Sometimes being root inside a docker container is a pain especially when mounting files and having to create and modify files inside the container.

So what is an easy way around this issue? Well docker allows you to launch a container and become the UID and GID you pass in:

$ docker run --rm -ti --user (id -u $USER):(id -g $USER) ubuntu:16.04
groups: cannot find name for group ID 1000
I have no name!@f8b2e4f05d4e:/$

Though this approach works it means you can’t setup a bashrc or special completion tools as they are not configured for new users that do not have a home directory.

The Solution

FROM ubuntu:16.04
LABEL maintainer="Crunchy234"

# Update the apt packages in the container.
RUN apt-get update && apt-get upgrade -y
RUN apt-get install -y \
sudo \
apt-utils

# Create directories for the container
RUN mkdir /home/working

# Set default UID and GID to create user with
ENV USERID 1001
ENV GROUPID 1001

RUN mkdir -p /home/developer && \
echo "developer:x:${USERID}:${GROUPID}:Developer,,,:/home/developer:/bin/bash" >> /etc/passwd && \
echo "developer:x:${USERID}:" >> /etc/group && \
chown ${USERID}:${GROUPID} -R /home/working && \
cp /root/.bashrc /home/developer && \
usermod -m -d /home/developer developer && \
echo "developer ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/developer && \
chmod 0440 /etc/sudoers.d/developer && \
chown ${USERID}:${GROUPID} -R /home/developer

WORKDIR /home/working
ENTRYPOINT usermod -u $USERID developer && \
groupmod -g $GROUPID developer && \
su developer && \
bash

To create this container:

$ docker build -t docker-as-user .

To run the container:

$ docker run --rm -ti -e USERID=$(id -u $USER) -e GROUPID=$(id -g $USER) docker-as-user
su: Authentication failure
(Ignored)
developer@2de334de689b:/home/working$

Now inside this container when you create and destroy files you are doing so as the user and you have full completion as well.

Current issues

You have to exit the container twice to exit. The first exit exits the user.
It’s not a clean entrypoint so non interactive scripts may be an issue.

Feel free to contribute to the repository and improve it on GitHub: https://github.com/crunchy234/docker-as-user

The Solution#

Current issues#

The Solution

Current issues