FROM ruby:2.4-alpine# Edit with nodejs, mysql-client, postgresql-client, sqlite3, etc. for your needs.# Or delete entirely if not needed.RUN apk --no-cache add nodejs postgresql-client# throw errors if Gemfile has been modified since Gemfile.lockRUN bundle config --global frozen 1RUN mkdir -p /usr/src/appWORKDIR /usr/src/appCOPY Gemfile Gemfile.lock /usr/src/app/RUN bundle installCOPY . /usr/src/app# For Sinatra#EXPOSE 4567#CMD ["ruby", "./config.rb"]# For RailsEXPOSE 3000CMD ["rails", "server"]