Merge pull request #69366 from rosti/cri-auto-detect

cmd/kubeadm/app/apis/kubeadm/v1alpha3/defaults.go

@@ -68,7 +68,6 @@ func addDefaultingFuncs(scheme *runtime.Scheme) error {
 // SetDefaults_InitConfiguration assigns default values for the InitConfiguration
 func SetDefaults_InitConfiguration(obj *InitConfiguration) {
 	SetDefaults_ClusterConfiguration(&obj.ClusterConfiguration)
-	SetDefaults_NodeRegistrationOptions(&obj.NodeRegistration)
 	SetDefaults_BootstrapTokens(obj)
 	SetDefaults_APIEndpoint(&obj.APIEndpoint)
 }
@@ -139,16 +138,9 @@ func SetDefaults_JoinConfiguration(obj *JoinConfiguration) {
 		}
 	}
 
-	SetDefaults_NodeRegistrationOptions(&obj.NodeRegistration)
 	SetDefaults_APIEndpoint(&obj.APIEndpoint)
 }
 
-func SetDefaults_NodeRegistrationOptions(obj *NodeRegistrationOptions) {
-	if obj.CRISocket == "" {
-		obj.CRISocket = DefaultCRISocket
-	}
-}
-
 // SetDefaults_AuditPolicyConfiguration sets default values for the AuditPolicyConfiguration
 func SetDefaults_AuditPolicyConfiguration(obj *ClusterConfiguration) {
 	if obj.AuditPolicyConfiguration.LogDir == "" {

cmd/kubeadm/app/apis/kubeadm/v1alpha3/defaults_unix.go

@@ -21,8 +21,4 @@ package v1alpha3
 const (
 	// DefaultCACertPath defines default location of CA certificate on Linux
 	DefaultCACertPath = "/etc/kubernetes/pki/ca.crt"
-	// DefaultUrlScheme defines default socket url prefix
-	DefaultUrlScheme = "unix"
-	// DefaultCRISocket defines the default cri socket
-	DefaultCRISocket = "/var/run/dockershim.sock"
 )

cmd/kubeadm/app/apis/kubeadm/v1alpha3/defaults_windows.go

@@ -21,8 +21,4 @@ package v1alpha3
 const (
 	// DefaultCACertPath defines default location of CA certificate on Windows
 	DefaultCACertPath = "C:/etc/kubernetes/pki/ca.crt"
-	// DefaultUrlScheme defines default socket url prefix
-	DefaultUrlScheme = "tcp"
-	// DefaultCRISocket defines the default cri socket
-	DefaultCRISocket = "tcp://localhost:2375"
 )

cmd/kubeadm/app/apis/kubeadm/v1alpha3/zz_generated.defaults.go

@@ -49,12 +49,10 @@ func SetObjectDefaults_InitConfiguration(in *InitConfiguration) {
 		a := &in.BootstrapTokens[i]
 		SetDefaults_BootstrapToken(a)
 	}
-	SetDefaults_NodeRegistrationOptions(&in.NodeRegistration)
 	SetDefaults_APIEndpoint(&in.APIEndpoint)
 }
 
 func SetObjectDefaults_JoinConfiguration(in *JoinConfiguration) {
 	SetDefaults_JoinConfiguration(in)
-	SetDefaults_NodeRegistrationOptions(&in.NodeRegistration)
 	SetDefaults_APIEndpoint(&in.APIEndpoint)
 }

cmd/kubeadm/app/apis/kubeadm/v1beta1/defaults.go

@@ -68,7 +68,6 @@ func addDefaultingFuncs(scheme *runtime.Scheme) error {
 // SetDefaults_InitConfiguration assigns default values for the InitConfiguration
 func SetDefaults_InitConfiguration(obj *InitConfiguration) {
 	SetDefaults_ClusterConfiguration(&obj.ClusterConfiguration)
-	SetDefaults_NodeRegistrationOptions(&obj.NodeRegistration)
 	SetDefaults_BootstrapTokens(obj)
 	SetDefaults_APIEndpoint(&obj.LocalAPIEndpoint)
 }
@@ -138,17 +137,10 @@ func SetDefaults_JoinConfiguration(obj *JoinConfiguration) {
 		obj.CACertPath = DefaultCACertPath
 	}
 
-	SetDefaults_NodeRegistrationOptions(&obj.NodeRegistration)
 	SetDefaults_JoinControlPlane(obj.ControlPlane)
 	SetDefaults_Discovery(&obj.Discovery)
 }
 
