medium-multi-stage-dockerfile-release-stage

Dockerfile

###############################
# Stage release
FROM runner as release
LABEL description="Builds a release image removing unneeded files and dependencies"

# Removes development and test gems by re-running the bundle
# install command using cached gems and simply removing unneeded
# gems using the clean option.
RUN bundle install --local --clean --without development test \
 # Remove unneeded cached gems
 && find vendor/bundle/ -name "*.gem" -delete \
 # Remove unneeded files and folders
 && rm -rf spec tmp/cache node_modules app/assets vendor/assets lib/assets
 
# Copy compiled assets
COPY --chown=app:app --from=compiler /home/app/public /home/app/public

ARG ASSET_HOST
ARG ENV=production

# Set App env variables
ENV ASSET_HOST $ASSET_HOST
ENV RAILS_ENV $ENV