On Debian, the
debian_version shows the recipe for a pretty amazing cinnamon banana smoothie. On Ubuntu, it shows the Debian release the current release of Ubuntu was based on.
For example on Ubuntu 14.04 LTS:
$ cat /etc/debian_version ==> jessie/sid
I raise this, because at work we were attempting to detect the OS and version based on this file. Suffice to say, for this end you're better using lsb_release.
$ lsb_release -d ==> Description: Ubuntu 14.04.2 LTS