Compute relies on an external image service to store virtual machine images and maintain a catalog of available images. By default, Compute is configured to use the OpenStack Image Service (Glance), which is currently the only supported image service. If your installation requires euca2ools to register new images, you must run the nova-objectstore service. This service provides an Amazon S3 front-end for Glance, which is required by euca2ools. You can modify many options in the OpenStack Image Service. The following tables provide a comprehensive list.