Dockerfile replicate the host user UID and GID to the image

Question

You can pass it as a build arg. Your Dockerfile can be static:

FROM ubuntu:xenial-20170214
ARG UNAME=testuser
ARG UID=1000
ARG GID=1000
RUN groupadd -g $GID -o $UNAME
RUN useradd -m -u $UID -g $GID -o -s /bin/bash $UNAME
USER $UNAME
CMD /bin/bash

Then you’d pass the options on your build command:

docker build --build-arg UID=$(id -u) --build-arg GID=$(id -g) \
  -f bb.dockerfile -t testimg .

Note that I’ve solved similar problems to this a different way, by running an entrypoint as root that looks a file/directory permissions of the host volume mount, and adjust the uid/gid of the users inside the container to match the volume uid/gid. After making that change, it drops access from the root user to the modified uid/gid user and runs the original command/entrypoint. The result is the image can be run unchanged on any developer machine. An example of this can be found in my jenkins-docker repo:

https://github.com/sudo-bmitch/jenkins-docker

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