Kubernetes Registry and Container Image Registry

Registries are Kubernetes secrets containing credentials used to authenticate with private container registries.

The word “registry” can mean two things, depending on whether it is used to refer to a container or Kubernetes registry:

  • A Container image registry (formerly “Docker registry”) contains container images that you can pull and deploy. The registry is a stateless, scalable server side application that stores and lets you distribute container images.
  • The Kubernetes registry is an image pull secret that your deployment uses to authenticate with an image registry.

Deployments use the Kubernetes registry secret to authenticate with a private image registry and then pull a container image hosted on it.

Currently, deployments pull the private registry credentials automatically only if the workload is created in the Rancher UI and not when it is created via kubectl.

Creating a Registry in Namespaces

Kubernetes Registry and Container Image Registry - 图1Prerequisite:

You must have an available private registry already deployed.

If you need to create a private registry, refer to the documentation pages for your respective runtime:

  1. In the upper left corner, click ☰ > Cluster Management.

  2. Go to the cluster where you want to add a registry and click Explore.

  3. In the left navigation, click either Storage > Secrets or More Resources > Core > Secrets.

  4. Click Create.

  5. Click Registry.

  6. Enter a Name for the registry.

    Kubernetes Registry and Container Image Registry - 图2note

    Kubernetes classifies secrets, certificates, and registries all as secrets, and no two secrets in a project or namespace can have duplicate names. Therefore, to prevent conflicts, your registry must have a unique name among all secrets within your workspace.

  7. Select a namespace for the registry.

  8. Select the website that hosts your private registry. Then enter credentials that authenticate with the registry. For example, if you use Docker Hub, provide your Docker Hub username and password.

  9. Click Save.

Result:

  • Your secret is added to the namespace you chose.
  • You can view the secret in the Rancher UI by clicking either Storage > Secrets or More Resources > Core > Secrets.
  • Any workload that you create in the Rancher UI will have the credentials to access the registry if the workload is within the registry’s scope.

Creating a Registry in Projects

Kubernetes Registry and Container Image Registry - 图3Prerequisites:

You must have an available private registry already deployed.

If you need to create a private registry, refer to the documentation pages for your respective runtime:

Before v2.6, secrets were required to be in a project scope. Projects are no longer required, and you may use the namespace scope instead. As a result, the Rancher UI was updated to reflect this new functionality. However, you may still create a project-scoped registry if desired. Use the following steps to do so:

  1. In the upper left corner, click ☰ > Global Settings in the dropdown.

  2. Click Feature Flags.

  3. Go to the legacy feature flag and click Activate.

  4. In the upper left corner, click ☰ > Cluster Management.

  5. Go to the cluster where you want to add a registry and click Explore.

  6. In the left navigation, click either Storage > Secrets or More Resources > Core > Secrets.

  7. Click Create.

  8. Click Registry.

  9. In the top navigation bar, filter to see only one project.

  10. Enter a Name for the registry.

    Kubernetes Registry and Container Image Registry - 图4note

    Kubernetes classifies secrets, certificates, and registries all as secrets, and no two secrets in a project or namespace can have duplicate names. Therefore, to prevent conflicts, your registry must have a unique name among all secrets within your workspace.

  11. Select a namespace for the registry.

  12. Select the website that hosts your private registry. Then enter credentials that authenticate with the registry. For example, if you use Docker Hub, provide your Docker Hub username and password.

  13. Click Save.

Result:

  • Your secret is added to the individual project you chose.
  • You can view the secret in the Rancher UI by clicking either Storage > Secrets or More Resources > Core > Secrets.
  • Any workload that you create in the Rancher UI will have the credentials to access the registry if the workload is within the registry’s scope.

Kubernetes Registry and Container Image Registry - 图5note

Project-scoped registries on the local cluster are only visible when a single project is selected.

Using a Private Registry

You can deploy a workload with an image from a private registry through the Rancher UI, or with kubectl.

Using the Private Registry with the Rancher UI

To deploy a workload with an image from your private registry,

  1. In the upper left corner, click ☰ > Cluster Management.
  2. Go to the cluster where you want to deploy a workload and click Explore.
  3. Click Workload.
  4. Click Create.
  5. Select the type of workload you want to create.
  6. Enter a unique name for the workload and choose a namespace.
  7. In the Container Image field, enter the URL of the path to the image in your private registry. For example, if your private registry is on Quay.io, you could use quay.io/<Quay profile name>/<Image name>.
  8. Click Create.

Result: Your deployment should launch, authenticate using the private registry credentials you added in the Rancher UI, and pull the container image that you specified.

Using the Private Registry with kubectl

When you create the workload using kubectl, you need to configure the pod so that its YAML has the path to the image in the private registry. You also have to create and reference the registry secret because the pod only automatically gets access to the private registry credentials if it is created in the Rancher UI.

The secret has to be created in the same namespace where the workload gets deployed.

Below is an example pod.yml for a workload that uses an image from a private registry. In this example, the pod uses an image from Quay.io, and the .yml specifies the path to the image. The pod authenticates with the registry using credentials stored in a Kubernetes secret called testquay, which is specified in spec.imagePullSecrets in the name field:

  1. apiVersion: v1
  2. kind: Pod
  3. metadata:
  4.   name: private-reg
  5. spec:
  6.   containers:
  7.   - name: private-reg-container
  8.     image: quay.io/<Quay profile name>/<image name>
  9.   imagePullSecrets:
  10.   - name: testquay

In this example, the secret named testquay is in the default namespace.

You can use kubectl to create the secret with the private registry credentials. This command creates the secret named testquay:

  1. kubectl create secret docker-registry testquay \
  2.     --docker-server=quay.io \
  3.     --docker-username=<Profile name> \
  4.     --docker-password=<password>

To see how the secret is stored in Kubernetes, you can use this command:

  1. kubectl get secret testquay --output="jsonpath={.data.\.dockerconfigjson}" | base64 --decode

The result looks like this:

  1. {"auths":{"quay.io":{"username":"<Profile name>","password":"<password>","auth":"c291bXlhbGo6dGVzdGFiYzEyMw=="}}}

After the workload is deployed, you can check if the image was pulled successfully:

  1. kubectl get events

The result should look like this:

  1. 14s         Normal    Scheduled          Pod    Successfully assigned default/private-reg2 to minikube
  2. 11s         Normal    Pulling            Pod    pulling image "quay.io/<Profile name>/<image name>"
  3. 10s         Normal    Pulled             Pod    Successfully pulled image "quay.io/<Profile name>/<image name>"

For more information, refer to the Kubernetes documentation on creating a pod that uses your secret.