-func SetDefaults_NodeRegistrationOptions(obj *NodeRegistrationOptions) {
-	if obj.CRISocket == "" {
-		obj.CRISocket = DefaultCRISocket
-	}
-}
-
 func SetDefaults_JoinControlPlane(obj *JoinControlPlane) {
 	if obj != nil {
 		SetDefaults_APIEndpoint(&obj.LocalAPIEndpoint)

cmd/kubeadm/app/apis/kubeadm/v1beta1/defaults_unix.go

@@ -23,6 +23,4 @@ const (
 	DefaultCACertPath = "/etc/kubernetes/pki/ca.crt"
 	// DefaultUrlScheme defines default socket url prefix
 	DefaultUrlScheme = "unix"
-	// DefaultCRISocket defines the default cri socket
-	DefaultCRISocket = "/var/run/dockershim.sock"
 )

cmd/kubeadm/app/apis/kubeadm/v1beta1/defaults_windows.go

@@ -23,6 +23,4 @@ const (
 	DefaultCACertPath = "C:/etc/kubernetes/pki/ca.crt"
 	// DefaultUrlScheme defines default socket url prefix
 	DefaultUrlScheme = "tcp"
-	// DefaultCRISocket defines the default cri socket
-	DefaultCRISocket = "tcp://localhost:2375"
 )

cmd/kubeadm/app/apis/kubeadm/v1beta1/zz_generated.defaults.go

@@ -50,13 +50,11 @@ func SetObjectDefaults_InitConfiguration(in *InitConfiguration) {
 		a := &in.BootstrapTokens[i]
 		SetDefaults_BootstrapToken(a)
 	}
-	SetDefaults_NodeRegistrationOptions(&in.NodeRegistration)
 	SetDefaults_APIEndpoint(&in.LocalAPIEndpoint)
 }
 
 func SetObjectDefaults_JoinConfiguration(in *JoinConfiguration) {
 	SetDefaults_JoinConfiguration(in)
-	SetDefaults_NodeRegistrationOptions(&in.NodeRegistration)
 	SetDefaults_Discovery(&in.Discovery)
 	if in.Discovery.File != nil {
 		SetDefaults_FileDiscovery(in.Discovery.File)

cmd/kubeadm/app/cmd/config.go

@@ -185,6 +185,9 @@ func getDefaultedInitConfig() (*kubeadmapi.InitConfiguration, error) {
 			KubernetesVersion: fmt.Sprintf("v1.%d.0", constants.MinimumControlPlaneVersion.Minor()+1),
 		},
 		BootstrapTokens: []kubeadmapiv1beta1.BootstrapToken{placeholderToken},
+		NodeRegistration: kubeadmapiv1beta1.NodeRegistrationOptions{
+			CRISocket: constants.DefaultDockerCRISocket, // avoid CRI detection
+		},
 	})
 }
 
@@ -206,6 +209,9 @@ func getDefaultNodeConfigBytes() ([]byte, error) {
 				UnsafeSkipCAVerification: true, // TODO: UnsafeSkipCAVerification: true needs to be set for validation to pass, but shouldn't be recommended as the default
 			},
 		},
+		NodeRegistration: kubeadmapiv1beta1.NodeRegistrationOptions{
+			CRISocket: constants.DefaultDockerCRISocket, // avoid CRI detection
+		},
 	})
 	if err != nil {
 		return []byte{}, err
@@ -430,7 +436,7 @@ func NewCmdConfigImagesPull() *cobra.Command {
 		},
 	}
 	AddImagesCommonConfigFlags(cmd.PersistentFlags(), externalcfg, &cfgPath, &featureGatesString)
-	AddImagesPullFlags(cmd.PersistentFlags(), externalcfg)
+	cmdutil.AddCRISocketFlag(cmd.PersistentFlags(), &externalcfg.NodeRegistration.CRISocket)
 
 	return cmd
 }
@@ -525,10 +531,3 @@ func AddImagesCommonConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiv1beta1.In
 		"Options are:\n"+strings.Join(features.KnownFeatures(&features.InitFeatureGates), "\n"))
 	flagSet.StringVar(cfgPath, "config", *cfgPath, "Path to kubeadm config file.")
 }
-
-// AddImagesPullFlags adds flags related to the `kubeadm config images pull` command
-func AddImagesPullFlags(flagSet *flag.FlagSet, cfg *kubeadmapiv1beta1.InitConfiguration) {
-	flagSet.StringVar(&cfg.NodeRegistration.CRISocket, "cri-socket", cfg.NodeRegistration.CRISocket, "Specify the CRI socket to connect to.")
-	flagSet.StringVar(&cfg.NodeRegistration.CRISocket, "cri-socket-path", cfg.NodeRegistration.CRISocket, "Path to the CRI socket.")
-	flagSet.MarkDeprecated("cri-socket-path", "Please, use --cri-socket instead")
-}

