Registry

The default registry is Docker Hub, but you can change it using registry/server.

Using a local container registry

If the registry server starts with localhost, Kamal will start a local Docker registry on that port and push the app image to it.

registry:
  server: localhost:5555

Using Docker Hub as the container registry

By default, Docker Hub creates public repositories. To avoid making your images public, set up a private repository before deploying, or change the default repository privacy settings to private in your Docker Hub settings.

A reference to a secret (in this case, KAMAL_REGISTRY_PASSWORD) will look up the secret in the local environment:

registry:
  username:
    - <your docker hub username>
  password:
    - KAMAL_REGISTRY_PASSWORD

Using AWS ECR as the container registry

You will need to have the AWS CLI installed locally for this to work. AWS ECR’s access token is only valid for 12 hours. In order to avoid having to manually regenerate the token every time, you can use ERB in the deploy.yml file to shell out to the AWS CLI command and obtain the token:

registry:
  server: <your aws account id>.dkr.ecr.<your aws region id>.amazonaws.com
  username: AWS
  password: <%= %x(aws ecr get-login-password) %>

Using GCP Artifact Registry as the container registry

To sign into Artifact Registry, you need to create a service account and set up roles and permissions. Normally, assigning the roles/artifactregistry.writer role should be sufficient.

Once the service account is ready, you need to generate and download a JSON key and base64 encode it:

base64 -i /path/to/key.json | tr -d "\\n"

You’ll then need to set the KAMAL_REGISTRY_PASSWORD secret to that value.

Use the environment variable as the password along with _json_key_base64 as the username. Here’s the final configuration:

registry:
  server: <your registry region>-docker.pkg.dev
  username: _json_key_base64
  password:
    - KAMAL_REGISTRY_PASSWORD

Validating the configuration

You can validate the configuration by running:

kamal registry login