<strong>registry</strong> overview | <strong>registry</strong>

Glossary of common terms for OpenShift image registry
Integrated OpenShift image registry
Automatically pruning images
Creating containers by using images from third-party registries
Red Hat Quay registries
Authentication enabled Red Hat registry

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

Glossary of common terms for OpenShift image registry

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 OKD 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 OKD clusters.
OpenShift image registry: OpenShift image registry is the registry provided by OKD 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 OKD 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.

Integrated OpenShift image registry

OKD 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.

Additional resources

Image registry Operator in OKD

Automatically pruning images

Images from the OpenShift image registry that are no longer required by the system because of age, status, or exceed limits being automatically pruned. As a cluster administrator, can configure or suspend the pruning Custom Resource (CR).

Prerequisites

You have access to an OKD cluster using an account with cluster administrator permissions.
Install the oc CLI.

The behavior of the Image registry Operator for managing the pruner is independent to the managementState specified on the ClusterOperator object of the Image registry Operator. If the Image registry Operator is not in the Managed state, the image pruner can still be configured and managed by the Pruning Custom Resource.

However, the managementState of the Image registry Operator alters the behavior of the deployed image pruner job:

Managed: the --prune-registry flag for the image pruner is set to true.
Removed: the --prune-registry flag for the image pruner is set to false, meaning it only prunes image metadata in etcd.

Procedure

Verify that the object named imagepruners.imageregistry.operator.openshift.io/cluster contains the following spec and status fields:

spec:
  schedule: 0 0 * * *
  suspend: false
  keepTagRevisions: 3
  keepYoungerThanDuration: 60m
  keepYoungerThan: 3600000000000
  resources: {}
  affinity: {}
  nodeSelector: {}
  tolerations: []
  successfulJobsHistoryLimit: 3
  failedJobsHistoryLimit: 3
status:
  observedGeneration: 2
  conditions:
  - type: Available
    status: "True"
    lastTransitionTime: 2019-10-09T03:13:45
    reason: Ready
    message: "Periodic image pruner has been created."
  - type: Scheduled
    status: "True"
    lastTransitionTime: 2019-10-09T03:13:45
    reason: Scheduled
    message: "Image pruner job has been scheduled."
  - type: Failed
    staus: "False"
    lastTransitionTime: 2019-10-09T03:13:45
    reason: Succeeded
    message: "Most recent image pruning job succeeded."

schedule: CronJob formatted schedule. This is an optional field, default is daily at midnight.
suspend: If set to true, the CronJob running pruning is suspended. This is an optional field, default is false. The initial value on new clusters is false.
keepTagRevisions: The number of revisions per tag to keep. This is an optional field, default is 3. The initial value is 3.
keepYoungerThanDuration: Retain images younger than this duration. This is an optional field. If a value is not specified, either keepYoungerThan or the default value 60m (60 minutes) is used.
keepYoungerThan: Deprecated. The same as keepYoungerThanDuration, but the duration is specified as an integer in nanoseconds. This is an optional field. When keepYoungerThanDuration is set, this field is ignored.
resources: Standard pod resource requests and limits. This is an optional field.
affinity: Standard pod affinity. This is an optional field.
nodeSelector: Standard pod node selector. This is an optional field.
tolerations: Standard pod tolerations. This is an optional field.
successfulJobsHistoryLimit: The maximum number of successful jobs to retain. Must be greater than or equal to 1 to ensure metrics are reported. This is an optional field, default is 3. The initial value is 3.
failedJobsHistoryLimit: The maximum number of failed jobs to retain. Must be greater than or equal 1 to ensure metrics are reported. This is an optional field, default is 3. The initial value is 3.
observedGeneration: The generation observed by the Operator.
conditions: The standard condition objects with the following types:
- Available: Indicates if the pruning job has been created. Reasons can be Ready or Error.
- Scheduled: Indicates if the next pruning job has been scheduled. Reasons can be Scheduled, Suspended, or Error.
- Failed: Indicates if the most recent pruning job failed.

Creating containers by using images from third-party registries

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.

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

OKD 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, OKD 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

Use the Red Hat Ecosystem Catalog to search for specific container images from the Red Hat Repository and select the required image.
Click Get this image to find the command for your container image.
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
```
```
 Username:<your_registry_account_username>
 Password:<your_registry_account_password>
```
Download the image and save it locally by running the following command:
```
$ podman pull registry.redhat.io/<repository_name>
```

Red Hat Quay registries

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 OKD, similar to any remote container image registry.

Additional resources

Red Hat Quay product documentation

Authentication enabled Red Hat registry

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 OKD.

OKD 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 OKD, Red Hat does not support the method for production deployments. Restrict this authentication method to standalone projects outside OKD.

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.

Additional resources

registry service accounts

OpenShift image registry overview

Glossary of common terms for OpenShift image registry

Integrated OpenShift image registry

Automatically pruning images

Creating containers by using images from third-party registries

Red Hat Quay registries

Authentication enabled Red Hat registry