cmd/kubeadm/app/cmd/config_test.go

@@ -145,6 +145,9 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 				ClusterConfiguration: kubeadmapiv1beta1.ClusterConfiguration{
 					KubernetesVersion: dummyKubernetesVersion,
 				},
+				NodeRegistration: kubeadmapiv1beta1.NodeRegistrationOptions{
+					CRISocket: constants.DefaultDockerCRISocket,
+				},
 			},
 		},
 		{
@@ -158,6 +161,9 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 					},
 					KubernetesVersion: dummyKubernetesVersion,
 				},
+				NodeRegistration: kubeadmapiv1beta1.NodeRegistrationOptions{
+					CRISocket: constants.DefaultDockerCRISocket,
+				},
 			},
 			expectedImages: defaultNumberOfImages - 1,
 		},
@@ -167,6 +173,9 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 				ClusterConfiguration: kubeadmapiv1beta1.ClusterConfiguration{
 					KubernetesVersion: dummyKubernetesVersion,
 				},
+				NodeRegistration: kubeadmapiv1beta1.NodeRegistrationOptions{
+					CRISocket: constants.DefaultDockerCRISocket,
+				},
 			},
 			expectedImages: defaultNumberOfImages,
 		},
@@ -179,6 +188,9 @@ func TestConfigImagesListRunWithoutPath(t *testing.T) {
 						Type: kubeadmapiv1beta1.KubeDNS,
 					},
 				},
+				NodeRegistration: kubeadmapiv1beta1.NodeRegistrationOptions{
+					CRISocket: constants.DefaultDockerCRISocket,
+				},
 			},
 			expectedImages: defaultNumberOfImages + 2,
 		},
@@ -226,7 +238,7 @@ func TestImagesPull(t *testing.T) {
 		LookPathFunc: func(cmd string) (string, error) { return "/usr/bin/docker", nil },
 	}
 
-	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, kubeadmapiv1beta1.DefaultCRISocket)
+	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, constants.DefaultDockerCRISocket)
 	if err != nil {
 		t.Errorf("unexpected NewContainerRuntime error: %v", err)
 	}

cmd/kubeadm/app/cmd/init.go

@@ -230,10 +230,7 @@ func AddInitConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiv1beta1.InitConfig
 		&cfg.NodeRegistration.Name, options.NodeName, cfg.NodeRegistration.Name,
 		`Specify the node name.`,
 	)
-	flagSet.StringVar(
-		&cfg.NodeRegistration.CRISocket, options.NodeCRISocket, cfg.NodeRegistration.CRISocket,
-		`Specify the CRI socket to connect to.`,
-	)
+	cmdutil.AddCRISocketFlag(flagSet, &cfg.NodeRegistration.CRISocket)
 	flagSet.StringVar(featureGatesString, options.FeatureGatesString, *featureGatesString, "A set of key=value pairs that describe feature gates for various features. "+
 		"Options are:\n"+strings.Join(features.KnownFeatures(&features.InitFeatureGates), "\n"))
 }
@@ -316,7 +313,7 @@ func newInitData(cmd *cobra.Command, options *initOptions, out io.Writer) (initD
 	if options.externalcfg.NodeRegistration.Name != "" {
 		cfg.NodeRegistration.Name = options.externalcfg.NodeRegistration.Name
 	}
-	if options.externalcfg.NodeRegistration.CRISocket != kubeadmapiv1beta1.DefaultCRISocket {
+	if options.externalcfg.NodeRegistration.CRISocket != "" {
 		cfg.NodeRegistration.CRISocket = options.externalcfg.NodeRegistration.CRISocket
 	}
 

cmd/kubeadm/app/cmd/join.go

@@ -39,6 +39,7 @@ import (
 	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow"
+	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/discovery"
 	certsphase "k8s.io/kubernetes/cmd/kubeadm/app/phases/certs"
@@ -233,16 +234,13 @@ func AddJoinConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiv1beta1.JoinConfig
 		`Specify the node name.`,
 	)
 	flagSet.StringVar(
-		&cfg.NodeRegistration.CRISocket, options.NodeCRISocket, cfg.NodeRegistration.CRISocket,
-		`Specify the CRI socket to connect to.`,
-	)
-	flagSet.StringVar(
 		&cfg.Discovery.TLSBootstrapToken, options.TLSBootstrapToken, cfg.Discovery.TLSBootstrapToken,
 		`Specify the token used to temporarily authenticate with the Kubernetes Master while joining the node.`,
 	)
 	AddControlPlaneFlags(flagSet, cfg.ControlPlane)
 	AddJoinBootstrapTokenDiscoveryFlags(flagSet, cfg.Discovery.BootstrapToken)
 	AddJoinFileDiscoveryFlags(flagSet, cfg.Discovery.File)
+	cmdutil.AddCRISocketFlag(flagSet, &cfg.NodeRegistration.CRISocket)
 }
 
