Docker container with entrypoint variable expansion and CMD parameters

Question

I want to create a Docker Image that acts as an executable for which the user passes a token as an environment variable. The executable has sub commands that the user should

Answer 1

As specified in the docker documentation, you are specifying an entrypoint that calls a shell (thus not in the shell form, but the exec one). The parameters are passed to the shell (and therefore ignored); only the command in the shell matters. You will see your issue solved after switching your entrypoint call to:

ENTRYPOINT ["usr/bin/mycmd", "--token=$MY_TOKEN"]

Calling a shell in an entrypoint is something heavily discouraged, and precisely only useful when you want to avoid users of the image append custom parameters to your entrypoint.

See you in the interwebs! :)

Answer 2

With /bin/sh -c "script" syntax, anything after the -c argument becomes an argument to your script. You can reach them with $0 and $@ as part of your /bin/sh script:

ENTRYPOINT ["/bin/sh", "-c", "exec /usr/bin/mycmd --token=$MY_TOKEN $0 $@"]
CMD ["pull", "stuff"]

Note that you could also change your entrypoint to be a shell script added to your image that runs exec /usr/bin/mycmd --token=$MY_TOKEN "$@" and execute that shell script with docker's exec syntax:

ENTRYPOINT ["/entrypoint.sh"]