Image service overview

Image service overview

The OpenStack Image service is central to Infrastructure-as-a-Service (IaaS) as shown in Conceptual architecture. It accepts API requests for disk or server images, and metadata definitions from end users or OpenStack Compute components. It also supports the storage of disk or server images on various repository types, including OpenStack Object Storage.

A number of periodic processes run on the OpenStack Image service to support caching. Replication services ensure consistency and availability through the cluster. Other periodic processes include auditors, updaters, and reapers.

The OpenStack Image service includes the following components:

Accepts Image API calls for image discovery, retrieval, and storage.

Stores, processes, and retrieves metadata about images. Metadata includes items such as size and type.


The registry is a private internal service meant for use by OpenStack Image service. Do not expose this service to users.

Stores image metadata and you can choose your database depending on your preference. Most deployments use MySQL or SQLite.
Storage repository for image files
Various repository types are supported including normal file systems (or any filesystem mounted on the glance-api controller node), Object Storage, RADOS block devices, VMware datastore, and HTTP. Note that some repositories will only support read-only usage.
Metadata definition service
A common API for vendors, admins, services, and users to meaningfully define their own custom metadata. This metadata can be used on different types of resources like images, artifacts, volumes, flavors, and aggregates. A definition includes the new property’s key, description, constraints, and the resource types which it can be associated with.
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