Uninstall docker
To remove just docker package itself from Ubuntu 16.04 (Xenial Xerus) execute on terminal:
sudo apt-get remove docker
Uninstall docker and it’s dependent packages
To remove the docker package and any other dependant package which are no longer needed from Ubuntu Xenial.
sudo apt-get remove --auto-remove docker
Purging docker
If you also want to delete configuration and/or data files of docker from Ubuntu Xenial then this will work:
sudo apt-get purge docker
To delete configuration and/or data files of docker and it’s dependencies from Ubuntu Xenial then execute:
sudo apt-get purge --auto-remove docker