Dockerfile named-multi-staged (one Dockerfile to rule them all!)

Dockerfile

# === Base Layer started

FROM ruby:3.0.1 as base

WORKDIR /app

RUN curl -sL https://deb.nodesource.com/setup_12.x | bash - && \
    apt-get install -y nodejs libsodium-dev && \
    npm i -g yarn

COPY Gemfile Gemfile.lock ./

# === Development Layer started

FROM base as dev

RUN apt-get install -y postgresql-client

RUN bundle install && yarn

# === Builder Layer started
FROM base

RUN bundle config set --local without 'development test' && \
    bundle install -j4 --no-cache

COPY . .

# === Runtime Layer started
FROM ruby:3.0.1

WORKDIR /app

RUN curl -sL https://deb.nodesource.com/setup_12.x | bash - && \
    apt-get install -y nodejs && \
    npm i -g yarn

COPY --from=builder /usr/local/bundle/ /usr/local/bundle/
COPY --from=builder /app/ /app/

CMD bin/rake assets:precompile && bin/rails server -p ${PORT:-5000} -e $RAILS_ENV