How to use this image

All examples in this guide use the public image. If you've mirrored the repository for your own use (for example, to your Docker Hub namespace), update your commands to reference the mirrored image instead of the public one.

For example:

• Public image: dhi.io/registration-operator:<tag>
• Mirrored image: <your-namespace>/dhi-registration-operator:<tag>

For the examples, you must first use docker login dhi.io to authenticate to the registry to pull the images.

What's included in this registration-operator image

This Docker Hardened registration-operator image is a component of the Open Cluster Management (OCM)⁠ project.

• The registration-operator binary built from the official OCM releases
• Symlink at /registration-operator for OCM cluster-manager argv compatibility
• Default command [/usr/local/bin/registration-operator, hub] for the hub operator deployment
• Configuration via command-line flags

The registration-operator provides two operators:

• Cluster Manager (hub subcommand) — installs OCM foundational components on the hub cluster
• Klusterlet (klusterlet subcommand) — installs agent components on managed clusters

It is designed to run within a Kubernetes cluster to manage multi-cluster operations.

Run the registration-operator container

The registration-operator is designed to run within a Kubernetes cluster. Running it standalone requires Kubernetes API access and proper configuration.

To display version information:

docker run --rm dhi.io/registration-operator:<tag> /usr/local/bin/registration-operator --version

To display help information:

docker run --rm dhi.io/registration-operator:<tag> /usr/local/bin/registration-operator --help

Deploy in Kubernetes

The recommended way to deploy registration-operator is using the OCM Helm chart or the clusteradm CLI.

For detailed deployment instructions, configuration options, and integration guides, refer to the official documentation at https://open-cluster-management.io/⁠

Non-hardened images vs Docker Hardened Images

Docker Hardened Images prioritize security through minimalism. Runtime images don't contain a shell or package manager to reduce attack surface. For debugging, use Docker Debug⁠ to attach to containers with ephemeral debugging tools.

Image variants

Docker Hardened Images come in different variants depending on their intended use. Image variants are identified by their tag.

• Runtime variants are designed to run your application in production. These images are intended to be used either directly or as the FROM image in the final stage of a multi-stage build. These images typically:

  • Run as a nonroot user
  • Do not include a shell or a package manager
  • Contain only the minimal set of libraries needed to run the app

• Build-time variants typically include dev in the tag name and are intended for use in the first stage of a multi-stage Dockerfile. These images typically:

  • Run as the root user
  • Include a shell and package manager
  • Are used to build or compile applications

• FIPS variants include fips in the variant name and tag. They come in both runtime and build-time variants. These variants use cryptographic modules that have been validated under FIPS 140, a U.S. government standard for secure cryptographic operations. Note: this image uses FIPS lenient mode (fips140=on) because the upstream openshift/library-go dependency uses MD5 for resource caching and SHA-1 for certificate generation. These are non-security uses that cannot be patched without forking the dependency.

To view the image variants and get more information about them, select the Tags tab for this repository, and then select a tag.

Migrate to a Docker Hardened Image

To migrate your application to a Docker Hardened Image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Docker Hardened Image. This and a few other common changes are listed in the following table of migration notes.

Troubleshooting migration

General debugging

The hardened images intended for runtime don't contain a shell nor any tools for debugging. The recommended method for debugging applications built with Docker Hardened Images is to use Docker Debug⁠ to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

Permissions

By default image variants intended for runtime, run as a nonroot user. Ensure that necessary files and directories are accessible to that user. You may need to copy files to different directories or change permissions so your application running as a nonroot user can access them.

Privileged ports

Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10. To avoid issues, configure your application to listen on port 1025 or higher inside the container.

No shell

By default, image variants intended for runtime don't contain a shell. Use dev images in build stages to run shell commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers with no shell.

Entry point

The upstream quay.io/open-cluster-management/registration-operator image does not configure an entrypoint and places the binary at /registration-operator. The Docker Hardened image runs /usr/local/bin/registration-operator directly. If your existing Dockerfile, Compose file, or Kubernetes manifests override command or args, inspect and update those settings to match the Docker Hardened image layout.