add-apt-repository is an unknown command in minimal Ubuntu installs (like on servers)
On 12.04, running sudo apt-get install python-software-properties helped. In 12.10 I'm told to use sudo apt-get install software-properties-common http://muffinresearch.co.uk/archives/2011/08/31/ubuntu-add-apt-repository-command-not-found/ Stephan
