1.4.6. Image Service
The Image service acts as a registry for virtual disk images. Users can add new images or take a snapshot (copy) of an existing server for immediate storage. Snapshots can be used as back up or as templates for new servers. Registered images can be stored in the Object Storage service, as well as in other locations (for example, in simple file systems or external web servers).
The following image formats are supported:
- raw (unstructured format)
- aki/ami/ari (Amazon kernel, ramdisk, or machine image)
- iso (archive format for optical discs; for example, CDROM)
- qcow2 (Qemu/KVM, supports Copy on Write)
- vhd (Hyper-V, common for virtual machine monitors from VMWare, Xen, Microsoft, VirtualBox, and others)
- vdi (Qemu/VirtualBox)
- vmdk (VMWare)
Container formats can also be used by the Image service; the format determines the type of metadata stored in the image about the actual virtual machine. The following formats are supported.
- bare (no metadata is included)
- ovf (OVF format)
- aki/ami/ari (Amazon kernel, ramdisk, or machine image)
Table 1.8. Image Service components
| Component | Description |
|---|---|
|
openstack-glance-api
|
Handles requests and image delivery (interacts with storage back-ends for retrieval and storage). Uses the registry to retrieve image information (the registry service is never, and should never be, accessed directly).
|
|
openstack-glance-registry
|
Manages all metadata associated with each image. Requires a database.
|
|
Database
|
Stores image metadata.
|