Pass ARG to ENTRYPOINT

Question

Say I have this in a Dockerfile:

ARG FOO=1
ENTRYPOINT ["docker.r2g", "run"]

where I build the above with:

docker build -t "$tag" --build-arg FOO="$(date +%s)" .

is there a way to do something like:

ENTRYPOINT ["docker.r2g", "run", ARG FOO]  // something like this

I guess the argument could also be passed with docker run instead of during the docker build phase?

Answer 1

You could combine ARG and ENV in your Dockerfile, as I mention in "ARG or ENV, which one to use in this case?"

ARG FOO
ENV FOO=${FOO}

That way, you docker.r2g can access the ${FOO} environment variable.

I guess the argument could also be passed with docker run instead of during the docker build phase?

That is also possible, if it makes more sense to give FOO a value at runtime:

docker run -e FOO=$(...) ...