Ubuntu

curl -sSL https://get.daocloud.io/docker | sh

Solution (from https://docs.docker.com/engine/installation/linux/debian/, does not only work with Debian):

Add the docker group if it doesn't already exist.
sudo groupadd docker

Add the connected user "${USER}" to the docker group.
Change the user name to match your preferred user.
You may have to logout and log back in again for
this to take effect.
sudo gpasswd -a ${USER} docker

Restart the Docker daemon.
sudo service docker restart