Wikipedia
OneSIS
oneSIS is an open-sourced software tool developed at Sandia National Laboratories aimed at easing systems administration in large-scale, Linux cluster environments.
The official tag line for oneSIS is that it is a thin, role-based Single Image System for scalable cluster management. oneSIS is a simple and highly extensible method for deploying and managing one or more root images of supported Linux distributions into a master image used as the root of diskless nodes. A single image can serve thousands of nodes.