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/kubeflow-notebook-controller:<tag>
• Mirrored image: <your-namespace>/dhi-kubeflow-notebook-controller:<tag>

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

Start a Kubeflow Notebook Controller image

The controller runs as a controller-manager. The entrypoint is /manager, the image has no default command, and the working directory is /. The controller needs a Kubernetes cluster with the Notebook CRD and RBAC rules before it can reconcile anything, so the local check below prints the available flags with --help:

docker run --rm dhi.io/kubeflow-notebook-controller:<tag> --help

Replace <tag> with a published tag, such as 1.11.1-debian13 or 1.11.1-alpine3.24.

Run in Kubernetes

The following overlay uses the upstream config/default kustomization at the v1.11.1 tag. It installs the notebooks.kubeflow.org CRD, the RBAC rules for StatefulSets, Services, and Notebooks, and the controller Deployment in the notebook-controller-system namespace. The overlay replaces the upstream controller image with this image, and runs the controller as uid and gid 65532, the image's numeric user and group:

# kustomization.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - github.com/kubeflow/notebooks/components/notebook-controller/config/default?ref=v1.11.1
images:
  - name: ghcr.io/kubeflow/notebooks/notebook-controller
    newName: dhi.io/kubeflow-notebook-controller
    newTag: 1.11.1-debian13
configMapGenerator:
  - name: config
    behavior: merge
    literals:
      - USE_ISTIO=false
patches:
  - target:
      kind: Deployment
      name: notebook-controller-deployment
    patch: |-
      - op: replace
        path: /spec/template/spec/containers/0/securityContext/runAsUser
        value: 65532
      - op: add
        path: /spec/template/spec/containers/0/securityContext/runAsGroup
        value: 65532

Apply it with:

kubectl apply -k .

Your cluster must be able to pull from dhi.io, for example through an image pull secret.

The upstream Deployment sets runAsUser: 1000 and no group. This image runs as uid and gid 65532, so the overlay sets both to 65532 and keeps the upstream runAsNonRoot: true. For build steps and the full deployment flow, see the upstream component README⁠.

The upstream config/default sets USE_ISTIO=true, so the controller reconciles Istio VirtualService objects. The configMapGenerator in the overlay sets USE_ISTIO=false, so this example starts on a cluster without Istio. On a cluster that runs Istio, set it to true. Turn on culling and set Istio⁠ shows the same setting alongside culling.

Common use cases

Run with leader election

Leader election ensures that only one controller manager is active at a time. Enable it if you run more than one replica. Add these entries to the patches list of the overlay from the previous section:

- target:
    kind: Deployment
    name: notebook-controller-deployment
  patch: |-
    - op: add
      path: /spec/template/spec/containers/0/args
      value: ["--enable-leader-election"]
- target:
    kind: Role
    name: notebook-controller-leader-election-role
  patch: |-
    - op: add
      path: /rules/-
      value:
        apiGroups:
          - coordination.k8s.io
        resources:
          - leases
        verbs:
          - get
          - create
          - update

The upstream leader-election Role grants permissions on ConfigMaps and Events only. The controller takes its leader-election lock on a Lease as well, so the second entry grants the Lease permissions. Without it, the manager repeatedly fails Lease get and create with forbidden, never becomes leader, and does not reconcile Notebooks.

Turn on culling and set Istio

The upstream manifests read their runtime settings from a ConfigMap named config. The upstream defaults are in params.env⁠: USE_ISTIO=true, ENABLE_CULLING=false, CULL_IDLE_TIME=1440, and IDLENESS_CHECK_PERIOD=1. This overlay turns on culling and sets Istio usage explicitly. Set USE_ISTIO to match whether your cluster runs Istio. Replace the configMapGenerator from the first example with this one, so the config ConfigMap has a single entry:

configMapGenerator:
  - name: config
    behavior: merge
    literals:
      - ENABLE_CULLING=true
      - USE_ISTIO=false

Non-hardened images vs. Docker Hardened Images

• Ports. The image declares 8080/tcp (metrics) and 8081/tcp (health probes). The upstream image does not declare them, but the controller listens on both by default (--metrics-addr=:8080 and --probe-addr=:8081).
• Entrypoint path. The controller binary is at /usr/bin/manager, and /manager is a symlink to it. The entrypoint path matches the upstream image, so manifests that run /manager keep working.
• User. The runtime image runs as nonroot (uid and gid 65532), the same user as the upstream image. The upstream Deployment manifest sets uid 1000 instead. The Kubernetes example in Run in Kubernetes⁠ sets uid and gid 65532 to match the image.
• Shell and package manager. Runtime images include neither. The dev variants run as root and include a shell and a package manager.

FIPS variants

The -fips and -fips-dev tags, such as 1.11.1-debian13-fips and 1.11.1-alpine3.24-fips, are FIPS builds. They use the Go FIPS 140-3 module and an OpenSSL FIPS provider on the operating system. The image metadata declares fips-compliant: true and stig-certified: true. Use these tags when your environment requires FIPS-compliant builds.

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.