Recently, I upgraded my Ubuntu (XFCE) 12.10 Quantal Quetzal to Ubuntu 13.04 Raring Ringtail. When I wanted to add many PPAs which was disabled when upgrading, I've got the following error message "sudo: add-apt-repository: command not found". The command commonly used to add repository especially from PPA (Personal Package Archive), many good Ubuntu applications have their own PPA, so it should be installed on Ubuntu to get a full fledged Ubuntu system. I'm surprised a little bit, because I think it was installed by default on Ubuntu. So, if you encountered the same problem, here's the fix.

If you do Google Search on that problem, you will get many suggestions to install "python-software-properties" package. Unfortunately, those solution doesn't work anymore on Ubuntu 12.10 Quantal Quetzal and above. The right solution is to install "software-properties-common" package.
  • sudo apt-get install software-properties-common
Done! Please try to add any PPA channel to Ubuntu, for example:
  • sudo add-apt-repository ppa:libreoffice/ppa

Good luck!