{product-title} can utilize any server implementing the Docker registry API as a source of images, including the Docker Hub, private registries run by third parties, and the integrated {product-title} registry.
{product-title} provides an integrated container registry called OpenShift Container Registry (OCR) that adds the ability to automatically provision new image repositories on demand. This provides users with a built-in location for their application builds to push the resulting images.
Whenever a new image is pushed to OCR, the registry notifies {product-title} about the new image, passing along all the information about it, such as the namespace, name, and image metadata. Different pieces of {product-title} react to new images, creating new builds and deployments.
OCR can also be deployed as a stand-alone component that acts solely as a container registry, without the build and deployment integration. See Installing a Stand-alone Deployment of OpenShift Container Registry for details.
{product-title} can create containers using images from third party registries,
but it is unlikely that these registries offer the same image notification
support as the integrated {product-title} registry. In this situation
{product-title} will fetch tags from the remote registry upon imagestream
creation. Refreshing the fetched tags is as simple as running oc import-image
<stream>. When new images are detected, the previously-described build and
deployment reactions occur.
{product-title} can communicate with registries to access private image repositories using credentials supplied by the user. This allows {product-title} to push and pull images to and from private repositories. The Authentication topic has more information.