Multi-Arch Docker Builds with Github Actions

In this tutorial we will be using github actions to build multi-architecture docker builds.

End Result

We will keep it basic as we will build busybox container images for x86_64 as well as aarch64 using github actions.

Docker Container Image

As mentioned, we will have a basic demonstration, where we are just referencing a upstream image that supports both x86_64 and aarch64 container images, then we are just adding a couple of labels and then we will push the image.

Our Dockerfile in multi-arch-docker-builds/Dockerfile:

Dockerfile

FROM busybox:stable

ARG OS_ARCH=x86_64
ARG APP_VERSION="1.0"
ENV OS_ARCH=$OS_ARCH

LABEL "dev.ruan.ci.arch"="$OS_ARCH"
LABEL "dev.ruan.ci.version"="$APP_VERSION"

Github Actions Workflow

In our github actions workflow .github/workflows/multi-arch-docker-builds.yml:

multi-arch-docker-builds.yml

name: CI - Busybox

on:
  push:
    branches: [ main ]
    paths:
      - multi-arch-docker-builds/**

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v2

    - name: Set tag
      id: vars
      run: echo "tag=$(cat multi-arch-docker-builds/Dockerfile | grep 'FROM' | cut -d ':' -f2)" >> $GITHUB_OUTPUT

    - name: Set up Docker Buildx
      uses: docker/setup-buildx-action@v3

    - name: Set up QEMU
      uses: docker/setup-qemu-action@v3

    - name: Login to DockerHub
      uses: docker/login-action@v1
      with:
        username: ${{ secrets.DOCKERHUB_USER }}
        password: ${{ secrets.DOCKERHUB_PASSWORD }}

    - name: Build and push
      id: docker_build
      uses: docker/build-push-action@v2
      with:
        context: ./multi-arch-docker-builds
        file: ./multi-arch-docker-builds/Dockerfile
        push: true
        platforms: "linux/arm64,linux/amd64"
        build-args: |
          APP_VERSION=1.0.1
        tags: |
          ${{ secrets.DOCKERHUB_USER }}/busybox:${{ steps.vars.outputs.tag }}
          ${{ secrets.DOCKERHUB_USER }}/busybox:latest

Let's go through this workflow step-by-step:

Trigger:

We have defined the name of our workflow "CI - Busybox".
Trigger Condition: it will trigger on the main branch only if changes are detected in multi-arch-docker-builds/ directory.

Jobs:

We are defining the ubuntu-latest GitHub hosted runner.

Steps in Build Jobs:

Checkout the code.
Set the tag from the tag that is defined in the upstream image in the Dockerfile.
Set up docker buildx for extended build capabilities with BuildKit, including support for multiple architectures.
Sets up QEMU on the runner to support open-source machine emulator in order to run multi-arch.
Login to Docker Hub.
Builds and push container images to Docker Hub.

For this demonstration the images was pushed to :

https://hub.docker.com/r/ruanbekker/busybox/tags?page=&page_size=&ordering=&name=stable

Which we can see from this screenshot we have succesfully published our tag that supports both architectures:

Thank You

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