Using docker args with non-root user

[aedrax]

We're trying to use docker_args: '--group-add dialout' but it only adds the root user to dialout, is there a way to specify the user?

[haboustak]

scuba could make this easier on you, as it is already managing users and groups inside the container, but it may be possible using external environment variables and root hooks:

environment:
  USER:

hooks:
  root:
    script:
      - \[ -n "$USER" \] || ( echo "No USER in environment" ; exit 1 )
      - gpasswd -a $USER dialout

It would be nicer to do it without relying on the external env (e.g. $SCUBA_USER), and even nicer to do it without the hook.