Docker echo environment variable

Question

I\'m trying to write a little docker file that sets a User and just echos the current user as a little example to prove to myself it is working. I\'ve tried a number of variants

Answer 1

I think there´s a series of issues here.

when I

docker run -i -t ubuntu /bin/bash
echo $USER
set

I don´t see $USER set at all - whoami does report daemon though.

additionally, I have the suspicion (but have not looked at the code yet) that ENV vars in the Dockerfile are escaped, to avoid their use (many people assume that they can export host variables to the built container, but this is something that the docker guys would like to avoid)