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I've search some of the questions already like docker ENV vs RUN export, which explains differences between those commands, but didn't help in solving my problem.
For example I have a script called myscript:
#!/bin/bash
export PLATFORM_HOME="$(pwd)"
And have following lines in Dockerfile:
...
COPY myscript.sh /
RUN ./myscript.sh
I've also tried to use ENTRYPOINT instead of RUN or declaring variable before calling the script, all that with no success.
What I want to achieve is that PLATFORM_HOME can be referenced from other Dockerfiles which use that one as a base. How to do it ?
368
Using docker-compose , you can inherit env variables in docker-compose. yml and subsequently any Dockerfile(s) called by docker-compose to build images. This is useful when the Dockerfile RUN command should execute commands specific to the environment.
With a Command Line Argument The command used to launch Docker containers, docker run , accepts ENV variables as arguments. Simply run it with the -e flag, shorthand for --env , and pass in the key=value pair: sudo docker run -e POSTGRES_USER='postgres' -e POSTGRES_PASSWORD='password' ...
env file is placed at the base of the project directory. Project directory can be explicitly defined with the --file option or COMPOSE_FILE environment variable. Otherwise, it is the current working directory where the docker compose command is executed ( +1.28 ). For previous versions, it might have trouble resolving ...
Fetch Using docker exec Command Here, we are executing the /usr/bin/env utility inside the Docker container. Using this utility, you can view all the environment variables set inside Docker containers. Notice that our my_env_var is also present in the output.
There's no way to export a variable from a script to a child image. As a general rule, environment variables travel down, never up to a parent.
ENV will persist in the build environment and to child images and containers.
Dockerfile
FROM busybox
ENV PLATFORM_HOME test
RUN echo $PLATFORM_HOME
Dockerfile.child
FROM me/platform
RUN echo $PLATFORM_HOME
CMD ["sh", "-c", "echo $PLATFORM_HOME"]
Build the parent
docker build -t me/platform .
Then build the child:
→ docker build -f Dockerfile.child -t me/platform-test .
Sending build context to Docker daemon 3.072kB
Step 1/3 : FROM me/platform
---> 539b52190af4
Step 2/3 : RUN echo $PLATFORM_HOME
---> Using cache
---> 40e0bfa872ed
Step 3/3 : CMD sh -c echo $PLATFORM_HOME
---> Using cache
---> 0c0e842f99fd
Successfully built 0c0e842f99fd
Successfully tagged me/platform-test:latest
Then run
→ docker run --rm me/platform-test
test
I think export sets the environment variables for the child processes. So it really doesn't matter if you do RUN or ENTRYPOINT. In reading linux source command not working when building Dockerfile, I feel source command cannot help either.
You need to use ENV if you want to set the environment variables in Dockerfile.
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