Would you love to get Docker up and running on you Raspberry Pi 2? Fortunately someone already did most of the leg work for you, as you will see from the article "Kick-Ass Raspberry Pi 2 having a forbidden love affair with Docker 1.4.1".
Check the official article "Installing Operating System Images" for more information on how to install this Debian Wheezy OS.
After you have downloaded and installed the image referenced in the article you're ready to do some adjustments to improve security.
Log in as root to create a personal user and give it a password: