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 ansible-operator image

This Docker Hardened Ansible Operator image is the base image for Kubernetes operators written in Ansible with the Operator SDK⁠.

• ansible-operator: the Operator SDK controller that watches the custom resources listed in watches.yaml and runs the matching Ansible role or playbook on every reconcile
• the Ansible runtime it drives: ansible-core, ansible-runner with the operator's HTTP event plugin, and the kubernetes Python client, installed as a virtual environment under /usr/lib/ansible-operator-runtime with the ansible* and ansible-runner commands on the PATH
• tini as the init process at /tini, the path the upstream entrypoint uses

No Ansible collections are bundled. As upstream does, each operator installs the collections its roles use, usually kubernetes.core and operator_sdk.util, from its own requirements.yml.

Unlike most hardened runtime images, this one ships a POSIX shell and core utilities (dash and coreutils on Debian, busybox on Alpine): Ansible's local connection executes every module through /bin/sh, so the operator cannot run without them.

Build an operator on this image

The Operator SDK scaffolds an Ansible operator as a watches.yaml, a requirements.yml, and roles/ and playbooks/ directories next to a Dockerfile. Point that Dockerfile at this image; nothing else changes:

FROM dhi.io/ansible-operator:<tag>

COPY requirements.yml ${HOME}/requirements.yml
RUN ansible-galaxy collection install -r ${HOME}/requirements.yml \
 && chmod -R ug+rwx ${HOME}/.ansible

COPY watches.yaml ${HOME}/watches.yaml
COPY roles/ ${HOME}/roles/
COPY playbooks/ ${HOME}/playbooks/

HOME is /opt/ansible, the working directory the controller starts in, which is why the default entrypoint finds ./watches.yaml there. The image runs as user 1001 in group 0 like the upstream image, so files copied into ${HOME} are readable by the operator and ansible-galaxy can write the collections under ${HOME}/.ansible.

Build and deploy it with the scaffolded Makefile targets:

make docker-build docker-push IMG=<registry>/<operator>:<version>
make deploy IMG=<registry>/<operator>:<version>

Run the container standalone

The controller is designed to run inside a Kubernetes cluster. Running it standalone only verifies that the image starts:

docker run --rm dhi.io/ansible-operator:<tag>

Without a cluster it logs Failed to get config. because no in-cluster configuration exists, then exits. That is the expected standalone behavior.

To check the controller version:

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

To check the bundled Ansible version:

docker run --rm --entrypoint ansible dhi.io/ansible-operator:<tag> --version

Ports

Environment variables

Non-hardened images vs. Docker Hardened Images

• The controller binary is installed at /usr/bin/ansible-operator; /usr/local/bin/ansible-operator, the path the upstream image and its entrypoint use, is a symlink to it. The same applies to the ansible* and ansible-runner commands, and /tini links to the distribution's tini package (/usr/bin/tini on Debian, /sbin/tini on Alpine).
• The Ansible runtime is a virtual environment under /usr/lib/ansible-operator-runtime instead of the interpreter's global site-packages. PYTHONPATH makes its packages visible to the system interpreter Ansible discovers for its modules, so kubernetes.core modules run unchanged. Overriding PYTHONPATH in a derived image, or pointing ansible_python_interpreter at a different Python minor, drops that path.
• The Debian variants ship only dash and coreutils next to Ansible; the grep, sed, awk, find and tar binaries the upstream UBI base carried are not present there, so shell and command tasks that call them need a dev build stage that installs them. The Alpine variants cover them with busybox applets.
• There is no package manager in the runtime variants, so the common scaffold step USER root, dnf install ..., USER 1001 has no equivalent. Install extra packages in a build stage based on the dev variant and copy the files into the runtime stage, or base the operator on the dev variant when a package manager is acceptable.
• pip, setuptools, wheel, ansible-test and the pip-audit tooling the upstream image leaves behind are not shipped. Install Python packages in a dev build stage and copy the result if an operator needs extra libraries.
• Debian and Alpine variants are published for linux/amd64 and linux/arm64; upstream also publishes ppc64le and s390x.
• The ansible account's home in /etc/passwd is /home/ansible (writable by uid 1001), while HOME and the working directory are /opt/ansible as upstream; ansible_user_dir therefore resolves to /home/ansible, upstream resolves /opt/ansible.
• The image sets LANG, LC_ALL, SSL_CERT_FILE and PYTHONPATH and declares the health and metrics ports; upstream sets neither.
• The FIPS variants cover the controller binary through the Go FIPS module and the Ansible runtime, including the cryptography library, through the system OpenSSL FIPS provider; hashing with MD5 fails in both.
• User 1001:0, HOME and working directory /opt/ansible, the /etc/ansible/ansible.cfg and /etc/ansible/hosts files and the entrypoint stay as upstream.

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

  ansible-operator is an exception: its runtime variants ship /bin/sh and core utilities because Ansible runs its modules through them; they still ship no package manager.

• 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.

ansible-operator is an exception: the runtime variants ship /bin/sh and core utilities because Ansible executes its modules through them. They still ship no package manager.

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.