Puppet and Juju.