Containerfile

Containerfile is a plain-text file of ordered instructions that describe how to assemble a container image — the base image to start from, files to copy in, commands to run, ports to expose, and the process to launch. It is functionally identical to Docker’s Dockerfile format but carries a vendor-neutral name adopted by Podman, Buildah, and other OCI-compliant tooling, so the same build recipe works regardless of which engine reads it.

• Instruction-based build - Directives like FROM, COPY, RUN, EXPOSE, and CMD define each layer of the resulting image in a deterministic, replayable sequence.
• Tool-agnostic naming - Podman and Buildah look for a Containerfile first, then fall back to Dockerfile, decoupling the format from any single vendor.
• OCI-compatible output - The image produced conforms to the Open Container Initiative spec, so it runs anywhere that speaks OCI.
• Reproducible infrastructure - Checked into source control alongside the code, it makes the runtime environment a versioned, reviewable artifact.

In API operations a Containerfile is where the runtime contract for a service gets pinned down — the exact base image, dependencies, and entrypoint that carry an API from a developer’s machine to CI to production without drift. Because it lives in the repository next to the OpenAPI and other governance artifacts, it becomes part of the reviewable, auditable surface of an API, and increasingly part of what an agent or pipeline inspects when deciding whether a service is built and deployed consistently.