How to install ROS Hydro but keep Groovy?

edit

Let's assume your hydro workspace is /home/username/workspace/ros_hydro/catkin

If you have troubles with hydro interfering your groovy installation:

• edit your ~/.bashrc (if gedit is your editor of choice it'd be gedit ~/.bashrc) and remove lines such like source /opt/ros/hydro/setup.bash or source /home/username/workspace/ros_hydro/catkin/devel/setup.bash
• Now you still have a hydro installation and workspace around but it is no longer sourced so it will not be found by any ros command or build system. If you might whish to recover your hdyro system in the future this would be a good state.

If you really whish to completely uninstall ros hydro:

• delete your hydro workspace (using the assumption I'd be cd /home/username/workspace/ and rm -r ros_hydro)
• all hydro apt packages are named ros-hydro-whatever-package. You can remove them all by sudo apt-get remove ros-hydro*. Likely a sudo apt-get autoremove will be needed after this....

(No warranties for last two steps;) )