ci: native arm64 runners (untested, isolated from action-plan branch)

.github/workflows/armbian-builder.yaml

@@ -283,7 +283,14 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    # Native arm64 runner -- the images we build are arm64, and Packer's
+    # arm-image plugin skips its QEMU/binfmt chroot steps entirely when
+    # image_arch (set in dpx-buttonode.pkr.hcl) matches the host's actual
+    # runtime arch (pkg/builder/builder.go: `!ImageArch.IsNative()`). On
+    # ubuntu-latest (x86_64), every apt-get/dpkg inside the chroot ran
+    # through qemu-aarch64-static emulation, which is commonly 5-10x
+    # slower than native for that kind of CPU-bound work.
+    runs-on: ubuntu-24.04-arm
     permissions:
       contents: read
     outputs:
@@ -294,7 +301,15 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      # ARM emulation is required to chroot into the ARM64 Armbian image
+      # Still needed even on a native arm64 runner: the plugin's Prepare()
+      # step unconditionally resolves a qemu_binary path via exec.LookPath
+      # regardless of whether it'll actually be used later -- only its
+      # separate Run()-time IsNative() check decides whether QEMU is
+      # actually invoked for the chroot. Without this installed, Prepare()
+      # falls back to an "embedded qemu" feature that's amd64-only and
+      # fails outright on arm64 (confirmed: "embedded qemu is not
+      # available - currently, embedded qemu is only available for linux
+      # amd64"). This is just a fast package install, not the slow part.
       - name: Install QEMU user-static
         run: sudo apt-get update -q && sudo apt-get install -y qemu-user-static
 

.github/workflows/raspios-builder.yaml

@@ -41,7 +41,12 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    # See armbian-builder.yaml's build job for why: native arm64 runner
+    # lets Packer's arm-image plugin skip QEMU/binfmt entirely
+    # (image_arch in dpx-buttonode.pkr.hcl matches the host arch), instead
+    # of emulating every chroot apt-get/dpkg call via qemu-aarch64-static
+    # on an x86_64 runner.
+    runs-on: ubuntu-24.04-arm
     permissions:
       contents: read
     outputs:
@@ -52,8 +57,9 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      # ARM emulation is required to chroot into the ARM64 image, same as
-      # the Armbian pipeline -- unrelated to which OS built the base image.
+      # Still needed on a native arm64 runner -- see armbian-builder.yaml's
+      # build job for why (Prepare()-time qemu_binary resolution is
+      # unconditional, only actual usage is skipped on native arch).
       - name: Install QEMU user-static
         run: sudo apt-get update -q && sudo apt-get install -y qemu-user-static
 

dpx-buttonode.pkr.hcl

@@ -73,6 +73,7 @@ source "arm-image" "base" {
   iso_url           = var.url
   target_image_size = var.variant == "full" ? 8000000000 : 5000000000
   output_filename   = "output-dpx-buttonode/dpx-buttonode.img"
+  image_arch      = "arm64"
   qemu_binary     = "qemu-aarch64-static"
   image_mounts    = var.image_mounts