Install Docker OS (Open Source) Engine on ubuntu. This assumes that `linux-image-extra-virtual` is already installed

install-docker-os-engine.sh

#!/bin/bash

apt-get update -y
apt-get install apt-transport-https ca-certificates -y
apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D

rm -f /etc/apt/sources.list.d/docker.list
echo "deb https://apt.dockerproject.org/repo ubuntu-trusty main" | tee /etc/apt/sources.list.d/docker.list
apt-get update -y

apt-get purge lxc-docker -y
apt-get install docker-engine -y
service docker start
usermod -a -G docker ubuntu