Bug: Testing with podman shows different schematics than Docker-CE #10

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samip5 · 2026-08-03T20:20:13+03:00

samip5 commented

2026-08-03 20:20:13 +03:00

There seems to be some differences in schematics when the container engine used is Podman and not Docker Engine as container_image.Config.User doesn't seem to behave the same for both.

Claude's analysis of the issue:

the docker_image/docker_image_info return value gives you the raw docker image inspect output. In the legacy Docker image format, Config.User is always present, defaulting to "" when no USER instruction was set. But modern Docker (with the containerd image store / buildkit-produced OCI images) serializes image config using OCI's omitempty semantics — fields left at their zero value, like an unset User, are dropped from the JSON entirely rather than serialized as "". So for any image that never sets USER (the overwhelming majority — they just run as root), Config on your host now comes back without a User key at all.

There seems to be some differences in schematics when the container engine used is Podman and not Docker Engine as `container_image.Config.User` doesn't seem to behave the same for both. Claude's analysis of the issue: ``` the docker_image/docker_image_info return value gives you the raw docker image inspect output. In the legacy Docker image format, Config.User is always present, defaulting to "" when no USER instruction was set. But modern Docker (with the containerd image store / buildkit-produced OCI images) serializes image config using OCI's omitempty semantics — fields left at their zero value, like an unset User, are dropped from the JSON entirely rather than serialized as "". So for any image that never sets USER (the overwhelming majority — they just run as root), Config on your host now comes back without a User key at all. ```

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Reference: uumas/ansible-docker#10