Overview

OKD 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 OKD registry.

Integrated OKD Registry

OKD provides an integrated container registry that adds the ability to provision new image repositories on the fly. This allows users to automatically have a place for their builds to push the resulting images.

Whenever a new image is pushed to the integrated registry, the registry notifies OKD about the new image, passing along all the information about it, such as the namespace, name, and image metadata. Different pieces of OpenShift react to new images, creating new builds and deployments.

Third Party Registries

OKD 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 OKD registry. In this situation OKD 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.

Authentication

OKD can communicate with registries to access private image repositories using credentials supplied by the user. This allows OpenShift to push and pull images to and from private repositories. The Authentication topic has more information.