Only restart docker service if container runtime is docker (#3426)

* Only restart docker service if container runtime is docker

Only allow the buildroot provisioner to restart docker if the container
runtime is docker. This change should fix the bug in #3424, since now
docker will not be restarted if the container runtime is containerd.

* Added files to fix FileContent--proc-sys-net-bridge-bridge-nf-call-iptables precheck error

From this issue: https://github.com/kubernetes/kubeadm/issues/1062
these files need to be added to prevent this precheck error (which occurs when running any container runtime that isn't docker).

Also, save the machine config on the user's filesystem earlier so that the buildprovisioner can access it.

cmd/minikube/cmd/start.go

@@ -161,6 +161,15 @@ func runStart(cmd *cobra.Command, args []string) {
 		GPU:                 viper.GetBool(gpu),
 	}
 
+	// Write profile cluster configuration to file
+	clusterConfig := cfg.Config{
+		MachineConfig: config,
+	}
+
+	if err := saveConfig(clusterConfig); err != nil {
+		glog.Errorln("Error saving profile cluster configuration: ", err)
+	}
+
 	fmt.Printf("Starting local Kubernetes %s cluster...\n", viper.GetString(kubernetesVersion))
 	fmt.Println("Starting VM...")
 	var host *host.Host
@@ -235,7 +244,7 @@ func runStart(cmd *cobra.Command, args []string) {
 	}
 
 	// Write profile cluster configuration to file
-	clusterConfig := cfg.Config{
+	clusterConfig = cfg.Config{
 		MachineConfig:    config,
 		KubernetesConfig: kubernetesConfig,
 	}

pkg/minikube/bootstrapper/kubeadm/kubeadm.go

@@ -118,7 +118,18 @@ func (k *KubeadmBootstrapper) StartCluster(k8s config.KubernetesConfig) error {
 	preflights := constants.Preflights
 	if k8s.ContainerRuntime != "" {
 		preflights = constants.AlternateRuntimePreflights
+		out, err := k.c.CombinedOutput("sudo modprobe br_netfilter")
+		if err != nil {
+			glog.Infoln(out)
+			return errors.Wrap(err, "sudo modprobe br_netfilter")
+		}
+		out, err = k.c.CombinedOutput("sudo sh -c \"echo '1' > /proc/sys/net/ipv4/ip_forward\"")
+		if err != nil {
+			glog.Infoln(out)
+			return errors.Wrap(err, "creating /proc/sys/net/ipv4/ip_forward")
+		}
 	}
+
 	templateContext := struct {
 		KubeadmConfigFile   string
 		SkipPreflightChecks bool

pkg/provision/buildroot.go

@@ -37,6 +37,7 @@ import (
 	"github.com/pkg/errors"
 	"k8s.io/minikube/pkg/minikube/assets"
 	"k8s.io/minikube/pkg/minikube/bootstrapper"
+	"k8s.io/minikube/pkg/minikube/config"
 	"k8s.io/minikube/pkg/minikube/sshutil"
 	"k8s.io/minikube/pkg/util"
 )
@@ -288,6 +289,15 @@ func configureAuth(p *BuildrootProvisioner) error {
 		}
 	}
 
+	config, err := config.Load()
+	if err != nil {
+		return errors.Wrap(err, "getting cluster config")
+	}
+
+	if config.MachineConfig.ContainerRuntime != "" {
+		return nil
+	}
+
 	dockerCfg, err := p.GenerateDockerOptions(engine.DefaultPort)
 	if err != nil {
 		return errors.Wrap(err, "generating docker options")