can't get the FROM image name.

[ozbillwang]

When run this docker command, I got list of Dockerfile commands, but there is no FROM part on the top.

So how can I know the image start from?

$ docker run -v /var/run/docker.sock:/var/run/docker.sock centurylink/dockerfile-from-image selenium/base

ADD file:b43bf069650bac07b66289f35bfdaf474b6b45cac843230a69391a3ee342a273 in /
RUN 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
RUN sed -i 's/^#\s*\(deb.*universe\)$/\1/g' /etc/apt/sources.list
CMD ["/bin/bash"]
MAINTAINER Selenium <selenium-developers@googlegroups.com>
RUN echo "deb http://archive.ubuntu.com/ubuntu trusty main universe\n" > /etc/apt/sources.list && echo "deb http://archive.ubuntu.com/ubuntu trusty-updates main universe\n" >> /etc/apt/sources.list
RUN apt-get update -qqy && apt-get -qqy --no-install-recommends install ca-certificates openjdk-7-jre-headless unzip wget && rm -rf /var/lib/apt/lists/* && sed -i 's/\/dev\/urandom/\/dev\/.\/urandom/' ./usr/lib/jvm/java-7-openjdk-amd64/jre/lib/security/java.security
RUN mkdir -p /opt/selenium && wget --no-verbose http://selenium-release.storage.googleapis.com/2.46/selenium-server-standalone-2.46.0.jar -O /opt/selenium/selenium-server-standalone.jar
RUN sudo useradd seluser --shell /bin/bash --create-home && sudo usermod -a -G sudo seluser && echo 'ALL ALL = (ALL) NOPASSWD: ALL' >> /etc/sudoers && echo 'seluser:secret' | chpasswd

[bdehamer]

There really is no good way to get that information since it isn't encoded in any of the metadata that Docker stores with the image. If you don't see a FROM statement in the output, you can assume that it is FROM scratch.

[ozbillwang]

Thanks, this answered my question.