[v2021.1.x] Backport build-container action

.github/workflows/build-container.yml

@@ -0,0 +1,48 @@
+# Based on the example from https://docs.github.com/en/actions/publishing-packages/publishing-docker-images
+name: Create and publish a Docker image
+
+on:
+  push:
+    branches:
+      - 'main'
+      - 'next'
+      - 'v202[0-9].[0-9].x'
+    tags:
+      - 'v*'
+  pull_request:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}-build
+
+jobs:
+  build-and-push-image:
+    runs-on: ubuntu-22.04
+    permissions: write-all
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Log in to the Container registry
+        uses: docker/login-action@c94ce9fb468520275223c153574b00df6fe4bcc9
+        if: ${{ github.repository_owner == 'freifunk-gluon' && github.event_name == 'push' }}
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@c299e40c65443455700f0fdfc63efafe5b349051
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+      - name: Build and push Docker image
+        uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83
+        with:
+          context: ./contrib/docker
+          push: ${{ github.repository_owner == 'freifunk-gluon' && github.event_name == 'push' }}
+          platforms: linux/amd64,linux/arm64
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

contrib/docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM debian:buster-slim
+FROM debian/eol:buster-slim
 
 ARG DEBIAN_FRONTEND=noninteractive
 RUN apt-get update && apt-get install -y --no-install-recommends \