To install Yarn, your Layerfile will include something like this:
FROM vm/ubuntu:18.04 # To note: Layerfiles create entire VMs, *not* containers! RUN curl -fSsL https://deb.nodesource.com/setup_14.x | bash && \ curl -fSsL https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - && \ echo "deb https://dl.yarnpkg.com/debian/ stable main" > /etc/apt/sources.list.d/yarn.list && \ apt-get update && \ apt-get install nodejs yarn COPY . . RUN yarn install --frozen-lockfile RUN BACKGROUND yarn start EXPOSE WEBSITE http://localhost:3000
Information on optimizing and troubleshooting Yarn in webapp.io can be found here.