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How to use App Platform's bindable environment variables in Dockerfile

Posted November 4, 2020 137 views
DockerDigitalOcean App Platform

I was following the tutorial on How to Use Environment Variables in App Platform, and I am unable to figure out how to use these convenience variables in my Dockerfile.

I am specifically trying to print the COMMIT_HASH to a file in the container of my web component.

ARG web.COMMIT_HASH=unspecified
RUN echo ${web.COMMIT_HASH} > /www/commithash.txt

I’ve also tried pulling it in using ENV but that fails during build.

ENV GITHASH=${web\.COMMIT_HASH:-unspecified}
RUN echo ${GITHASH} > /www/githash.txt

It errors out at the . dot.

So is there a way to get these convenience environment variables into my Dockerfile?

Any help is greatly appreciated.

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1 answer
crashoverride November 4, 2020

👋 @echoTHIS

Great question, bindable variables are a template system for environment variables, not environment variables themselves.

You could create a environment variable called GITHASH with a value of ${web.COMMIT_HASH} in the DO App Platform UI. When we build or deploy your app we will inject an environment variable of $GITHASH with your commit hash.

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  • echoTHIS November 4, 2020

    Excellent! That totally worked, thank you.

    In my app specification YAML file:

      envs:
  - key: GITHASH
    value: ${web.COMMIT_HASH}
    type: GENERAL

    And in my Dockerfile:

    ARG GITHASH=unspecified
RUN echo ${GITHASH} > /www/githash.txt

    One doctyl update later and I’m all set.

    Also I can’t believe I got an answer from @crashoverride I must say I’m a HUGE fan! Thank you for your help. Hack the planet!

    Reply Report
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