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Anthony Kong
Asked: 2017-08-17 17:45:27 +0800 CST

How to set environment variable within the docker file?

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The CMD of my dockerfile is this: ["python", "myproject/start_slide_server.py"]

However for this to work, I need to set the PYTHONPATH to /app, which is the parent directory of myproject

If I start the docker process and override CMD with bash, I can run the following

root@42e8998a8ff7:/app# export PYTHONPATH=.
root@42e8998a8ff7:/app# python myproject/start_slide_server.py
 * Running on http://0.0.0.0:8090/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 236-035-556

And it works as expected

Now I add the line 

RUN export PYTHONPATH=/app

before 

CMD ["python" , "myproject/start_slide_server.py"]

it just failed 

Traceback (most recent call last):
  File "/app/myproject/start_slide_server.py", line 23, in <module>
    from myproject import env
ImportError: No module named myproject

It seems like the RUN line does not have any impact at all

I really do not want to define ENV at the dockercommand level because this PYTHONPATH will not change from one image to next.

How can I achieve this?

I can use the ENV directive

ENV PYTHONPATH /app
docker

1 Answers

  1. You should not over-write the PYTHONPATH with your path but append it; otherwise the system will not find the installed Python packages.

    • Option 1: RUN export PYTHONPATH="$PYTHONPATH:/app"
    • Option 2: ENV PYTHONPATH="$PYTHONPATH:/app"
    • 4