Dockerfile example used to build an elixir/phoenix project on linux and output a tarball

Dockerfile

FROM elixir:1.11.2 AS build

## instll some dependencies (webpack basically)
RUN \
  apt-get update -y && \
  curl -sL https://deb.nodesource.com/setup_14.x | bash - && \
  apt-get install -y nodejs && node -v && npm -v


# Required environment variables passed in via --build-arg flags
ARG DATABASE_URL
ARG SECRET_KEY_BASE

# prepare build dir
WORKDIR /app

# install hex + rebar
RUN mix local.hex --force && \
	mix local.rebar --force

# set build ENV
ENV MIX_ENV=prod

# install mix dependencies
COPY mix.exs mix.lock ./
COPY config config
RUN mix deps.get --only prod
RUN mix deps.compile

# copy lib first, otherwise tailwind's purgeCSS or other tree-shaking tools will purge everything.
COPY lib lib

# clean install of package-lock
COPY assets/package.json assets/package-lock.json ./assets/
RUN npm --prefix ./assets ci --progress=false --no-audit --loglevel=error

# build assets
COPY priv priv
COPY assets assets
RUN npm run --prefix ./assets deploy
RUN mix phx.digest

# compile and build release
# uncomment COPY if rel/ exists
# COPY rel rel
RUN mix do compile, release

FROM scratch AS app

WORKDIR /app
COPY --from=build /app/_build/prod/my_app-*.tar.gz ./

CMD ["/bin/bash"]