Private Docker Registry

The docker-registry charm deploys a local image registry for your cluster, taking care of the storage and distribution of container images. There are a few reasons why this may be a useful option for your cluster:

• Providing the images required by Charmed Kubernetes without requiring access to a public registry (e.g. in environments where network access is controlled, expensive or otherwise problematic).
• Providing images required by workloads running on the cluster.

When deployed and related to the cluster as described below, this registry will be checked first for any image requests, so it can be used in addition to public registries. For more details of the mechanics of the Docker Registry, see the upstream documentation at https://docs.docker.com/registry.

Deploying

The registry is deployed as a stand-alone application. Many deployment scenarios are described in the charm readme. The most common scenario for Kubernetes integration is to configure a registry with TLS and basic (htpasswd) authentication enabled.

If needed, consult the quickstart guide to install Charmed Kubernetes. Then deploy and configure docker-registry as follows.

juju deploy cs:~containers/docker-registry
juju add-relation docker-registry easyrsa:client
juju config docker-registry \
  auth-basic-user='admin' \
  auth-basic-password='password'

Custom Certificates

Relating docker-registry to easyrsa above will generate new TLS data to support secure communication with the registry. Alternatively, custom TLS data may be provided as base64-encoded config options to the charm:

juju config docker-registry \
  tls-ca-blob=$(base64 /path/to/ca) \
  tls-cert-blob=$(base64 /path/to/cert) \
  tls-key-blob=$(base64 /path/to/key)

Proxied Registry

Advanced networking or highly available deployment scenarios may require multiple docker-registry units to be deployed behind a proxy. In this case, the network information of the proxy will be shared with the container runtime units when the registry is related.

The environment described in the Deploy section above can be adjusted to create a highly available registry as follows:

juju deploy haproxy
juju add-unit docker-registry
juju remove-relation docker-registry easyrsa:client
juju add-relation docker-registry haproxy:reverseproxy

Verify

Make note of the registry address. By default, this address is only accessible within the deployment model. See the charm readme for host and proxy configuration options if desired.

export IP=`juju run --unit docker-registry/0 'network-get website --ingress-address'`
export PORT=`juju config docker-registry registry-port`
export REGISTRY=$IP:$PORT

Verify basic authentication is working:

juju run --unit docker-registry/0 "docker login -u admin -p password $REGISTRY"
Login Succeeded
...

Connecting to a Charmed Kubernetes cluster

Relate the deployed registry to the appropriate container runtime for your cluster. This configures the runtime with authentication, proxy, and/or TLS data from the registry, and allows your registry to be used by the cluster to pull images for pods.

Containerd

juju add-relation docker-registry containerd

Docker

juju add-relation docker-registry docker

Kubernetes images

A list of images that may be used by Charmed Kubernetes can be found in the container-images.txt document. This is a comprehensive list sorted by release; not all images are required for all deployments. Take note of the images required by your deployment that will need to be hosted in your private registry. A list of images required by a specific release is also included on the ‘components’ page in the documentation, for example, the list for the 1.20 release is located on the 1.20 components page

Hosting images

To make an image available in the deployed registry, it must be tagged and pushed. As an example, push the defaultbackend-amd64 image to docker-registry:

juju run-action docker-registry/0 \
  push \
  image=k8s.gcr.io/defaultbackend-amd64:1.5 \
  tag=$REGISTRY/defaultbackend-amd64:1.5 \
  --wait
...
  results:
    outcome: success
    raw: pushed 172.31.28.74:5000/k8s.gcr.io/defaultbackend-amd64:1.5
  status: completed
...

The above procedure should be repeated for all required images.

Using the registry for cluster components

The image registry used by Charmed Kubernetes for images used in managing or supporting components of the cluster itself is controlled by a kubernetes-master config option. Configure kubernetes-master to use your private registry as follows:

juju config kubernetes-master image-registry=$REGISTRY