Bits of .NET

🐳 One Build, All Architectures

Intel Mac, Apple Silicon, ARM servers, AMD servers — different architectures. Docker Buildx builds for all from a single machine.

🔧 Setup Buildx

# Create new builder instance (supports multiple platforms)
docker buildx create --name multiarch --use

# Bootstrap builder
docker buildx inspect --bootstrap

# Verify platforms
docker buildx ls

# Build multi-platform image
docker buildx build \
  --platform linux/amd64,linux/arm64,linux/arm/v7 \
  -t myapp:latest \
  --push .

🎯 Dockerfile Best Practices

FROM --platform=$BUILDPLATFORM golang:1.21 AS builder
ARG TARGETOS TARGETARCH
WORKDIR /app
COPY . .
RUN GOOS=$TARGETOS GOARCH=$TARGETARCH go build -o app

FROM alpine:latest
COPY --from=builder /app/app /app
CMD ["/app"]

# --platform=$BUILDPLATFORM: use native platform for build stage
# TARGETOS/TARGETARCH: passed automatically by Buildx

✅ GitHub Actions Integration

name: Build Multi-Platform

on:
  push:
    branches: [main]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - 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 DockerHub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKER_TOKEN }}
      
      - name: Build and push
        uses: docker/build-push-action@v4
        with:
          platforms: linux/amd64,linux/arm64
          push: true
          tags: user/myapp:latest

💡 Tips

• Use QEMU for emulation (slower) or native builders (faster)
• Combine with GitHub Actions self-hosted runners for each arch
• Test each platform before pushing multi-arch manifest
• Use –provenance=true for SBOM attestation