actions runner controller

Run the Actions Runner Controller container

Actions Runner Controller is designed to run inside a Kubernetes cluster and requires in-cluster configuration, Kubernetes RBAC, and a GitHub credential (GitHub App or PAT). It is not intended to be used as a standalone docker run process for production workloads.

To verify the image is accessible and list the controller's supported flags, run:

docker run --rm --entrypoint /usr/local/bin/manager registry.ghost-prod.alphabravo.io/ghost-base/gha-runner-scale-set-controller:<tag> --help

The manager binary does not implement a dedicated --version flag; its build metadata is embedded via Go's ldflags and is logged at runtime once the controller connects to the Kubernetes API server. Outside a cluster, the manager logs its options and exits with an error (it cannot authenticate without a valid GitHub credential), which is expected.

Deploy Actions Runner Controller in Kubernetes

The recommended deployment method is the official Helm charts. ARC uses two charts: one for the controller (gha-runner-scale-set-controller) and one for each runner scale set (gha-runner-scale-set). Both are published as OCI charts under oci://ghcr.io/actions/actions-runner-controller-charts/.

1. Install the controller chart with the Docker Hardened image:

helm install arc \
  --namespace arc-systems \
  --create-namespace \
  --set image.repository=registry.ghost-prod.alphabravo.io/ghost-base/gha-runner-scale-set-controller \
  --set image.tag=<tag> \
  oci://ghcr.io/actions/actions-runner-controller-charts/gha-runner-scale-set-controller \
  --version <VERSION>

1. Verify the controller is running:

kubectl -n arc-systems get pods

You should see output similar to:

NAME                                READY   STATUS    RESTARTS   AGE
arc-gha-rs-controller-...           1/1     Running   0          30s

1. Install a runner scale set chart pointing to your repository:

helm install arc-runner-set \
  --namespace arc-runners \
  --create-namespace \
  --set githubConfigUrl=https://github.com/<your-org>/<your-repo> \
  --set githubConfigSecret=<your-secret-name> \
  oci://ghcr.io/actions/actions-runner-controller-charts/gha-runner-scale-set \
  --version <VERSION>

The githubConfigSecret must be a Kubernetes secret containing either GitHub App credentials (github_app_id, github_app_installation_id, github_app_private_key) or a personal access token (github_token). See the ARC quickstart documentation for credential setup instructions.

For complete deployment options, authentication setup, and scale set configuration, refer to the official documentation at https://docs.github.com/en/actions/hosting-your-own-runners/managing-self-hosted-runners-with-actions-runner-controller.

FIPS variant

This image includes a FIPS-compliant variant that uses Go's native FIPS 140 cryptographic mode. The FIPS variant is available with the fips tag suffix.

Use the FIPS variant when your deployment environment requires FIPS 140-compliant cryptographic operations. The FIPS module is selected at build time, so the binaries run in Go's lenient FIPS mode (fips140=on) by default rather than strict mode (fips140=only). Lenient mode is required because the controller's connection to the Kubernetes API server negotiates X25519 (not FIPS-approved); strict mode would reject it. The image also sets GODEBUG=tlsmlkem=0 to disable the post-quantum ML-KEM hybrid key exchange, which the FIPS module does not implement, so TLS falls back to classical X25519/ECDHE. FIPS-approved algorithms are still enforced for all other cryptographic operations.

Image variants

Ghost 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 Ghost hardened image

To migrate your application to a Ghost hardened image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Ghost 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

   Ghost hardened images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. To view if a package manager is available for an image variant, select the Tags tab for this repository. To view what packages are already installed in an image variant, select the Tags tab for this repository, and then select a tag.

   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 Ghost 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

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