Skip to main content

Glance

Glance is the OpenStack image service (infrastructure virtualization) that provides discovery, registration, storage, and delivery of Virtual Machine (VM) and container disk images for cloud environments.

  • Image registry and metadata catalog for disk images (infrastructure virtualization)
  • Pluggable back-end storage for images, including object and file stores (storage integration)
  • Image discovery, upload, download, and sharing via RESTful APIs (cloud infrastructure services)
  • Format-agnostic handling of VM and container images (image management)
  • Integration with other OpenStack services for provisioning and lifecycle workflows (cloud platform integration)

More About Glance

Glance is the image management component of the OpenStack cloud platform, focused on providing a centralized service for discovery, registration, and delivery of VM and container disk images (infrastructure virtualization). It addresses the problem of consistently managing image assets across large-scale, multi-tenant cloud deployments, where compute nodes and orchestration layers depend on a reliable source of bootable images and associated metadata.

At its core, Glance exposes a RESTful Application Programming Interface (API) (cloud infrastructure services) that allows clients and other OpenStack services to upload, discover, update, and retrieve images. Images are stored along with metadata such as disk format, container format, size, checksums, and custom properties, which enable filtering, policy enforcement, and integration with scheduling and orchestration components. Glance functions as both an image registry (metadata catalog) and, via back ends, an image repository, depending on deployment choices.

Glance supports a pluggable storage architecture (storage integration), allowing operators to configure different back ends for image data. Common options include object storage systems and file-based stores, configured through drivers and back-end settings. This design enables cloud operators to align image storage with existing infrastructure choices, data durability requirements, and performance characteristics without changing the API surface exposed to clients.

In enterprise and institutional environments, Glance is typically deployed alongside other OpenStack services such as Compute (Nova) and Identity (Keystone) as part of an Infrastructure-as-a-Service (IaaS) cloud (cloud platform integration). Nova uses Glance to locate and retrieve images when instantiating VM instances, while Keystone provides authentication and authorization for image operations across tenants. Glance supports multi-tenant access controls, image visibility settings (public, private, shared), and image versioning behavior as described in its documentation, which together support governance and operational policies.

From an architectural perspective, Glance can be deployed in a distributed manner, with API services, registry components where used, and storage back ends scaled according to demand (cloud infrastructure architecture). Operators can configure image caching on compute nodes or intermediate proxies to optimize retrieval. The service integrates with messaging, configuration, and logging frameworks standard across OpenStack, supporting operational monitoring and lifecycle management.

For directory and taxonomy purposes, Glance fits into the category of cloud image management and registry (infrastructure virtualization and cloud infrastructure services). It provides a programmable interface for image lifecycle operations, a metadata catalog for image discovery and policy-driven selection, and extensible storage integration for diverse back ends. Within OpenStack deployments, it functions as the canonical source of bootable image artifacts used by compute, orchestration, and provisioning workflows.