nvflare

NVFlare 2.8.0 manages federated learning systems via the poc command. The start_server/start_client subcommands from earlier releases are not present in this version.

Prepare a local proof-of-concept environment with one server and two clients:

mkdir -p /path/to/poc
sudo chown 65532:65532 /path/to/poc

docker run --rm -it \
  -v /path/to/poc:/poc \
  -e NVFLARE_POC_WORKSPACE=/poc/ws \
  registry.ghost-prod.alphabravo.io/ghost-base/nvflare:<tag> \
  poc prepare -n 2

The workspace is written to /path/to/poc/ws on the host. The chown step is required because the container runs as uid 65532.

Refer to the NVFlare POC documentation for full POC startup and provisioning guides.

Kubernetes deployment

NVFlare is designed for Kubernetes-native federated learning. Refer to the NVFlare documentation for full deployment guides using the provisioning tool and Helm charts.

Troubleshooting

Container exits immediately

The image entrypoint is /opt/nvflare/bin/nvflare. Pass a valid subcommand such as --version or --help to verify the image works. Note that start_server and start_client are not valid subcommands in NVFlare 2.8.0; use nvflare poc or a provisioned startup kit instead.

Entrypoint differs from upstream

Upstream nvflare/nvflare images default to python3 (no entrypoint). This hardened image defaults to the nvflare CLI. CLI workflows such as poc prepare and simulator work without change. If you previously ran Python scripts or an interactive interpreter against the upstream image, override the entrypoint or use a dev tag:

docker run --rm --entrypoint /opt/nvflare/bin/python3 registry.ghost-prod.alphabravo.io/ghost-base/nvflare:<tag> -c "import nvflare; print(nvflare.__version__)"
docker run --rm --entrypoint /opt/nvflare/bin/python3 registry.ghost-prod.alphabravo.io/ghost-base/nvflare:<tag>-dev my_script.py

Permission denied on mounted volumes

The container runs as uid 65532. Ensure mounted directories are readable by that user:

chown -R 65532:65532 /path/to/workspace

Image variants

Ghost 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 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.

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. 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 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

Upstream nvflare/nvflare has no entrypoint and defaults to python3. This hardened image sets the entrypoint to /opt/nvflare/bin/nvflare, so container arguments are passed to the NVFlare CLI. For a Python interpreter or script, override with --entrypoint /opt/nvflare/bin/python3 or use a dev tag. Use docker inspect to confirm the entrypoint when migrating Dockerfiles or orchestration manifests.