The etckeeper program is a tool to let /etc be stored in a git, mercurial, brz or darcs repository. It hooks into APT to automatically commit changes made to /etc during package upgrades. It tracks file metadata that version control systems do 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.