Install Docker on Ubuntu 14.04
First update the system.
$ sudo apt-get update
$ sudo apt-get -y upgrade
Add the recommended package for the current kernel.
$ sudo apt-get install linux-image-extra-$(uname -r)
Add the official key for Docker.
$ sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
Add the source to the sources.list.d and refresh the packages.
$ echo "deb https://apt.dockerproject.org/repo ubuntu-trusty main" | sudo tee /etc/apt/sources.list.d/docker.list
$ sudo apt-get update
Now you can install Docker.
$ sudo apt-get install docker-engine
Change the following in /etc/default/ufw:
DEFAULT_APPLICATION_POLICY="DROP"
becomes
DEFAULT_APPLICATION_POLICY="ACCEPT"
Restart the firewall.
$ sudo ufw reload
Create a Docker group and your current user to it to be able to connect to the Docker daemon.
$ sudo groupadd docker
$ sudo usermod -aG docker $USER
Login again to start using Docker. Now check if Docker is working.
$ sudo service docker start
$ sudo docker run hello-world
Hopefully this last step will download the image and run the container. If you are happy with the result, make it start automatically on system start.
$ sudo systemctl enable docker