Open Build Service is an open source project to build packages and even whole distributions. It is mainly used by openSUSE, but also by Tinzen and others. Talk will start with generic overview of what it can do, what are the strong sides, mention few weak sides and also some of the ugly hacks that we use in our (not related to openSUSE) project. Also just for the fun of it, we tried to recompile whole CentOS on OBS to see how far would it go with minimum effort, so results of this simple experiment will be part of the presentation.