Docker Registry (Optional)

The section describes how to install an insecure docker registry in Kubernetes, using the standard Kubernetes helm charts.

A local docker registry can be used to push container images directly to the cluster, which could be useful for example in the following cases:

• The CORD POD has no Internet access, so container images cannot be downloaded directly from DockerHub to the POD.

• You are developing new CORD components, or modifying existing ones. You may want to test your changes before uploading the image to the official docker repository. In this case, your workflow might be to build your new container and push it to the local registry.

More informations about docker registries can be found at https://docs.docker.com/registry/.

Note: Insecure registries can be used for development, POCs or lab trials. You should not use this in production. There are planty of documents online that guide you through secure registry setup.

Deploy a Registry Using Helm

Helm provides a default helm chart to deploy an insecure registry on your Kubernetes cluster. The following command deploys the registry and exposes the port 30500. (You may want to change it with any value that fit your deployment needs.)

helm install stable/docker-registry --set service.nodePort=30500,service.type=NodePort -n docker-registry

The registry can be queried at any time, for example:

curl -X GET http://KUBERNETES_IP:30500/v2/_catalog

Tag and Push Images to the Docker Registry

For the images to be consumed on the Kubernetes cluster, they need to be first tagged, and pushed to the local registry:

Supposing your docker-registry address is:

192.168.0.1:30500

and that your original image name is called:

xosproject/vsg-synchronizer

you'll need to tag the image as

192.168.0.1:30500/xosproject/vsg-synchronizer

For example, you can use the docker tag command to do this:

docker tag xosproject/vsg-synchronizer:candidate 192.168.0.1:30500/xosproject/vsg-synchronizer:candidate

Now, you can push the image to the registry. For example, with docker push:

docker push 192.168.0.1:30500/xosproject/vsg-synchronizer:candidate

The image should now be in the local docker registry on your cluster.

Use the tag-and-push Script

Sometimes you may need to download, tag and push lots of images. This can become a long and error prone operation if done manually. For this reason, we provide an optional tool that automates the tag and push procedures. The script can be found here.

Modify the Helm Charts to Use Your Images

Now that your custom images are in the local docker registry on the Kubernetes cluster, you can modify the CORD helm charts to instruct the system to consume them instead of using the default images from DockerHub.

Image names and tags are specified in the values.yaml file of each chart (look in the main chart directory), or alternatively, in the configuration files in the config directory.

Simply modify the values as needed, uninstall the containers previously deployed, and deploy them again.

Note: It is better to extend the existing helm charts, rather than directly modifying them. This way you can keep the original configuration as it is, and just override some values when needed. You can do this by writing your additional configuration yaml file, and parsing it as needed, adding -f my-additional-config.yml to your helm commands.

The full CORD helm charts reference documentation is available here.