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  • Thank you for your answer, but it's not really what I asked. I'm aware that docker has tools you can use to pass environment variables around: >I know about the ENV directive in docker, which could be used to set $ENV when building a docker image; I'd still like to know if this is possible outside docker. What I'd like to know whether this is possible just in the context of the ash shell; also, tangentially, where the PATH variable in docker's alpine image comes from, because it seems like that's where I should look for my solution. Commented Feb 28, 2019 at 0:01
  • When you run /bin/sh outside of docker it will inherit the calling environment. So the question is simply "what is the calling environment". With your docker examples, I showed that what you're seeing is docker, itself, creating the calling environment. Ultimately, "how is /bin/sh" being called will determine if $ENV is set or not. Commented Feb 28, 2019 at 0:02
  • But in a fresh docker container, there is no calling environment; it's the equivalent of a boot, isn't it? The environment must be constructed from internal config files Commented Feb 28, 2019 at 0:04
  • No. The docker engine creates a runtime environment. Commented Feb 28, 2019 at 0:05
  • Ah; the shell received from docker run -it inherits environment variables from the docker engine itself; that makes sense, and explains the behavior of alpine. Now the question is how I can get ash do do my bidding and make sure it reads unrelated variables on startup (which may occur inside docker or without) Commented Feb 28, 2019 at 0:08