 // AddJoinBootstrapTokenDiscoveryFlags adds bootstrap token specific discovery flags to the specified flagset
@@ -388,7 +386,7 @@ func newJoinData(cmd *cobra.Command, options *joinOptions, out io.Writer) (joinD
 	if options.externalcfg.NodeRegistration.Name != "" {
 		cfg.NodeRegistration.Name = options.externalcfg.NodeRegistration.Name
 	}
-	if options.externalcfg.NodeRegistration.CRISocket != kubeadmapiv1beta1.DefaultCRISocket {
+	if options.externalcfg.NodeRegistration.CRISocket != "" {
 		cfg.NodeRegistration.CRISocket = options.externalcfg.NodeRegistration.CRISocket
 	}
 

cmd/kubeadm/app/cmd/reset.go

@@ -67,6 +67,12 @@ func NewCmdReset(in io.Reader, out io.Writer) *cobra.Command {
 				kubeadmutil.CheckErr(err)
 			}
 
+			if criSocketPath != "" {
+				criSocketPath, err = resetDetectCRISocket(client)
+				kubeadmutil.CheckErr(err)
+				klog.V(1).Infof("[reset] detected and using CRI socket: %s", criSocketPath)
+			}
+
 			r, err := NewReset(in, ignorePreflightErrorsSet, forceReset, certsDir, criSocketPath)
 			kubeadmutil.CheckErr(err)
 			kubeadmutil.CheckErr(r.Run(out, client))
@@ -81,10 +87,7 @@ func NewCmdReset(in io.Reader, out io.Writer) *cobra.Command {
 		"The path to the directory where the certificates are stored. If specified, clean this directory.",
 	)
 
-	cmd.PersistentFlags().StringVar(
-		&criSocketPath, "cri-socket", kubeadmapiv1beta1.DefaultCRISocket,
-		"The path to the CRI socket to use with crictl when cleaning up containers.",
-	)
+	cmdutil.AddCRISocketFlag(cmd.PersistentFlags(), &criSocketPath)
 
 	cmd.PersistentFlags().BoolVarP(
 		&forceReset, "force", "f", false,
@@ -295,3 +298,14 @@ func resetConfigDir(configPathDir, pkiPathDir string) {
 		}
 	}
 }
+
+func resetDetectCRISocket(client clientset.Interface) (string, error) {
+	// first try to connect to the cluster for the CRI socket
+	cfg, err := configutil.FetchConfigFromFileOrCluster(client, os.Stdout, "reset", "", false)
+	if err == nil {
+		return cfg.NodeRegistration.CRISocket, nil
+	}
+
+	// if this fails, try to detect it
+	return utilruntime.DetectCRISocket()
+}

cmd/kubeadm/app/cmd/reset_test.go

@@ -88,7 +88,7 @@ func assertDirEmpty(t *testing.T, path string) {
 func TestNewReset(t *testing.T) {
 	var in io.Reader
 	certsDir := kubeadmapiv1beta1.DefaultCertificatesDir
-	criSocketPath := kubeadmapiv1beta1.DefaultCRISocket
+	criSocketPath := kubeadmconstants.DefaultDockerCRISocket
 	forceReset := true
 
 	ignorePreflightErrors := []string{"all"}

cmd/kubeadm/app/cmd/upgrade/apply.go

@@ -29,6 +29,7 @@ import (
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmapiv1beta1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta1"
 	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
+	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
 	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/features"
@@ -70,7 +71,7 @@ func NewCmdApply(apf *applyPlanFlags) *cobra.Command {
 		applyPlanFlags:   apf,
 		imagePullTimeout: defaultImagePullTimeout,
 		etcdUpgrade:      true,
-		criSocket:        kubeadmapiv1beta1.DefaultCRISocket,
+		// Don't set criSocket to a default value here, as this will override the setting in the stored config in RunApply below.
 	}
 
 	cmd := &cobra.Command{
@@ -127,8 +128,11 @@ func NewCmdApply(apf *applyPlanFlags) *cobra.Command {
 	cmd.Flags().BoolVar(&flags.dryRun, "dry-run", flags.dryRun, "Do not change any state, just output what actions would be performed.")
 	cmd.Flags().BoolVar(&flags.etcdUpgrade, "etcd-upgrade", flags.etcdUpgrade, "Perform the upgrade of etcd.")
 	cmd.Flags().DurationVar(&flags.imagePullTimeout, "image-pull-timeout", flags.imagePullTimeout, "The maximum amount of time to wait for the control plane pods to be downloaded.")
-	// TODO: Register this flag in a generic place
-	cmd.Flags().StringVar(&flags.criSocket, "cri-socket", flags.criSocket, "Specify the CRI socket to connect to.")
+
+	// The CRI socket flag is deprecated here, since it should be taken from the NodeRegistrationOptions for the current
+	// node instead of the command line. This prevents errors by the users (such as attempts to use wrong CRI during upgrade).
+	cmdutil.AddCRISocketFlag(cmd.Flags(), &flags.criSocket)
+	cmd.Flags().MarkDeprecated(options.NodeCRISocket, "This flag is deprecated. Please, avoid using it.")
 	return cmd
 }
 

