The OpenStack Image Service enables users to discover, register, and retrieve virtual machine images. Also known as the glance project, the Image Service offers a REST API that enables you to query virtual machine image metadata and retrieve an actual image. You can store virtual machine images made available through the Image Service in a variety of locations from simple file systems to object-storage systems like OpenStack Object Storage. For simplicity, this guide configures the Image Service to use the file back end. This means that images uploaded to the Image Service are stored in a directory on the same system that hosts the service. By default, this directory is /var/lib/glance/images/. Before you proceed, ensure that the system has sufficient space available in this directory to store virtual machine images and snapshots. At an absolute minimum, several gigabytes of space should be available for use by the Image Service in a proof of concept deployment. To see requirements for other back ends, see Configuration Reference.