I am currently investigating image layers correspond to a Docker image. I see that some instructions do not begin with RUN command. Please find a portion of code snippet below.
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ARG RELEASE
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ARG LAUNCHPAD_BUILD_ARCH
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LABEL org.opencontainers.image.ref.name=ubuntu
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LABEL org.opencontainers.image.version=20.04
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ADD file:8b1<some_hash>c in /
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CMD ["/bin/bash"]
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ENV <some_environment>
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ENV <sone_environment>
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ENV DEBIAN_FRONTEND=noninteractive
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ENV TZ=Europe/London
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apt-get clean
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apt-get update && apt-get upgrade -y && apt-get dist-upgrade -y
In the lines 11 and 12 in this code snippet contains shell commands. I was expecting to see RUN /bin/sh command prior to apt-get clean and apt-get update .. commands. I'd like to know why these layers do not contain RUN /bin/sh.
My objective is to reproduce Docker image from the image layers as I don't have the access to the original Docker image.