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Cannot access downloaded repository in my Docker file from additional RUN commands

I’m setting up a docker image, I’ve managed to get it working, but only by running one long RUN command with everything in it.
I want to break it into smaller RUN commands for ease of maintenance and debugging, etc.

My first RUN command looks like this:

 RUN apt-get update --quiet && 
  apt-get install --quiet --yes --no-install-recommends 
  build-essential 
  libssl-dev 
  zlib1g-dev 
  libreadline-dev 
  libffi-dev 
  libyaml-dev && 
  git clone --depth 1 https://github.com/rbenv/rbenv.git ~/.rbenv && 
  git clone --depth 1 https://github.com/rbenv/ruby-build.git  && 
  echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.bashrc && 
  echo 'eval "$(rbenv init -)"' >> ~/.bashrc && 
  /bin/bash -c "source ~/.bashrc"

When I try call the rbenv install script in the next RUN command docker can’t find it. Why is this? I’ve tried adding the path in the new RUN command, but it doesn’t seem to make a difference.
What am I doing wrong?

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2

Answers


  1. 0

    The issue here with the PATH env variable. Each RUN instruction in a Dockerfile executes in a new shell session, and environment changes (like modifications to PATH in .bashrc) do not persist across these sessions.

    You need to explicitly set PATH via Docker ENV instruction, like this:

    ENV PATH="$HOME/.rbenv/bin:$PATH"

    You can find more info in this stackoverflow answer,
    and in this Baeldung article.

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  2. 0

    ~/.bashrc is only executed for login shell and if the login shell is bash. If you want it to be executed in the next RUN commands, you must specify it explicitly, like this:

    RUN bash -l -c '...'

    or

    RUN . ~/.bashrc; ...

    Also note that if there is no ~/.bashrc, bash will execute ~/.profile. But ~/.bashrc normally also includes . ~/.profile somewhere near the end so it’s usually safer to just append ~/.profile — it will work for both bash and other shells.

    For the Dockerfile though, if you don’t intend to work in the container interactively, you can ignore bash altogether and add environment variables (including PATH) using the ENV directive.

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