Yarn installation has changed since this book has been written. We no longer need to specify the setup scripts or address the dependency issue mentioned by Rob.
Here is my Dockerfile working with Yarn
FROM ruby:2.6 LABEL maintainer="email@example.com" RUN apt-get update -yqq && apt-get install -yqq --no-install-recommends nodejs RUN apt-get update -yqq && apt-get install -yqq --no-install-recommends apt-transport-https RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - RUN echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list RUN apt update -yqq && apt install -f yarn COPY Gemfile* /usr/src/app/ WORKDIR /usr/src/app RUN bundle install COPY . /usr/src/app/ CMD ["bin/rails", "s", "-b", "0.0.0.0"]