cmd/kubeadm/app/cmd/util/BUILD

@@ -10,6 +10,7 @@ go_library(
     importpath = "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util",
     visibility = ["//visibility:public"],
     deps = [
+        "//cmd/kubeadm/app/cmd/options:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/util/kubeconfig:go_default_library",
         "//cmd/kubeadm/app/util/pubkeypin:go_default_library",
@@ -18,6 +19,7 @@ go_library(
         "//staging/src/k8s.io/client-go/util/cert:go_default_library",
         "//vendor/github.com/pkg/errors:go_default_library",
         "//vendor/github.com/spf13/cobra:go_default_library",
+        "//vendor/github.com/spf13/pflag:go_default_library",
     ],
 )
 

cmd/kubeadm/app/cmd/util/cmdutil.go

@@ -19,8 +19,10 @@ package util
 import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
 
 	"k8s.io/client-go/tools/clientcmd"
+	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 )
 
@@ -73,3 +75,11 @@ func FindExistingKubeConfig(file string) string {
 	rules.Precedence = append(rules.Precedence, kubeadmconstants.GetAdminKubeConfigPath())
 	return rules.GetDefaultFilename()
 }
+
+// AddCRISocketFlag adds the cri-socket flag to the supplied flagSet
+func AddCRISocketFlag(flagSet *pflag.FlagSet, criSocket *string) {
+	flagSet.StringVar(
+		criSocket, options.NodeCRISocket, *criSocket,
+		"Path to the CRI socket to connect. If empty kubeadm will try to auto-detect this value; use this option only if you have more than one CRI installed or if you have non-standard CRI socket.",
+	)
+}

cmd/kubeadm/app/constants/BUILD

@@ -8,7 +8,11 @@ load(
 
 go_library(
     name = "go_default_library",
-    srcs = ["constants.go"],
+    srcs = [
+        "constants.go",
+        "constants_unix.go",
+        "constants_windows.go",
+    ],
     importpath = "k8s.io/kubernetes/cmd/kubeadm/app/constants",
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",

cmd/kubeadm/app/constants/constants_unix.go

+// +build !windows
+
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package constants
+
+const (
+	// DefaultDockerCRISocket defines the default Docker CRI socket
+	DefaultDockerCRISocket = "/var/run/dockershim.sock"
+)

cmd/kubeadm/app/constants/constants_windows.go

+// +build windows
+
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package constants
+
+const (
+	// DefaultDockerCRISocket defines the default Docker CRI socket
+	DefaultDockerCRISocket = "tcp://localhost:2375"
+)

cmd/kubeadm/app/phases/kubelet/BUILD

@@ -12,7 +12,6 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
-        "//cmd/kubeadm/app/apis/kubeadm/v1beta1:go_default_library",
         "//cmd/kubeadm/app/componentconfigs:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/images:go_default_library",

cmd/kubeadm/app/phases/kubelet/flags.go

@@ -26,7 +26,6 @@ import (
 	"github.com/pkg/errors"
 	"k8s.io/klog"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
-	kubeadmapiv1beta1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta1"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/images"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
@@ -74,7 +73,7 @@ func WriteKubeletDynamicEnvFile(cfg *kubeadmapi.InitConfiguration, registerTaint
 func buildKubeletArgMap(opts kubeletFlagsOpts) map[string]string {
 	kubeletFlags := map[string]string{}
 
-	if opts.nodeRegOpts.CRISocket == kubeadmapiv1beta1.DefaultCRISocket {
+	if opts.nodeRegOpts.CRISocket == constants.DefaultDockerCRISocket {
 		// These flags should only be set when running docker
 		kubeletFlags["network-plugin"] = "cni"
 		driver, err := kubeadmutil.GetCgroupDriverDocker(opts.execer)

cmd/kubeadm/app/preflight/BUILD

@@ -45,7 +45,6 @@ go_test(
     embed = [":go_default_library"],
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
-        "//cmd/kubeadm/app/apis/kubeadm/v1beta1:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/util/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/sets:go_default_library",

cmd/kubeadm/app/preflight/checks_test.go

@@ -31,7 +31,6 @@ import (
 
 	"k8s.io/apimachinery/pkg/util/sets"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
-	kubeadmapiv1beta1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta1"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	utilruntime "k8s.io/kubernetes/cmd/kubeadm/app/util/runtime"
 	"k8s.io/utils/exec"
@@ -756,7 +755,7 @@ func TestImagePullCheck(t *testing.T) {
 		LookPathFunc: func(cmd string) (string, error) { return "/usr/bin/docker", nil },
 	}
 
