4.20.12 failing with coreos Read-only file system

[joshgubler]

After upgrading to 4.20.12, the new pod is failing to start with the following error:

machine-os-images /bin/copy-metal: line 43: /coreos/coreos-aarch64.iso.sha256: Read-only file system
stream closed: EOF for openshift-machine-api/metal3-image-customization-786c558f-t7nk4 (machine-os-images)

The specific failing image is quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:c4758545477381c5f58966fac7a80375abbef1f8de591cdc95c71e88612e304c

Analysis from Codex:

It’s coming from the machine-os-images initContainer: its securityContext.readOnlyRootFilesystem: true, and there is no volume mounted at /coreos in that container. The only writable mount shown is /shared/html/images. So when /bin/copy-metal tries to write /coreos/coreos-aarch64.iso.sha256, it hits the read‑only root filesystem and fails.

So the immediate cause is: the new image/entrypoint writes to /coreos but the container root FS is read‑only and /coreos isn’t a writable mount.

That’s a behavior change vs the previous image.