Overview
We are entering an age of open cloud infrastructure and application portability. The applications/services are required to scale in/out as per demand and need to be executed in multiple host environment. For this applications are required to run within shell, and the shell/container needs to work across several hosts and be portable to any cloud environment.

Docker is a container-based software framework for automating deployment of applications, makes it easy to partition a single host into multiple containers. However, although useful, many applications require resources beyond a single host, and real-world deployments require multiple hosts for resilience, fault tolerance and easy scaling of applications.
Installtion
These instructions describe to setup latest version of Docker for Ubuntu 14.04 for not latest release from Docker. Following are the list of commands.

• sudo apt-get update
• sudo apt-get install docker.io
• sudo ln -sf /usr/bin/docker.io /usr/local/bin/docker
• sudo sed -i '$acomplete -F _docker docker' /etc/bash_completion.d/docker.io

To setup latest Docker release, add the Docker repository key to your local keychain and process the install commands

• $ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 36A1D7869245C8950F966E92D8576A8BA88D21E9
• $ sudo sh -c "echo deb https://get.docker.io/ubuntu docker main > /etc/apt/sources.list.d/docker.list"
• $ sudo apt-get update
• $ sudo apt-get install lxc-docker

After install the Docker you can search any community containers. For e.g if you need to search for any debian package,

• docker search debian