-	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, kubeadmapiv1beta1.DefaultCRISocket)
+	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, constants.DefaultDockerCRISocket)
 	if err != nil {
 		t.Errorf("unexpected NewContainerRuntime error: %v", err)
 	}

cmd/kubeadm/app/util/config/BUILD

@@ -24,6 +24,7 @@ go_library(
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/util:go_default_library",
         "//cmd/kubeadm/app/util/config/strict:go_default_library",
+        "//cmd/kubeadm/app/util/runtime:go_default_library",
         "//pkg/util/node:go_default_library",
         "//staging/src/k8s.io/api/core/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/api/errors:go_default_library",

cmd/kubeadm/app/util/config/initconfiguration.go

@@ -40,6 +40,7 @@ import (
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/config/strict"
+	kubeadmruntime "k8s.io/kubernetes/cmd/kubeadm/app/util/runtime"
 	nodeutil "k8s.io/kubernetes/pkg/util/node"
 )
 
@@ -96,6 +97,14 @@ func SetNodeRegistrationDynamicDefaults(cfg *kubeadmapi.NodeRegistrationOptions,
 		cfg.Taints = []v1.Taint{kubeadmconstants.MasterTaint}
 	}
 
+	if cfg.CRISocket == "" {
+		cfg.CRISocket, err = kubeadmruntime.DetectCRISocket()
+		if err != nil {
+			return err
+		}
+		klog.V(1).Infof("detected and using CRI socket: %s", cfg.CRISocket)
+	}
+
 	return nil
 }
 

cmd/kubeadm/app/util/runtime/BUILD

@@ -6,7 +6,7 @@ go_library(
     importpath = "k8s.io/kubernetes/cmd/kubeadm/app/util/runtime",
     visibility = ["//visibility:public"],
     deps = [
-        "//cmd/kubeadm/app/apis/kubeadm/v1beta1:go_default_library",
+        "//cmd/kubeadm/app/constants:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/util/errors:go_default_library",
         "//vendor/github.com/pkg/errors:go_default_library",
         "//vendor/k8s.io/utils/exec:go_default_library",
@@ -18,7 +18,7 @@ go_test(
     srcs = ["runtime_test.go"],
     embed = [":go_default_library"],
     deps = [
-        "//cmd/kubeadm/app/apis/kubeadm/v1beta1:go_default_library",
+        "//cmd/kubeadm/app/constants:go_default_library",
         "//vendor/github.com/pkg/errors:go_default_library",
         "//vendor/k8s.io/utils/exec:go_default_library",
         "//vendor/k8s.io/utils/exec/testing:go_default_library",

cmd/kubeadm/app/util/runtime/runtime.go

@@ -17,6 +17,7 @@ limitations under the License.
 package util
 
 import (
+	"os"
 	"path/filepath"
 	goruntime "runtime"
 	"strings"
@@ -24,7 +25,7 @@ import (
 	"github.com/pkg/errors"
 
 	errorsutil "k8s.io/apimachinery/pkg/util/errors"
-	kubeadmapiv1beta1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta1"
+	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	utilsexec "k8s.io/utils/exec"
 )
 
@@ -54,7 +55,7 @@ func NewContainerRuntime(execer utilsexec.Interface, criSocket string) (Containe
 	var toolName string
 	var runtime ContainerRuntime
 
-	if criSocket != kubeadmapiv1beta1.DefaultCRISocket {
+	if criSocket != constants.DefaultDockerCRISocket {
 		toolName = "crictl"
 		// !!! temporary work around crictl warning:
 		// Using "/var/run/crio/crio.sock" as endpoint is deprecated,
@@ -180,3 +181,63 @@ func (runtime *DockerRuntime) ImageExists(image string) (bool, error) {
 	err := runtime.exec.Command("docker", "inspect", image).Run()
 	return err == nil, nil
 }
+
+// isExistingSocket checks if path exists and is domain socket
+func isExistingSocket(path string) bool {
+	fileInfo, err := os.Stat(path)
+	if err != nil {
+		return false
+	}
+
+	return fileInfo.Mode()&os.ModeSocket != 0
+}
+
+// detectCRISocketImpl is separated out only for test purposes, DON'T call it directly, use DetectCRISocket instead
+func detectCRISocketImpl(isSocket func(string) bool) (string, error) {
+	const (
+		dockerSocket     = "/var/run/docker.sock" // The Docker socket is not CRI compatible
+		containerdSocket = "/run/containerd/containerd.sock"
+	)
+
+	foundCRISockets := []string{}
+	knownCRISockets := []string{
+		// Docker and containerd sockets are special cased below, hence not to be included here
+		"/var/run/crio/crio.sock",
+	}
+
+	if isSocket(dockerSocket) {
+		// the path in dockerSocket is not CRI compatible, hence we should replace it with a CRI compatible socket
+		foundCRISockets = append(foundCRISockets, constants.DefaultDockerCRISocket)
+	} else if isSocket(containerdSocket) {
+		// Docker 18.09 gets bundled together with containerd, thus having both dockerSocket and containerdSocket present.
+		// For compatibility reasons, we use the containerd socket only if Docker is not detected.
+		foundCRISockets = append(foundCRISockets, containerdSocket)
+	}
+
+	for _, socket := range knownCRISockets {
+		if isSocket(socket) {
+			foundCRISockets = append(foundCRISockets, socket)
+		}
+	}
+
+	switch len(foundCRISockets) {
+	case 0:
+		// Fall back to Docker if no CRI is detected, we can error out later on if we need it
+		return constants.DefaultDockerCRISocket, nil
+	case 1:
+		// Precisely one CRI found, use that
+		return foundCRISockets[0], nil
+	default:
+		// Multiple CRIs installed?
+		return "", errors.Errorf("Found multiple CRI sockets, please use --cri-socket to select one: %s", strings.Join(foundCRISockets, ", "))
+	}
+}
+
+// DetectCRISocket uses a list of known CRI sockets to detect one. If more than one or none is discovered, an error is returned.
+func DetectCRISocket() (string, error) {
+	if goruntime.GOOS != "linux" {
+		return constants.DefaultDockerCRISocket, nil
+	}
+
+	return detectCRISocketImpl(isExistingSocket)
+}

