OpenShift Online 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 OpenShift Online registry.
OpenShift Online 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 OpenShift Online about the new image, passing along all the information about it, such as the namespace, name, and image metadata. Different pieces of OpenShift Online react to new images, creating new builds and deployments.
OpenShift Online 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 OpenShift Online registry. In this situation
OpenShift Online will fetch tags from the remote registry upon imagestream
creation. Refreshing the fetched tags is as simple as running
<stream>. When new images are detected, the previously-described build and
deployment reactions occur.
OpenShift Online can communicate with registries to access private image repositories using credentials supplied by the user. This allows OpenShift Online to push and pull images to and from private repositories. The Authentication topic has more information.