Docker/Storage

This lesson introduces Docker storage.

Objectives and Skills
Objectives and skills for this lesson include:
 * State which graph driver should be used on which OS
 * Demonstrate how to configure devicemapper
 * Compare object storage to block storage, and explain which one is preferable when available
 * Summarize how an application is composed of layers and where those layers reside on the filesystem
 * Describe how volumes are used with Docker for persistent storage
 * Identify the steps you would take to clean up unused images on a filesystem, also on DTR
 * Demonstrate how storage can be used across cluster nodes
 * Identity roles
 * Describe the difference between UCP workers and managers
 * Describe process to use external certificates with UCP and DTR (UCP from cli, from GUI, print the public certificates), DTR)