1. A system for building a customized virtual machine (VM) image, comprising: a set of available software packages; a selector to select a subset of the set of available software packages, the selected subset including at least a first package and a second package and omitting a non-included package; an image builder to build a VM image including the selected subset of the set of available software packages; and a validator to validate that the first package and the second package do not conflict at run-time.