ci: publish multi-arch operator images

.github/workflows/ci.yaml

@@ -99,23 +99,31 @@ jobs:
     runs-on: ubuntu-latest
     permissions:
       contents: read
+    strategy:
+      fail-fast: false
+      matrix:
+        # The Containerfile cross-compiles, so a non-native architecture still
+        # builds on this amd64 runner without emulation.
+        arch: [amd64, arm64]
+    env:
+      ARCH: ${{ matrix.arch }}
     steps:
       - name: Checkout
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           persist-credentials: false
 
       - name: Build operator image
-        run: make buildimg
+        run: make buildimg IMG="bootc-operator:dev-${ARCH}" PLATFORM="linux/${ARCH}"
 
       - name: Save operator image
-        run: podman save -o operator-image.tar bootc-operator:dev
+        run: podman save -o "operator-image-${ARCH}.tar" "bootc-operator:dev-${ARCH}"
 
       - name: Upload operator image
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
-          name: operator-image
-          path: operator-image.tar
+          name: operator-image-${{ matrix.arch }}
+          path: operator-image-${{ matrix.arch }}.tar
 
   e2e:
     runs-on: ubuntu-latest
@@ -180,10 +188,10 @@ jobs:
       - name: Download operator image
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
-          name: operator-image
+          name: operator-image-amd64
 
       - name: Load operator image
-        run: podman load -i operator-image.tar
+        run: podman load -i operator-image-amd64.tar
 
       - name: Fix registries configuration
         run: |
@@ -195,7 +203,7 @@ jobs:
         run: make start-bink
 
       - name: Deploy to bink cluster
-        run: make deploy-bink
+        run: make deploy-bink IMG=bootc-operator:dev-amd64
 
       - name: Gather deploy logs
         if: failure()
@@ -222,13 +230,29 @@ jobs:
     env:
       IMAGE: ghcr.io/${{ github.repository }}
     steps:
-      - name: Download operator image
+      - name: Download operator images
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with:
-          name: operator-image
+          pattern: operator-image-*
+          merge-multiple: true
 
-      - name: Load operator image
-        run: podman load -i operator-image.tar
+      - name: Assemble manifest list
+        run: |
+          shopt -s failglob
+          refs=()
+          for tar in operator-image-*.tar; do
+            arch="${tar#operator-image-}"
+            arch="${arch%.tar}"
+            podman load -i "$tar"
+            refs+=("containers-storage:localhost/bootc-operator:dev-$arch")
+          done
+          # Guard against a missing artifact silently publishing a partial
+          # manifest list, which would leave some nodes unable to pull.
+          if [[ "${#refs[@]}" -lt 2 ]]; then
+            echo "expected at least 2 architectures, got ${#refs[@]}" >&2
+            exit 1
+          fi
+          podman manifest create bootc-operator:dev "${refs[@]}"
 
       - name: Push to GHCR
         env:
@@ -239,13 +263,20 @@ jobs:
           REF_NAME: ${{ github.ref_name }}
         run: |
           podman login -u "${ACTOR}" -p "${GH_TOKEN}" ghcr.io
-          podman push bootc-operator:dev "${IMAGE}":dev
-          podman push bootc-operator:dev "${IMAGE}":"${SHA}"
+          tags=(dev "${SHA}")
 
           if [[ "${REF}" == refs/tags/v* ]]; then
-            podman push bootc-operator:dev "${IMAGE}":"${REF_NAME}"
+            tags+=("${REF_NAME}")
           fi
 
           if [[ "${REF}" == refs/heads/main ]]; then
-            podman push bootc-operator:dev "${IMAGE}":latest
+            tags+=(latest)
           fi
+
+          # v2s2 keeps the per-architecture manifests in the same format as
+          # the images published before this became a manifest list, so the
+          # only change downstream sees is the added list layer.
+          for tag in "${tags[@]}"; do
+            podman manifest push --all --format v2s2 \
+              bootc-operator:dev "docker://${IMAGE}:${tag}"
+          done

CONTRIBUTING.md

@@ -78,11 +78,26 @@ make deploy-bink BINK_CLUSTER_NAME=dev
 ```shell
 make build           # Build all binaries (manager + daemon) to ./bin/
 make buildimg        # Build the container image (default: bootc-operator:dev)
+make buildimg-all    # Build a multi-arch manifest list (linux/amd64, linux/arm64)
 ```
 
 The `bootc-operator` container image contains both the controller and daemon
 binaries.
 
