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/<repository>:<tag>
• Mirrored image: <your-namespace>/dhi-<repository>:<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 forklift-operator-index image

This Docker Hardened forklift-operator-index image is an Operator Lifecycle Manager (OLM)⁠ File-Based Catalog (FBC) index for the Forklift operator, the upstream project behind Red Hat Migration Toolkit for Virtualization (MTV). It includes:

• opm: The Operator Package Manager CLI (image entrypoint) that manages and serves File-Based Catalog content over gRPC.
• grpc_health_probe: A CLI for probing gRPC health endpoints (for example, Kubernetes/OLM liveness and readiness checks).
• The mtv-fbc⁠ File-Based Catalog for OpenShift v4.22, staged at /configs. The catalog defines the mtv-operator package's release-v2.11 and release-v2.12 channels and their bundles.

The opm serve cache is pre-populated at /tmp/cache at build time, mirroring the upstream catalog.Dockerfile pattern (opm serve /configs --cache-dir=/tmp/cache --cache-only), so the container starts serving immediately without regenerating the cache on every boot.

The default entrypoint is /bin/opm with the default command serve /configs --cache-dir=/tmp/cache, which serves the catalog over gRPC on port 50051. The image also carries the label operators.operatorframework.io.index.configs.v1=/configs so OLM tooling can locate the catalog root.

Run the forklift-operator-index container

Start the catalog index and serve it over gRPC:

$ docker run -d --name forklift-operator-index -p 50051:50051 \
  dhi.io/forklift-operator-index:<tag>

Display opm version information (overrides the default cmd, entrypoint stays /bin/opm):

$ docker run --rm dhi.io/forklift-operator-index:<tag> version

Render the staged catalog to inspect its contents:

$ docker run --rm dhi.io/forklift-operator-index:<tag> render /configs

Check gRPC health from inside a running container:

$ docker exec forklift-operator-index /bin/grpc_health_probe -addr=localhost:50051

Use the index as an OLM CatalogSource

The typical way to consume this image is as the image of an OLM CatalogSource on OpenShift, OKD, or any cluster running the Operator Lifecycle Manager:

apiVersion: operators.coreos.com/v1alpha1
kind: CatalogSource
metadata:
  name: forklift-operator-index
  namespace: openshift-marketplace
spec:
  sourceType: grpc
  image: dhi.io/forklift-operator-index:<tag>
  displayName: Forklift Operator Index
  publisher: Konveyor

$ kubectl apply -f catalogsource.yaml
$ kubectl get catalogsource -n openshift-marketplace forklift-operator-index

Once OLM reports the CatalogSource as READY, the mtv-operator package and its release-v2.11/release-v2.12 channels become available for subscription. Installing the operator itself pulls images from registry.redhat.io/migration-toolkit-virtualization, which may require Red Hat entitlement on the cluster.

Layer your own catalog content

Because runtime images have no shell, extend this image with the exec form of RUN and regenerate the cache with opm rather than a shell script:

FROM dhi.io/forklift-operator-index:<tag>
COPY --chown=65532:65532 my-catalog/ /configs/
RUN ["/bin/opm", "serve", "/configs", "--cache-dir=/tmp/cache", "--cache-only"]

This replaces the shipped mtv-fbc catalog with your own File-Based Catalog while keeping the same entrypoint, labels, and gRPC serving behavior.

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. For example, usage of MD5 fails in FIPS variants.

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.

The following steps outline the general migration process.

1. Find hardened images for your app.

   A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.

2. Update the base image in your Dockerfile.

   Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.

3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile.

   To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.

4. Install additional packages

   Docker Hardened Images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. Inspect the image variants to identify which packages are already installed.

   Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image.

   For Alpine-based images, you can use apk to install packages. For Debian-based images, you can use apt-get to install packages.

Troubleshooting migration

The following are common issues that you may encounter during 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 the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. You may need to copy files to different directories or change permissions so your application running as the 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, even if you map it to a lower port on the host. For example, docker run -p 80:8080 my-image will work because the port inside the container is 8080, and docker run -p 80:81 my-image won't work because the port inside the container is 81.

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

Docker Hardened Images may have different entry points than images such as Docker Official Images. Use docker inspect to inspect entry points for Docker Hardened Images and update your Dockerfile if necessary.