etckeeper is a collection of tools to let /etc be stored in a git,
mercurial, bazaar or darcs repository. It hooks into apt to automatically
commit changes made to /etc during package upgrades. It tracks file
metadata that git does not normally support, but that is important for
/etc, such as the permissions of /etc/shadow. It's quite modular and
configurable, while also being simple to use if you understand the basics
of working with version control.