This ubuntu image attempts to immitate a standard (non docker) ubuntu workstation.
It contains the essential packages pre-installed, and a non root user
(with sudo privileges) named ubuntu
$ docker run --rm -it dannyben/ubuntu
Since this image sets the user to ubuntu, if you need to execute commands
that require root access in your image, you need to use this pattern:
FROM dannyben/ubuntu
USER root
# root stuff goes here
USER ubuntu