Example of a development dockerfile & compose replicating the host's user

docker-compose.yml

# Other parts of the file omitted for clarity:
version: "2.4"

services:
  # The test container - we'll use this as a base for the rest of the containers:
  test: &app
    image: vovimayhem/example-app:development
    build:
      context: .
      dockerfile: Dockerfile
      target: development
      args:
      - DEVELOPER_UID=${UID:-1000}
      - DEVELOPER_USER=${USER:-you}

    entrypoint: /usr/src/bin/dev-entrypoint.sh
    command: rspec
    networks: [ "backend" ]
    depends_on: [ "postgres" ]

    volumes:
    # Mount our app code directory (".") into our app containers at the
    # "/usr/src" folder:
    - .:/usr/src

    # Keep the stdin open, so we can attach to our app container's process
    # and do things such as byebug, etc:
    stdin_open: true

    # Enable sending signals (CTRL+C, CTRL+P + CTRL+Q) into the container:
    tty: true

    # Specify environment variables available for our app containers. We'll leave
    # a YML anchor in case we need to override or add more variables if needed on
    # each app container:
    environment: &app_env
      DATABASE_URL: postgres://postgres:3x4mpl3P455w0rd@postgres:5432/blackcomb_test
      RAILS_ENV: test
      RACK_ENV: test
      RAILS_LOG_TO_STDOUT: 'true'
      MAILER_HOST: localhost
      MAILER_PORT: 3000

Dockerfile

# Other parts of the file omitted for clarity:

# I: Runtime Stage: ============================================================
FROM ruby:2.6.1-alpine AS runtime

WORKDIR /usr/src

ENV HOME=/usr/src PATH=/usr/src/bin:$PATH

RUN apk add --no-cache ca-certificates less libpq nodejs npm openssl su-exec tzdata

# II: Development Stage: =======================================================
FROM runtime AS development

RUN apk add --no-cache \
    build-base \
    chromium \
    chromium-chromedriver \
    git \
    postgresql-dev \
    yarn

RUN npm config set unsafe-perm true

RUN npm install -g check-dependencies

ADD Gemfile* /usr/src/

RUN bundle install --jobs=4 --retry=3

ARG DEVELOPER_UID="1000"
ARG DEVELOPER_USER="you"
	
RUN adduser -H -D -h /usr/src -u $DEVELOPER_UID $DEVELOPER_USER \
 && addgroup $DEVELOPER_USER root
	
ENV DEVELOPER_USER=$DEVELOPER_USER