cmd/kubeadm/app/util/runtime/runtime_test.go

@@ -17,12 +17,16 @@ limitations under the License.
 package util
 
 import (
+	"io/ioutil"
+	"net"
+	"os"
 	"reflect"
+	"runtime"
 	"testing"
 
 	"github.com/pkg/errors"
 
-	kubeadmapiv1beta1 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1beta1"
+	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/utils/exec"
 	fakeexec "k8s.io/utils/exec/testing"
 )
@@ -41,7 +45,7 @@ func TestNewContainerRuntime(t *testing.T) {
 		isDocker  bool
 		isError   bool
 	}{
-		{"valid: default cri socket", execLookPathOK, kubeadmapiv1beta1.DefaultCRISocket, true, false},
+		{"valid: default cri socket", execLookPathOK, constants.DefaultDockerCRISocket, true, false},
 		{"valid: cri-o socket url", execLookPathOK, "unix:///var/run/crio/crio.sock", false, false},
 		{"valid: cri-o socket path", execLookPathOK, "/var/run/crio/crio.sock", false, false},
 		{"invalid: no crictl", execLookPathErr, "unix:///var/run/crio/crio.sock", false, true},
@@ -105,8 +109,8 @@ func TestIsRunning(t *testing.T) {
 	}{
 		{"valid: CRI-O is running", "unix:///var/run/crio/crio.sock", criExecer, false},
 		{"invalid: CRI-O is not running", "unix:///var/run/crio/crio.sock", criExecer, true},
-		{"valid: docker is running", kubeadmapiv1beta1.DefaultCRISocket, dockerExecer, false},
-		{"invalid: docker is not running", kubeadmapiv1beta1.DefaultCRISocket, dockerExecer, true},
+		{"valid: docker is running", constants.DefaultDockerCRISocket, dockerExecer, false},
+		{"invalid: docker is not running", constants.DefaultDockerCRISocket, dockerExecer, true},
 	}
 
 	for _, tc := range cases {
@@ -146,7 +150,7 @@ func TestListKubeContainers(t *testing.T) {
 	}{
 		{"valid: list containers using CRI socket url", "unix:///var/run/crio/crio.sock", false},
 		{"invalid: list containers using CRI socket url", "unix:///var/run/crio/crio.sock", true},
-		{"valid: list containers using docker", kubeadmapiv1beta1.DefaultCRISocket, false},
+		{"valid: list containers using docker", constants.DefaultDockerCRISocket, false},
 	}
 
 	for _, tc := range cases {
@@ -199,8 +203,8 @@ func TestRemoveContainers(t *testing.T) {
 		{"valid: remove containers using CRI", "unix:///var/run/crio/crio.sock", []string{"k8s_p1", "k8s_p2", "k8s_p3"}, false}, // Test case 1
 		{"invalid: CRI rmp failure", "unix:///var/run/crio/crio.sock", []string{"k8s_p1", "k8s_p2", "k8s_p3"}, true},
 		{"invalid: CRI stopp failure", "unix:///var/run/crio/crio.sock", []string{"k8s_p1", "k8s_p2", "k8s_p3"}, true},
-		{"valid: remove containers using docker", kubeadmapiv1beta1.DefaultCRISocket, []string{"k8s_c1", "k8s_c2", "k8s_c3"}, false},
-		{"invalid: remove containers using docker", kubeadmapiv1beta1.DefaultCRISocket, []string{"k8s_c1", "k8s_c2", "k8s_c3"}, true},
+		{"valid: remove containers using docker", constants.DefaultDockerCRISocket, []string{"k8s_c1", "k8s_c2", "k8s_c3"}, false},
+		{"invalid: remove containers using docker", constants.DefaultDockerCRISocket, []string{"k8s_c1", "k8s_c2", "k8s_c3"}, true},
 	}
 
