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

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

Update your apt sources

Docker’s APT repository contains Docker 1.7.1 and higher. To set APT to use packages from the new repository:

1. Log into your machine as a user with sudo or root privileges.

2. Open a terminal window.

3. Update package information, ensure that APT works with the https method, and that CA certificates are installed.

$ sudo apt-get update

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

4. Add the new GPG key.

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

5. Open the /etc/apt/sources.list.d/docker.list file in your favorite editor.

If the file doesn’t exist, create it.

6. Remove any existing entries.

7. Add an entry for your Ubuntu operating system.

The possible entries are:

Ubuntu Xenial 16.04 (LTS)

deb https://apt.dockerproject.org/repo ubuntu-xenial main

8. Save and close the /etc/apt/sources.list.d/docker.list file.

9. Update the APT package index.

$ sudo apt-get update

10. Purge the old repo if it exists.

$ sudo apt-get purge lxc-docker

11. Verify that APT is pulling from the right repository.

$ apt-cache policy docker-engine

From now on when you run apt-get upgrade, APT pulls from the new repository.

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