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 Hubble Proto Hardened image

This hardened image provides Protocol Buffer compiler plugins used to generate Go code from proto definitions. The image packages three Go protoc plugins that are compatible with Cilium Hubble's proto definitions.

Included tools in this image:

• protoc-gen-go - Protocol buffer compiler plugin for Go (generates message code)
• protoc-gen-go-grpc - Protocol buffer compiler plugin for Go gRPC (generates service code)
• protoc-gen-go-json - Protocol buffer compiler plugin for JSON marshaling (maintained fork by mfridman)

Plugin versions are pinned to match those used in upstream Cilium's build tooling, ensuring compatibility with Hubble's proto definitions.

The image layout places these binaries under /usr/bin/hubble-proto/, suitable for use in multi-stage builds or as a tooling container during CI.

Usage examples

Example: Check versions of the included plugins

docker run --rm dhi.io/hubble-proto:<tag> /usr/bin/hubble-proto/protoc-gen-go --version
docker run --rm dhi.io/hubble-proto:<tag> /usr/bin/hubble-proto/protoc-gen-go-grpc --version
docker run --rm dhi.io/hubble-proto:<tag> /usr/bin/hubble-proto/protoc-gen-go-json --version

Note: This image contains only the protoc plugins, not protoc itself. You need to install protoc separately or use it from another image.

Common Hubble Proto use cases

• CI/CD pipelines: Use this image to generate Go code from proto definitions during builds
• Multi-stage Docker builds: Copy plugins into build stages that have protoc installed
• Consistent tooling: Pin plugin versions to ensure deterministic generated code across environments

Non-hardened images vs Docker Hardened Images

Key differences

Hardened image debugging

Docker Hardened Images for tooling containers like Hubble Proto do not include a shell or package manager by default. Since this image only provides static binaries (protoc plugins), debugging typically involves verifying the plugin versions and testing their functionality.

For debugging issues with the protoc plugins themselves, you can use Docker Debug to attach to a running container:

docker debug <container-name>

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

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.

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.