+Released images are manifest lists covering `linux/amd64` and `linux/arm64`.
+Both binaries are pure Go, so the Containerfile cross-compiles them for the
+target architecture instead of emulating the toolchain; building for a
+non-native architecture therefore costs about the same as a native build and
+needs no qemu setup. To build a single non-native image, pass `PLATFORM`:
+
+```shell
+make buildimg PLATFORM=linux/arm64
+```
+
+Note that the e2e suite remains amd64-only, because the
+[bink](https://github.com/bootc-dev/bink) node images it boots are published
+for amd64 alone.
+
 After modifying API types in `api/`, regenerate CRDs and code:
 
 ```shell

Containerfile

@@ -1,4 +1,4 @@
-FROM quay.io/fedora/fedora-minimal:44 AS buildroot
+FROM --platform=$BUILDPLATFORM quay.io/fedora/fedora-minimal:44 AS buildroot
 ARG DNF_FLAGS="-y --setopt=install_weak_deps=False"
 RUN --mount=type=cache,id=dnf,target=/var/cache/libdnf5 \
     dnf install ${DNF_FLAGS} golang
@@ -9,10 +9,15 @@ COPY go.mod go.sum ./
 RUN --mount=type=cache,id=gomod,target=/root/go/pkg/mod \
     go mod download
 COPY . .
+# The buildroot stage always runs on the build host's architecture, so cross
+# compile via TARGETARCH rather than emulating the Go toolchain. Both binaries
+# are pure Go, hence CGO_ENABLED=0. The Go build cache is content addressed and
+# keyed on the target, so sharing it across architectures is safe.
+ARG TARGETARCH
 RUN --mount=type=cache,id=gomod,target=/root/go/pkg/mod \
     --mount=type=cache,id=gobuild,target=/root/.cache/go-build \
-    go build -o manager ./cmd/controller/ && \
-    go build -o daemon ./cmd/daemon/
+    CGO_ENABLED=0 GOARCH=${TARGETARCH} go build -o manager ./cmd/controller/ && \
+    CGO_ENABLED=0 GOARCH=${TARGETARCH} go build -o daemon ./cmd/daemon/
 
 FROM quay.io/fedora/fedora-minimal:44
 COPY --from=builder /workspace/manager /workspace/daemon /usr/local/bin/

Makefile

@@ -1,6 +1,9 @@
 # Image URL to use all building/pushing image targets
 IMG ?= bootc-operator:dev
 CONTAINER_TOOL ?= podman
+# Architectures published by buildimg-all. Both binaries are pure Go, so the
+# Containerfile cross-compiles rather than emulating the toolchain.
+PLATFORMS ?= linux/amd64,linux/arm64
 # Bink cluster settings. deploy-bink and e2e share the same cluster by default.
 # To use a separate dev cluster: make deploy-bink BINK_CLUSTER_NAME=dev
 BINK_CLUSTER_NAME ?= e2e
@@ -89,8 +92,12 @@ build-daemon: ## Build daemon binary.
 	go build -o bin/daemon ./cmd/daemon/
 
 .PHONY: buildimg
-buildimg: ## Build container image.
-	$(CONTAINER_TOOL) build -t $(IMG) .
+buildimg: ## Build container image. PLATFORM=linux/arm64 cross-builds for another arch.
+	$(CONTAINER_TOOL) build $(if $(PLATFORM),--platform $(PLATFORM)) -t $(IMG) .
+
+.PHONY: buildimg-all
+buildimg-all: ## Build a multi-arch manifest list image (override PLATFORMS to change).
+	$(CONTAINER_TOOL) build --platform $(PLATFORMS) --manifest $(IMG) .
 
 .PHONY: build-update-image
 build-update-image: ## Build a derived node image for update testing and push to bink registry.