Upto date docker installation instructions are are available from the docker website.

​https://docs.docker.com/engine/installation/linux/ubuntulinux/

==Prerequisites by Ubuntu Version==

Ubuntu Xenial 16.04 (LTS) Ubuntu Wily 15.10 Ubuntu Trusty 14.04 (LTS)

For Ubuntu Trusty, Wily, and Xenial, it’s recommended to install the linux-image-extra-* kernel packages. The linux-image-extra-* packages allows you use the aufs storage driver.

To install the linux-image-extra-* packages:

1. Open a terminal on your Ubuntu host.

2. Update your package manager.

$ sudo apt-get update

3.Install the recommended packages.

$ sudo apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual

Go ahead and install Docker.

  sudo apt-get update

  sudo apt-get install apt-transport-https ca-certificates

  sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D

  sudo vi /etc/apt/sources.list.d/docker.list

  cd /etc/apt/

  ls
  cd sources.list.d/
  ls
  sudo vi /etc/apt/sources.list.d/docker.list
  cd /home
  ls
  cd si84/
  sudo apt-get update
  sudo apt-get purge lxc-docker
  apt-cache policy docker-engine
  sudo apt-get install linux-image-extra-$(uname -r)
  sudo apt-get update
  sudo apt-get install docker-engine
  sudo service docker start