ROS Installation Hydro
From wikidb
Repository Set Up
See Repository Settings. "Note: In Ubuntu 9.04 (Jaunty) and later, the main, universe, restricted and multiverse repositories are enabled by default."
This was confirmed with the Main Menu: Ubuntu Software Center. "univere", "restricted" and "multiverse" were checked in the "Ubuntu Software" tab.
sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu precise main" > /etc/apt/sources.list.d/ros-latest.list' wget http://packages.ros.org/ros.key -O - | sudo apt-key add -