# 🪞 QEMU binfmt Mirror

A mirror of [`tonistiigi/binfmt`](https://github.com/tonistiigi/binfmt) hosted on a self-hosted Gitea Container Registry to speed up multi-platform Docker builds in CI/CD pipelines.

## Why?

When building Docker images for multiple platforms (e.g. `linux/amd64` + `linux/arm64`) on an `amd64`-only runner, QEMU emulation is required. The `setup-qemu-action` pulls `tonistiigi/binfmt` from Docker Hub on every run — which can take **4–5 minutes** depending on network conditions.

By mirroring the image locally, the pull happens at LAN speed and reduces this step to a **few seconds**.

## Usage

In your Gitea Actions workflow, point `setup-qemu-action` to this mirror:

```yaml
- name: Set up QEMU
  uses: docker/setup-qemu-action@v3
  with:
    image: git.mrunk.de/mrunknownde/binfmt:latest
```

Full example workflow with multi-platform build:

```yaml
- uses: actions/checkout@v4

- name: Set up QEMU
  uses: docker/setup-qemu-action@v3
  with:
    image: git.mrunk.de/mrunknownde/binfmt:latest

- name: Set up Docker Buildx
  uses: docker/setup-buildx-action@v3
  with:
    cache-binary: true

- name: Build and push
  uses: docker/build-push-action@v5
  with:
    platforms: linux/amd64,linux/arm64
    push: true
    tags: your-registry/your-image:latest
```

## Keeping the Mirror Up to Date

This repo includes an automated workflow that re-mirrors the image every Monday at 03:00 UTC.

To trigger a manual update:

1. Go to **Actions** in this repository
2. Select **Mirror QEMU Image**
3. Click **Run workflow**

## Mirror Workflow

```yaml
name: Mirror QEMU Image

on:
  schedule:
    - cron: '0 3 * * 1'
  workflow_dispatch:

jobs:
  mirror:
    runs-on: ubuntu-latest
    steps:
      - uses: docker/login-action@v3
        with:
          registry: git.mrunk.de
          username: ${{ secrets.REGISTRY_USERNAME }}
          password: ${{ secrets.REGISTRY_TOKEN }}

      - name: Mirror tonistiigi/binfmt
        run: |
          docker pull tonistiigi/binfmt:latest
          docker tag tonistiigi/binfmt:latest git.mrunk.de/mrunknownde/binfmt:latest
          docker push git.mrunk.de/mrunknownde/binfmt:latest
```

## Credits

Original image: [`tonistiigi/binfmt`](https://github.com/tonistiigi/binfmt) — MIT License