Podman and Docker Build Argument Compatibility: Interoperability Question

Direct Answer

For standard OCI images built with rootless Podman using the Buildah backend, build-time ARG values, image metadata fields, and common Dockerfile directives behave identically when the resulting image is inspected or run by Docker Engine. No image modification is required.

ARG values in docker inspect

ARG values passed with --build-arg are persisted in the image configuration and appear unchanged in docker inspect under Config.Env, provided the Dockerfile declares the corresponding ARG instruction. Both builders write these values into the same OCI image configuration JSON.

Rootless Podman metadata fields

Rootless Podman produces standard OCI-compliant image layout. Fields such as createdby, architecture, and os are populated according to the OCI specification, and Docker Engine processes them identically. You may see differences in created timestamps or container-state metadata, but these do not affect runtime behavior.

SHELL and HEALTHCHECK semantics

For standard use cases, SHELL and HEALTHCHECK directives are interpreted consistently by Buildah and Docker's native builder. Both write the resulting configuration into the image's config section in the same way.

What May Differ

Confirmed facts cover the OCI standard path. Likely sources of subtle divergence include Buildah-specific annotations or labels that Docker ignores silently, and file permission differences caused by rootless UID mapping. Custom base images or non-standard Dockerfile syntax are the most probable places where incompatibilities surface.

Verification Steps

1. Build with an explicit argument: podman build --build-arg MYVAR=value -t test-image Dockerfile
2. Inspect the environment: docker inspect test-image --format '{{json .Config.Env}}'
3. Compare build history metadata: docker history test-image and podman inspect test-image
4. Run the image on both runtimes to confirm behavior: docker run --rm test-image and podman run --rm test-image

If you are using a custom base image or non-standard Dockerfile syntax, share the specific directive or field that differs; that detail would change the recommendation from "expect identical behavior" to targeted debugging of that specific builder path.