How to use this image

Before you can use any Docker Hardened Image, you must mirror the image repository from the catalog to your organization. To mirror the repository, select either Mirror to repository or View in repository > Mirror to repository, and then follow the on-screen instructions.

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.

Deploy Calico Pod2Daemon FlexVol in Kubernetes

First follow the authentication instructions for DHI in Kubernetes⁠.

Calico Pod2Daemon FlexVol runs as an init container on Calico node pods. The Tigera Operator deploys and manages it as part of a full Calico stack. This image is not a standalone application and is intended to run alongside other Calico components.

Replace <your-namespace> with your organization's namespace, <secret name> with your Kubernetes image pull secret, and <tag> with the image variant you want to use.

The Tigera Operator manages all Calico components. To use hardened images, configure the Installation custom resource with your DHI registry settings (registry, imagePath, and imagePrefix). See the Calico Kube Controllers guides⁠ for the same Installation CR pattern and Helm install steps; they apply to Pod2Daemon FlexVol and every other Calico component image.

Note: If you only have the Calico Pod2Daemon FlexVol DHI image available, other Calico components may fail to start with ImagePullBackOff until their DHI images are also mirrored.

Image variants

Docker Hardened Images come in different variants depending on their intended use.

• 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 the 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 variant 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.

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.

When deploying with the Tigera Operator, configure the Installation CR so the operator pulls dhi/calico-pod2daemon-flexvol (and other Calico DHI images) instead of upstream quay.io/calico/* references. See Calico Kube Controllers guides⁠ for the Installation CR fields.

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.