FROM attribute in the output Dockerfile is the image itself

[sandal-maker]

Describe the bug
When used to get the Dockerfile for gitlab/gitlab-runner:latest, the FROM attribute in the output Dockerfile is gitlab/gitlab-runner:latest and not alpine:3.12.0 as it should be.

To Reproduce
Steps to reproduce the behavior run the following script:

docker pull quay.io/laniksj/dfimage
alias dfimage="docker run -v /var/run/docker.sock:/var/run/docker.sock --rm quay.io/laniksj/dfimage"
dfimage gitlab/gitlab-runner:latest

Expected behavior
Expected to see the following:
FROM alpine:3.12.0

Actual behavior
This is the actual output.
Check the first line FROM attribute.

FROM gitlab/gitlab-runner:latest
ADD file:1b4ec50586b9f0621095f51ee6baecc00a7f6d95b4a04e3bedc5393b28bc8a54 in /
RUN /bin/sh -c set -xe 		\
    && echo '#!/bin/sh' > /usr/sbin/policy-rc.d 	\
    && echo 'exit 101' >> /usr/sbin/policy-rc.d 	\
    && chmod +x /usr/sbin/policy-rc.d 		\
    && dpkg-divert --local --rename --add /sbin/initctl 	\
    && cp -a /usr/sbin/policy-rc.d /sbin/initctl 	\
    && sed -i 's/^exit.*/exit 0/' /sbin/initctl 		\
    && echo 'force-unsafe-io' > /etc/dpkg/dpkg.cfg.d/docker-apt-speedup 		\
    && echo 'DPkg::Post-Invoke { "rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true"; };' > /etc/apt/apt.conf.d/docker-clean 	\
    && echo 'APT::Update::Post-Invoke { "rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true"; };' >> /etc/apt/apt.conf.d/docker-clean 	\
    && echo 'Dir::Cache::pkgcache ""; Dir::Cache::srcpkgcache "";' >> /etc/apt/apt.conf.d/docker-clean 		\
    && echo 'Acquire::Languages "none";' > /etc/apt/apt.conf.d/docker-no-languages 		\
    && echo 'Acquire::GzipIndexes "true"; Acquire::CompressionTypes::Order:: "gz";' > /etc/apt/apt.conf.d/docker-gzip-indexes 		\
    && echo 'Apt::AutoRemove::SuggestsImportant "false";' > /etc/apt/apt.conf.d/docker-autoremove-suggests
RUN /bin/sh -c [ -z "$(apt-get indextargets)" ]
RUN /bin/sh -c mkdir -p /run/systemd \
    && echo 'docker' > /run/systemd/container
CMD ["/bin/bash"]
RUN ARG TARGETPLATFORM
RUN ENV DEBIAN_FRONTEND=noninteractive
RUN RUN |1 TARGETPLATFORM=linux/amd64 /bin/sh -c apt-get update -y \
    &&     apt-get install -y --no-install-recommends         apt-transport-https         ca-certificates         curl         git         wget         tzdata         openssh-client     \
    && rm -rf /var/lib/apt/lists/* # buildkit
RUN ARG DOCKER_MACHINE_VERSION
RUN ARG DUMB_INIT_VERSION
RUN ARG GIT_LFS_VERSION
RUN COPY gitlab-runner_*.deb checksums-* install-deps install-gitlab-runner /tmp/ # buildkit
RUN RUN |4 TARGETPLATFORM=linux/amd64 DOCKER_MACHINE_VERSION=0.16.2 DUMB_INIT_VERSION=1.2.2 GIT_LFS_VERSION=2.11.0 /bin/sh -c /tmp/install-deps "${TARGETPLATFORM}" "${DOCKER_MACHINE_VERSION}" "${DUMB_INIT_VERSION}" "${GIT_LFS_VERSION}" # buildkit
RUN COPY entrypoint / # buildkit
RUN RUN |4 TARGETPLATFORM=linux/amd64 DOCKER_MACHINE_VERSION=0.16.2 DUMB_INIT_VERSION=1.2.2 GIT_LFS_VERSION=2.11.0 /bin/sh -c chmod +x /entrypoint # buildkit
RUN STOPSIGNAL SIGQUIT
RUN VOLUME [/etc/gitlab-runner /home/gitlab-runner]
RUN ENTRYPOINT ["/usr/bin/dumb-init" "/entrypoint"]
RUN CMD ["run" "--user=gitlab-runner" "--working-directory=/home/gitlab-runner"]

• OS: macos
• Docker Version: 19.03.13

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[LanikSJ]

Looks like Docker changed how they read the layers. I'll have to look into it and see if I can figure out what they've changed.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[LanikSJ]

Closing this in favor of #251