packer/website/source/partials/builder/docker/_Config-required.html.md

• commit (bool) - If true, the container will be committed to an image rather than exported.

• discard (bool) - Throw away the container when the build is complete. This is useful for the artifice post-processor.

• export_path (string) - The path where the final container will be exported as a tar file.

• image (string) - The base image for the Docker container that will be started. This image will be pulled from the Docker registry if it doesn't already exist.

• message (string) - Set a message for the commit.