Fix MTU configuration for dockerd (#421)

Resolves #393

acceptance/testdata/runnerdeploy.yaml

@@ -7,3 +7,14 @@ spec:
   template:
     spec:
       repository: mumoshu/actions-runner-controller-ci
+      #
+      # dockerd within runner container
+      #
+      ## Replace `mumoshu/actions-runner-dind:dev` with your dind image
+      #dockerdWithinRunnerContainer: true
+      #image: mumoshu/actions-runner-dind:dev
+
+      #
+      # Set the MTU used by dockerd-managed network interfaces (including docker-build)
+      #
+      #dockerMTU: 1450

controllers/runner_controller.go

@@ -703,6 +703,7 @@ func (r *RunnerReconciler) newPod(runner v1alpha1.Runner) (corev1.Pod, error) {
 		pod.Spec.Containers = append(pod.Spec.Containers, corev1.Container{
 			Name:  "docker",
 			Image: r.DockerImage,
+			Args:  []string{"dockerd"},
 			VolumeMounts: []corev1.VolumeMount{
 				{
 					Name:      "work",
@@ -731,11 +732,17 @@ func (r *RunnerReconciler) newPod(runner v1alpha1.Runner) (corev1.Pod, error) {
 
 		if mtu := runner.Spec.DockerMTU; mtu != nil {
 			pod.Spec.Containers[1].Env = append(pod.Spec.Containers[1].Env, []corev1.EnvVar{
+				// See https://docs.docker.com/engine/security/rootless/
 				{
 					Name:  "DOCKERD_ROOTLESS_ROOTLESSKIT_MTU",
 					Value: fmt.Sprintf("%d", *runner.Spec.DockerMTU),
 				},
 			}...)
+
+			pod.Spec.Containers[1].Args = append(pod.Spec.Containers[1].Args,
+				"--mtu",
+				fmt.Sprintf("%d", *runner.Spec.DockerMTU),
+			)
 		}
 
 	}

runner/startup.sh

@@ -17,6 +17,34 @@ function wait_for_process () {
     return 0
 }
 
+sudo /bin/bash <<SCRIPT
+mkdir -p /etc/docker
+
+cat <<EOS > /etc/docker/daemon.json
+{
+EOS
+
+if [ -n "${MTU}" ]; then
+cat <<EOS >> /etc/docker/daemon.json
+  "mtu": ${MTU}
+EOS
+# See https://docs.docker.com/engine/security/rootless/
+echo "environment=DOCKERD_ROOTLESS_ROOTLESSKIT_MTU=${MTU}" >> /etc/supervisor/conf.d/dockerd.conf
+fi
+
+cat <<EOS >> /etc/docker/daemon.json
+}
+EOS
+SCRIPT
+
+INFO "Using /etc/docker/daemon.json with the following content"
+
+cat /etc/docker/daemon.json
+
+INFO "Using /etc/supervisor/conf.d/dockerd.conf with the following content"
+
+cat /etc/supervisor/conf.d/dockerd.conf
+
 INFO "Starting supervisor"
 sudo /usr/bin/supervisord -n >> /dev/null 2>&1 &
 
@@ -27,6 +55,8 @@ for process in "${processes[@]}"; do
     wait_for_process "$process"
     if [ $? -ne 0 ]; then
         ERROR "$process is not running after max time"
+        ERROR "Dumping /var/log/dockerd.err.log to help investigation"
+        cat /var/log/dockerd.err.log
         exit 1
     else 
         INFO "$process is running"