Run the root check before the other checks in order to fail fast if non-root to avoid strange errors. Also auto-start the kubelet if inactive

cmd/kubeadm/app/cmd/init.go

@@ -22,6 +22,7 @@ import (
 	"html/template"
 	"io"
 	"io/ioutil"
+	"os"
 
 	"github.com/renstrom/dedent"
 	"github.com/spf13/cobra"
@@ -183,15 +184,26 @@ func NewInit(cfgPath string, cfg *kubeadmapi.MasterConfiguration, skipPreFlight
 	}
 
 	if !skipPreFlight {
-		fmt.Println("Running pre-flight checks")
-		err := preflight.RunInitMasterChecks(cfg)
-		if err != nil {
+		fmt.Println("[preflight] Running pre-flight checks...")
+
+		// First, check if we're root separately from the other preflight checks and fail fast
+		if err := preflight.RunChecks([]preflight.PreFlightCheck{preflight.IsRootCheck{}}, os.Stderr); err != nil {
+			return nil, &preflight.PreFlightError{Msg: err.Error()}
+		}
+
+		// Then continue with the others...
+		if err := preflight.RunInitMasterChecks(cfg); err != nil {
 			return nil, &preflight.PreFlightError{Msg: err.Error()}
 		}
 	} else {
 		fmt.Println("Skipping pre-flight checks")
 	}
 
+	// Try to start the kubelet service in case it's inactive
+	if err := preflight.TryStartKubelet(); err != nil {
+		return nil, &preflight.PreFlightError{Msg: err.Error()}
+	}
+
 	// validate version argument
 	ver, err := kubeadmutil.KubernetesReleaseVersion(cfg.KubernetesVersion)
 	if err != nil {

cmd/kubeadm/app/cmd/join.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"os"
 
 	"github.com/renstrom/dedent"
 	"github.com/spf13/cobra"
@@ -113,15 +114,26 @@ func NewJoin(cfgPath string, args []string, cfg *kubeadmapi.NodeConfiguration, s
 	}
 
 	if !skipPreFlight {
-		fmt.Println("Running pre-flight checks")
-		err := preflight.RunJoinNodeChecks(cfg)
-		if err != nil {
+		fmt.Println("[preflight] Running pre-flight checks...")
+
+		// First, check if we're root separately from the other preflight checks and fail fast
+		if err := preflight.RunChecks([]preflight.PreFlightCheck{preflight.IsRootCheck{}}, os.Stderr); err != nil {
+			return nil, &preflight.PreFlightError{Msg: err.Error()}
+		}
+
+		// Then continue with the others...
+		if err := preflight.RunJoinNodeChecks(cfg); err != nil {
 			return nil, &preflight.PreFlightError{Msg: err.Error()}
 		}
 	} else {
 		fmt.Println("Skipping pre-flight checks")
 	}
 
+	// Try to start the kubelet service in case it's inactive
+	if err := preflight.TryStartKubelet(); err != nil {
+		return nil, &preflight.PreFlightError{Msg: err.Error()}
+	}
+
 	ok, err := kubeadmutil.UseGivenTokenIfValid(&cfg.Secrets)
 	if !ok {
 		if err != nil {

cmd/kubeadm/app/preflight/checks.go

@@ -51,7 +51,8 @@ type PreFlightCheck interface {
 // detect a supported init system however, all checks are skipped and a warning is
 // returned.
 type ServiceCheck struct {
-	Service string
+	Service       string
+	CheckIfActive bool
 }
 
 func (sc ServiceCheck) Check() (warnings, errors []error) {
@@ -73,7 +74,7 @@ func (sc ServiceCheck) Check() (warnings, errors []error) {
 				sc.Service, sc.Service))
 	}
 
-	if !initSystem.ServiceIsActive(sc.Service) {
+	if sc.CheckIfActive && !initSystem.ServiceIsActive(sc.Service) {
 		errors = append(errors,
 			fmt.Errorf("%s service is not active, please run 'systemctl start %s.service'",
 				sc.Service, sc.Service))
@@ -128,7 +129,7 @@ func (poc PortOpenCheck) Check() (warnings, errors []error) {
 }
 
 // IsRootCheck verifies user is root
-type IsRootCheck struct {}
+type IsRootCheck struct{}
 
 func (irc IsRootCheck) Check() (warnings, errors []error) {
 	errors = []error{}
@@ -260,8 +261,8 @@ func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 		SystemVerificationCheck{},
 		IsRootCheck{},
 		HostnameCheck{},
-		ServiceCheck{Service: "kubelet"},
-		ServiceCheck{Service: "docker"},
+		ServiceCheck{Service: "kubelet", CheckIfActive: false},
+		ServiceCheck{Service: "docker", CheckIfActive: true},
 		FirewalldCheck{ports: []int{int(cfg.API.BindPort), int(cfg.Discovery.BindPort), 10250}},
 		PortOpenCheck{port: int(cfg.API.BindPort)},
 		PortOpenCheck{port: 8080},
@@ -302,8 +303,8 @@ func RunJoinNodeChecks(cfg *kubeadmapi.NodeConfiguration) error {
 		SystemVerificationCheck{},
 		IsRootCheck{},
 		HostnameCheck{},
-		ServiceCheck{Service: "docker"},
-		ServiceCheck{Service: "kubelet"},
+		ServiceCheck{Service: "kubelet", CheckIfActive: false},
+		ServiceCheck{Service: "docker", CheckIfActive: true},
 		PortOpenCheck{port: 10250},
 		HTTPProxyCheck{Proto: "https", Host: cfg.MasterAddresses[0], Port: int(cfg.APIPort)},
 		HTTPProxyCheck{Proto: "http", Host: cfg.MasterAddresses[0], Port: int(cfg.DiscoveryPort)},
@@ -346,3 +347,17 @@ func RunChecks(checks []PreFlightCheck, ww io.Writer) error {
 	}
 	return nil
 }
+
+func TryStartKubelet() error {
+	// If we notice that the kubelet service is inactive, try to start it
+	initSystem, err := initsystem.GetInitSystem()
+	if err != nil {
+		fmt.Println("[preflight] No supported init system detected, won't check if kubelet is running")
+	} else if !initSystem.ServiceIsActive("kubelet") {
+		fmt.Printf("[preflight] Starting the kubelet service by running %q\n", "systemctl start kubelet")
+		if err := initSystem.ServiceStart("kubelet"); err != nil {
+			return fmt.Errorf("Couldn't start the kubelet service. Please start the kubelet service manually and try again.")
+		}
+	}
+	return nil
+}