#docker - September 2023

How can I reduce the size of the image in this Dockerfile? It was generated by fly.io. The image size is 3.4 GB
Dockerfile

# syntax = docker/dockerfile:1

# Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
ARG RUBY_VERSION=3.2.0
FROM ruby:$RUBY_VERSION-slim as base

LABEL fly_launch_runtime="rails"

# Rails app lives here
WORKDIR /rails

ARG RAILS_MASTER_KEY
# Set production environment
ENV RAILS_ENV="production" \
    BUNDLE_WITHOUT="development:test" \
    BUNDLE_DEPLOYMENT="1" \
    RAILS_MASTER_KEY=${RAILS_MASTER_KEY}

# Update gems and bundler
RUN gem update --system --no-document && \
    gem install -N bundler

# Install packages needed to install nodejs
RUN apt-get update -qq && \
    apt-get install --no-install-recommends -y curl && \
    rm -rf /var/lib/apt/lists /var/cache/apt/archives

# Install Node.js
ARG NODE_VERSION=14.21.1
ENV PATH=/usr/local/node/bin:$PATH
RUN curl -sL <https://github.com/nodenv/node-build/archive/master.tar.gz> | tar xz -C /tmp/ && \
    /tmp/node-build-master/bin/node-build "${NODE_VERSION}" /usr/local/node && \
    rm -rf /tmp/node-build-master


# Throw-away build stage to reduce size of final image
FROM base as build

# Install packages needed to build gems and node modules
RUN apt-get update -qq && \
    apt-get install --no-install-recommends -y build-essential git libpq-dev libvips node-gyp pkg-config python-is-python3

# Install yarn
ARG YARN_VERSION=1.22.19
# node modules are installed in root of the image
ENV NODE_ENV="production" \
    PREFIX=/usr/local \
    PATH=/usr/local/node/bin:$PATH
RUN npm install -g yarn@$YARN_VERSION && \
    rm -rf /usr/local/node/lib/node_modules/npm && \
    yarn --version && \
    apt-get remove -y node-gyp pkg-config && \
    apt-get autoremove -y && \
    rm -rf /tmp/npm* /tmp/gyp /tmp/node-* /tmp/node_modules/npm* /var/lib/apt/lists/* \
    /usr/local/node/lib/node_modules/npm

# Build options
ENV PATH="/usr/local/node/bin:$PATH"

# Install application gems
COPY --link Gemfile Gemfile.lock ./
RUN bundle install && \
    bundle exec bootsnap precompile --gemfile && \
    rm -rf ~/.bundle/ $BUNDLE_PATH/ruby/*/cache $BUNDLE_PATH/ruby/*/bundler/gems/*/.git

# Install node modules
COPY --link package.json yarn.lock ./
RUN yarn install --frozen-lockfile

# Copy application code
COPY --link . .

# Precompile bootsnap code for faster boot times
RUN bundle exec bootsnap precompile app/ lib/

# Precompiling assets for production without requiring secret RAILS_MASTER_KEY
RUN SECRET_KEY_BASE=DUMMY ./bin/rails assets:precompile


# Final stage for app image
FROM base

# Install packages needed for deployment
RUN apt-get update -qq && \
    apt-get install --no-install-recommends -y curl imagemagick libvips postgresql-client mtr iputils-ping && \
    rm -rf /var/lib/apt/lists /var/cache/apt/archives

# Copy built artifacts: gems, application
COPY --from=build /usr/local/bundle /usr/local/bundle
COPY --from=build /rails /rails

# Run and own only the runtime files as a non-root user for security
RUN useradd rails --create-home --shell /bin/bash && \
    chown -R rails:rails db log tmp
USER rails:rails

# Deployment options
ENV RAILS_LOG_TO_STDOUT="1" \
    RAILS_SERVE_STATIC_FILES="true"

# Entrypoint prepares the database.
ENTRYPOINT ["/rails/bin/docker-entrypoint"]

# Start the server by default, this can be overwritten at runtime
EXPOSE 3000

.dockerignore

# See <https://docs.docker.com/engine/reference/builder/#dockerignore-file> for more about ignoring files.

# Ignore git directory.
/.git/

# Ignore bundler config.
/.bundle

# Ignore all default key files.
/config/master.key
/config/credentials/*.key

# Ignore all environment files.
/.env*
!/.env.example

# Ignore all logfiles and tempfiles.
/log/*
/tmp/*
!/log/.keep
!/tmp/.keep

# Ignore all cache files.
/tmp/cache/*

# Ignore pidfiles, but keep the directory.
/tmp/pids/*
!/tmp/pids/
!/tmp/pids/.keep

# Ignore storage (uploaded files in development and any SQLite databases).
/storage/*
!/storage/.keep
/tmp/storage/*
!/tmp/storage/
!/tmp/storage/.keep

# Ignore assets.
/node_modules/
/app/assets/builds/*
!/app/assets/builds/.keep
/public/assets

# Ignore data_files/
/data_files/*
!/data_files/.keep

# Ignore coverage
/coverage/*

# Ignore spec files
/spec/*
!/spec/.keep

Hey folks, Docker recently removed the buildinfo metadata from buildx outputs because they were moving stuff like that to attestations and provenance outputs. Has anyone been able to actually get that data back out, though? I recently went about changing our build action to try pulling that data and I'm only seeing partial results. In particular, we have a multi-platform build that should output both amd64 and arm64 outputs. The output below shows the former, but the latter renders as just unknown:

{
  "mediaType": "application/vnd.oci.image.index.v1+json",
  "schemaVersion": 2,
  "manifests": [
    {
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "digest": "sha256:819b2e9960f85e1667e924ebba1cd9e0bca7924a7afdaf5a194630bb2ed1e750",
      "size": 1800,
      "platform": {
        "architecture": "amd64",
        "os": "linux"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "digest": "sha256:8de8b55a1b364eacb4b2b89e839f52120492a4c6c05110e982b3f3e9b663eb51",
      "size": 566,
      "annotations": {
        "vnd.docker.reference.digest": "sha256:819b2e9960f85e1667e924ebba1cd9e0bca7924a7afdaf5a194630bb2ed1e750",
        "vnd.docker.reference.type": "attestation-manifest"
      },
      "platform": {
        "architecture": "unknown",
        "os": "unknown"
      }
    }
  ]
}