Shifter is a prototype implementation that NERSC is developing and experimenting with as a scalable way of deploying containers in an HPC environment. It works by converting user or staff generated images in Docker, Virtual Machines, or CHOS (another method for delivering flexible environments) to a common format. This common format then provides a tunable point to allow images to be scalably distributed on the Cray supercomputers at NERSC. The user interface to shifter enables a user to select an image from their dockerhub account and then submit jobs which run entirely within the container.