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README.md

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+# 🪞 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