feat(runner): provide Docker before workflow steps

.gitea/workflows/vm-kind-smoke.yml

@@ -7,64 +7,21 @@ on:
 
 jobs:
   kind:
-    runs-on: [self-hosted, vm-dev]
+    runs-on: [self-hosted, vm]
     steps:
-      - name: Start job-local Docker
+      - name: Prepare nested kubelet device
         shell: bash
         run: |
           set -euo pipefail
           if [[ ! -e /dev/kmsg ]]; then
             sudo mknod /dev/kmsg c 1 11
           fi
-          sudo install -d /var/lib/docker
-          sudo truncate -s 20G /tmp/docker-data.img
-          sudo mkfs.ext4 -F /tmp/docker-data.img
-          if [[ ! -e /dev/loop-control ]]; then
-            sudo mknod /dev/loop-control c 10 237
-          fi
-          for minor in {0..7}; do
-            if [[ ! -e "/dev/loop${minor}" ]]; then
-              sudo mknod "/dev/loop${minor}" b 7 "$minor"
-            fi
-          done
-          loop_device=$(sudo losetup --find --show /tmp/docker-data.img)
-          sudo mount "$loop_device" /var/lib/docker
-          findmnt /var/lib/docker
-
-          # A nested systemd needs a domain cgroup namespace. This is the
-          # cgroup v2 nesting initialization performed by the official DinD
-          # entrypoint, kept here because the shared runner image deliberately
-          # does not carry a second DinD-specific entrypoint.
-          if [[ -f /sys/fs/cgroup/cgroup.controllers ]]; then
-            sudo sh -c '
-              mkdir -p /sys/fs/cgroup/init
-              while read -r pid; do
-                printf "%s\n" "$pid" \
-                  >/sys/fs/cgroup/init/cgroup.procs 2>/dev/null || true
-              done </sys/fs/cgroup/cgroup.procs
-              sed -e "s/ / +/g" -e "s/^/+/" \
-                /sys/fs/cgroup/cgroup.controllers \
-                >/sys/fs/cgroup/cgroup.subtree_control
-            '
-          fi
-
-          sudo nohup dockerd \
-            --host=unix:///var/run/docker.sock \
-            --storage-driver=overlay2 \
-            >/tmp/dockerd.log 2>&1 &
-          for _ in {1..60}; do
-            if docker info >/dev/null 2>&1; then
-              exit 0
-            fi
-            sleep 1
-          done
-          cat /tmp/dockerd.log
-          exit 1
 
       - name: Verify Docker
         shell: bash
         run: |
           set -euo pipefail
+          findmnt /var/lib/docker
           docker info
           echo '### runner cgroup'
           cat /proc/self/cgroup