In this talk we will discuss how the build system and QA of CentOS is implemented using a private cloud: OpenNebula. We will focus on the challenges of integration, advantages and workflow. We will also demonstrate how to implement and automate a building system and QA tasks by creating a private cloud on the fly with a CentOS laptop using OpenNebula. Administrators will benefit from this technique -and its simplicity and ease of deployment- to overcome the complexity of this kind of systems.