I am running 14.04, but I need to run some corporate software/scripts that have been specifically designed for 12.04. I am aware of virtual box/vmware for full virtualization but I am looking for something more lightweight (on my windows machine both come at a significant cost in battery life) closer to os virtualization level. Ideally, I would like something like windows 7/8 compatibility mode: the ability to run a program as if I were on 12.04. Does Ubuntu/Linux have such mechanism? What is the preferred way of running programs/scripts designed for an older version of Ubuntu?