The BuildKit Cache Dance: save RUN --mount=type=cache caches on GitHub Actions

The BuildKit Cache Dance allows saving RUN --mount=type=cache caches on GitHub Actions.

Use cases:

• apt-get (/var/cache/apt, /var/lib/apt)
• Go (/root/.cache/go-build)
• etc.

This reproducible-containers/buildkit-cache-dance action was forked from overmindtech/buildkit-cache-dance (archived on September 2023). This action be used for "non-reproducible" containers too.

Examples

apt-get

Dockerfile:

FROM ubuntu:22.04
ENV DEBIAN_FRONTEND=noninteractive
RUN \
  --mount=type=cache,target=/var/cache/apt,sharing=locked \
  --mount=type=cache,target=/var/lib/apt,sharing=locked \
  rm -f /etc/apt/apt.conf.d/docker-clean && \
  echo 'Binary::apt::APT::Keep-Downloaded-Packages "true";' >/etc/apt/apt.conf.d/keep-cache && \
  apt-get update && \
  apt-get install -y gcc

Action:

---
name: Build
on: push

jobs:
  build:
    name: Build
    runs-on: ubuntu-22.04
    steps:
      - uses: actions/checkout@v4
      - uses: docker/setup-buildx-action@v3
      - uses: docker/metadata-action@v5
        id: meta
        with:
          images: YOUR_IMAGE
      - name: Cache var-cache-apt
        uses: actions/cache@v3
        with:
          path: var-cache-apt
          key: var-cache-apt-${{ hashFiles('Dockerfile') }}
      - name: Cache var-lib-apt
        uses: actions/cache@v3
        with:
          path: var-lib-apt
          key: var-lib-apt-${{ hashFiles('Dockerfile') }}
      - name: inject var-cache-apt into docker
        uses: reproducible-containers/[email protected]
        with:
          cache-source: var-cache-apt
          cache-target: /var/cache/apt
      - name: inject var-lib-apt into docker
        uses: reproducible-containers/[email protected]
        with:
          cache-source: var-lib-apt
          cache-target: /var/lib/apt
      - name: Build and push
        uses: docker/build-push-action@v5
        with:
          context: .
          cache-from: type=gha
          cache-to: type=gha,mode=max
          file: Dockerfile
          push: ${{ github.event_name != 'pull_request' }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}

Real-world examples:

• https://github.com/rootless-containers/slirp4netns/blob/v1.2.2/.github/workflows/release.yaml#L18-L36
• https://github.com/containers/fuse-overlayfs/blob/40e0f3c/.github/workflows/release.yaml#L17-L36

Releases

v1

v1 follows the original design of overmindtech/buildkit-cache-dance.

v1 is composed of two actions:

• reproducible-containers/buildkit-cache-dance/[email protected]
• reproducible-containers/buildkit-cache-dance/[email protected]

See the releases/v1 branch.

v2

v2 is composed of the single reproducible-containers/buildkit-cache-dance action.

Acknowledgement

• Thanks to Alexander Pravdin for the basic idea in this comment.
• Thanks to the authors of the original overmindtech/buildkit-cache-dance.