Then list images with docker images -a:
An option is listing the Containers with docker ps -a:
To remove Containers, we can do: docker rm container-id
For example, in order to remove the first container: rm container e609f1563ca8
To remove images, we can do: docker rmi [press TAB key twice], available images will appear, if we type initial letters of the image we need removing pressing the TAB key will auto complete the image's name.
In my case: docker rmi karthequian/gruyere:latest
Now, we can to turn-off the docker service with: "sudo service docker stop"
That's it.