Glance as a registry of images

At launch, a generic virtual machine requires a prebuilt disk image to boot from—some kind of storage that holds the operating system using which the virtual machine will run. Traditionally, a new virtual machine is created with a form of installation media accessible to it. This could take the form of an ISO, optical device, or maybe some form of network-accessible media. Whatever media is provided, an operating system installation is the next step in this scenario. One of the purposes of cloud computing is to be able to quickly create disposable virtual instances. The tasks of running an operating system installation and spawning a virtual machine fast are polar opposites of each other. Cloud computing has removed the need for a per-instance operating system installation by creating what has come to be known as cloud images. Cloud images are simply pre-installed bootable disk images that have been sealed. A sealed disk image is a sparse file containing...