One of the feature differences between hypervisors and containers is the ability to store a virtual machine image in a single file, since most containers exist as a chroot within the host OS rather than as fully independent entities. However, the ability to save and restore state in a machine image file is invaluable in managing virtual machine lifecycles in the data centre. This talk will début a new loopback device which gives all the advantages of virtual machine images by storing the container in a file while preserving the benefits of sharing significant portions with the host OS. We will compare and contrast the technology with the traditional loopback device and LVM, and describe a few features of a new loopback useful in container snapshotting and live migration. This talk will be technical in nature but should be accessible to people interested in cloud, virtualisation and container technologies.