install docker on Debian

Per default, the docker commands can only be run by root, in order to allow another user to fully operate docker you need to make the following changes.

// add your user to docker usergroup
$ sudo usermod -aG docker yourusername

// to make this effective login/logout or start a new terminal session with:
$ su yourusername

// test-1 (should see the docker usergroup listed here):
$ id yourusername

// test-2:
$ docker info