docs/build/ci/github-actions/multi-platform.md

title	keywords
Multi-platform image with GitHub Actions	ci, github actions, gha, buildkit, buildx, multi-platform

You can build multi-platform images using the platforms option, as shown in the following example:

Note

• For a list of available platforms, see the Docker Setup Buildx{:target="blank" rel="noopener" class=""} action.
• If you want support for more platforms, you can use QEMU with the Docker Setup QEMU{:target="blank" rel="noopener" class=""} action.

{% raw %}

name: ci

on:
  push:
    branches:
      - "main"

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v3
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v2
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Build and push
        uses: docker/build-push-action@v4
        with:
          context: .
          platforms: linux/amd64,linux/arm64
          push: true
          tags: user/app:latest

{% endraw %}

Distribute build across multiple runners

In the previous example, each platform is built on the same runner which can take a long time depending on the number of platforms and your Dockerfile.

To solve this issue you can use a matrix strategy to distribute the build for each platform across multiple runners and create manifest list using the buildx imagetools create command.

The following workflow will build the image for each platform on a dedicated runner using a matrix strategy and push by digest. Then, the merge job will create a manifest list and push it to Docker Hub.

This example also uses the metadata action to set tags and labels.

{% raw %}

name: ci

on:
  push:
    branches:
      - "main"

env:
  REGISTRY_IMAGE: user/app

jobs:
  build:
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        platform:
          - linux/amd64
          - linux/arm/v6
          - linux/arm/v7
          - linux/arm64
    steps:
      -
        name: Checkout
        uses: actions/checkout@v3
      -
        name: Docker meta
        id: meta
        uses: docker/metadata-action@v4
        with:
          images: ${{ env.REGISTRY_IMAGE }}
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v2
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Build and push by digest
        id: build
        uses: docker/build-push-action@v4
        with:
          context: .
          platforms: ${{ matrix.platform }}
          labels: ${{ steps.meta.outputs.labels }}
          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true,push=true
      -
        name: Export digest
        run: |
          mkdir -p /tmp/digests
          digest="${{ steps.build.outputs.digest }}"
          touch "/tmp/digests/${digest#sha256:}"          
      -
        name: Upload digest
        uses: actions/upload-artifact@v3
        with:
          name: digests
          path: /tmp/digests/*
          if-no-files-found: error
          retention-days: 1
  
  merge:
    runs-on: ubuntu-latest
    needs:
      - build
    steps:
      -
        name: Download digests
        uses: actions/download-artifact@v3
        with:
          name: digests
          path: /tmp/digests
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Docker meta
        id: meta
        uses: docker/metadata-action@v4
        with:
          images: ${{ env.REGISTRY_IMAGE }}
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Create manifest list and push
        working-directory: /tmp/digests
        run: |
          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
            $(printf '${{ env.REGISTRY_IMAGE }}@sha256:%s ' *)          
      -
        name: Inspect image
        run: |
          docker buildx imagetools inspect ${{ env.REGISTRY_IMAGE }}:${{ steps.meta.outputs.version }}          

{% endraw %}