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Chapter 1. OpenShift image registry overview

OpenShift Container Platform can build images from your source code, deploy them, and manage their lifecycle. OpenShift Container Platform provides an internal, integrated container image registry that can be deployed in your OpenShift Container Platform environment to locally manage images. The overview section includes OpenShift image registry reference information and links for registries commonly used with OpenShift Container Platform.

This glossary defines the common terms that are used in the registry content.

container
Lightweight and executable images that consist of software and all its dependencies. Because containers virtualize the operating system, you can run containers in a data center, a public or private cloud, or your local host.
image repository
An image repository is a collection of related container images and tags identifying images.
mirror registry
The mirror registry is a registry that holds the mirror of OpenShift Container Platform images.
namespace
A namespace isolates groups of resources within a single cluster.
pod
The pod is the smallest logical unit in Kubernetes. A pod consists of one or more containers to run in a compute node.
private registry
A registry is a server that implements the container image registry API. A private registry is a registry that requires authentication so that users can access the content of the registry.
public registry
A registry is a server that implements the container image registry API. A public registry is a registry that serves its content publicly.
Quay.io
A public Red Hat Quay Container Registry instance provided and maintained by Red Hat, which serves most of the container images and Operators to OpenShift Container Platform clusters.
OpenShift image registry
OpenShift image registry is the registry provided by OpenShift Container Platform to manage images.
registry authentication
To push and pull images to and from private image repositories, the registry needs to authenticate its users with credentials.
route
Exposes a service to allow for network access to pods from users and applications outside the OpenShift Container Platform instance.
scale down
To decrease the number of replicas.
scale up
To increase the number of replicas.
service
A service exposes a running application on a set of pods.

1.2. Integrated OpenShift image registry
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OpenShift Container Platform provides a built-in container image registry that runs as a standard workload on the cluster. The registry is configured and managed by an infrastructure Operator. The registry provides an out-of-the-box solution that runs on top of existing cluster infrastructure, so that you can manage the images that run workloads.

You can scale the registry up or down like any other cluster workload and the registry does not require specific infrastructure provisioning. The registry also integrates into the cluster user authentication and authorization system, which means that defining user permissions on image resources controls access to create and retrieve images.

The registry is typically used as a publication target for images built on the cluster and as a source of images for workloads running on the cluster. When you push a new image to the registry, a notification gets sent to the cluster of the new image so that other components can react to and consume the updated image.

Image data is stored in two locations. The actual image data is stored in a configurable storage location, such as cloud storage or a filesystem volume. The image metadata, which is exposed by the standard cluster APIs and is used to perform access control, is stored as standard API resources, specifically images and image streams.

Some container image registries require access authorization. Podman is an open source tool for managing containers and container images and interacting with image registries. You can use Podman to authenticate your credentials, pull the registry image, and store local images in a local file system. The procedure provides a generic example of authenticating the registry with Podman.

OpenShift Container Platform can communicate with registries to access private image repositories by using credentials supplied by the user. This allows OpenShift Container Platform to push and pull images to and from private repositories.

OpenShift Container Platform can create containers by using images from third-party registries, but these registries unlikely offer the same image notification support as the integrated OpenShift image registry.In this situation, OpenShift Container Platform fetches tags from the remote registry upon image stream creation. To refresh the fetched tags, run oc import-image <stream>. When new images are detected, the previously described build and deployment reactions occur.

Procedure

  1. Use the Red Hat Ecosystem Catalog to search for specific container images from the Red Hat Repository and select the required image.
  2. Click Get this image to find the command for your container image.

  3. Log in by running the following command and entering your username and password to authenticate. Example output is shown for demonstrative purposes. 

    $ podman login registry.redhat.io
    Copy to Clipboard Toggle word wrap 
     Username:<your_registry_account_username>
 Password:<your_registry_account_password>
    Copy to Clipboard Toggle word wrap

  4. Download the image and save it locally by running the following command: 

    $ podman pull registry.redhat.io/<repository_name>
    Copy to Clipboard Toggle word wrap

1.4. Red Hat Quay registries
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If you need an enterprise-quality container image registry, Red Hat Quay is available both as a hosted service and as software that you can install in your own data center or cloud environment. Advanced features in Red Hat Quay include geo-replication, image scanning, and the ability to roll back images.

Visit the Quay.io site to set up your own hosted Quay registry account. After that, follow the Quay Tutorial to log in to the Quay registry and start managing your images.

You can access your Red Hat Quay registry from OpenShift Container Platform, similar to any remote container image registry.

1.5. Authentication enabled Red Hat registry
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All container images available through the Container images section of the Red Hat Ecosystem Catalog are hosted on an image registry, registry.redhat.io. The registry, registry.redhat.io, requires authentication for access to images and hosted content on OpenShift Container Platform.

Note

OpenShift Container Platform pulls images from registry.redhat.io, so you must configure your cluster to use it.

The new registry uses standard OAuth mechanisms for authentication, with the following methods:

  • Authentication token. Tokens, which are generated by administrators, are service accounts that give systems the ability to authenticate against the container image registry. Service accounts are not affected by changes in user accounts, so the token authentication method is reliable and resilient. This is the only supported authentication option for production clusters.
  • Web username and password. This is the standard set of credentials you use to log in to resources such as access.redhat.com. While you could use this authentication method with OpenShift Container Platform, Red Hat does not support the method for production deployments. Restrict this authentication method to standalone projects outside OpenShift Container Platform.

You can use podman login with your credentials, either username and password or authentication token, to access content on the new registry.

All image streams point to the new registry, which uses the installation pull secret to authenticate.

You must place your credentials in either of the following places:

  • openshift namespace. Your credentials must exist in the openshift namespace so that the image streams in the openshift namespace can import.
  • Your host. Your credentials must exist on your host because Kubernetes uses the credentials from your host when it goes to pull images.
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