Free Software distributions, like Debian, RedHat, or Ubuntu, are some of the largest component based software systems, and they all use packages as their building blocks, together with tools for selecting, installing and removing packages on a running system.Evolving such complex software systems is a daunting task that carries significant challenges: in this talk, after providing a simple formalisation of packages and distributions, we will survey some recent results and algorithms developed to answer questions like "which is the most important package among the 27000 ones in Debian squeeze?", or "what version change is most likely to have an impact on the system"?