 	for _, tc := range cases {
@@ -243,8 +247,8 @@ func TestPullImage(t *testing.T) {
 	}{
 		{"valid: pull image using CRI", "unix:///var/run/crio/crio.sock", "image1", false},
 		{"invalid: CRI pull error", "unix:///var/run/crio/crio.sock", "image2", true},
-		{"valid: pull image using docker", kubeadmapiv1beta1.DefaultCRISocket, "image1", false},
-		{"invalide: docer pull error", kubeadmapiv1beta1.DefaultCRISocket, "image2", true},
+		{"valid: pull image using docker", constants.DefaultDockerCRISocket, "image1", false},
+		{"invalide: docer pull error", constants.DefaultDockerCRISocket, "image2", true},
 	}
 
 	for _, tc := range cases {
@@ -287,8 +291,8 @@ func TestImageExists(t *testing.T) {
 	}{
 		{"valid: test if image exists using CRI", "unix:///var/run/crio/crio.sock", "image1", false},
 		{"invalid: CRI inspecti failure", "unix:///var/run/crio/crio.sock", "image2", true},
-		{"valid: test if image exists using docker", kubeadmapiv1beta1.DefaultCRISocket, "image1", false},
-		{"invalid: docker inspect failure", kubeadmapiv1beta1.DefaultCRISocket, "image2", true},
+		{"valid: test if image exists using docker", constants.DefaultDockerCRISocket, "image1", false},
+		{"invalid: docker inspect failure", constants.DefaultDockerCRISocket, "image2", true},
 	}
 
 	for _, tc := range cases {
@@ -305,3 +309,142 @@ func TestImageExists(t *testing.T) {
 		})
 	}
 }
+
+func TestIsExistingSocket(t *testing.T) {
+	// this test is not expected to work on Windows
+	if runtime.GOOS == "windows" {
+		return
+	}
+
+	const tempPrefix = "test.kubeadm.runtime.isExistingSocket."
+	tests := []struct {
+		name string
+		proc func(*testing.T)
+	}{
+		{
+			name: "Valid domain socket is detected as such",
+			proc: func(t *testing.T) {
+				tmpFile, err := ioutil.TempFile("", tempPrefix)
+				if err != nil {
+					t.Fatalf("unexpected error by TempFile: %v", err)
+				}
+				theSocket := tmpFile.Name()
+				os.Remove(theSocket)
+				tmpFile.Close()
+
+				con, err := net.Listen("unix", theSocket)
+				if err != nil {
+					t.Fatalf("unexpected error while dialing a socket: %v", err)
+				}
+				defer con.Close()
+
+				if !isExistingSocket(theSocket) {
+					t.Fatalf("isExistingSocket(%q) gave unexpected result. Should have been true, instead of false", theSocket)
+				}
+			},
+		},
+		{
+			name: "Regular file is not a domain socket",
+			proc: func(t *testing.T) {
+				tmpFile, err := ioutil.TempFile("", tempPrefix)
+				if err != nil {
+					t.Fatalf("unexpected error by TempFile: %v", err)
+				}
+				theSocket := tmpFile.Name()
+				defer os.Remove(theSocket)
+				tmpFile.Close()
+
+				if isExistingSocket(theSocket) {
+					t.Fatalf("isExistingSocket(%q) gave unexpected result. Should have been false, instead of true", theSocket)
+				}
+			},
+		},
+		{
+			name: "Non existent socket is not a domain socket",
+			proc: func(t *testing.T) {
+				const theSocket = "/non/existent/socket"
+				if isExistingSocket(theSocket) {
+					t.Fatalf("isExistingSocket(%q) gave unexpected result. Should have been false, instead of true", theSocket)
+				}
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, test.proc)
+	}
+}
+
+func TestDetectCRISocketImpl(t *testing.T) {
+	tests := []struct {
+		name            string
+		existingSockets []string
+		expectedError   bool
+		expectedSocket  string
+	}{
+		{
+			name:            "No existing sockets, use Docker",
+			existingSockets: []string{},
+			expectedError:   false,
+			expectedSocket:  constants.DefaultDockerCRISocket,
+		},
+		{
+			name:            "One valid CRI socket leads to success",
+			existingSockets: []string{"/var/run/crio/crio.sock"},
+			expectedError:   false,
+			expectedSocket:  "/var/run/crio/crio.sock",
+		},
+		{
+			name:            "Correct Docker CRI socket is returned",
+			existingSockets: []string{"/var/run/docker.sock"},
+			expectedError:   false,
+			expectedSocket:  constants.DefaultDockerCRISocket,
+		},
+		{
+			name: "CRI and Docker sockets lead to an error",
+			existingSockets: []string{
+				"/var/run/docker.sock",
+				"/var/run/crio/crio.sock",
+			},
+			expectedError: true,
+		},
+		{
+			name: "Docker and containerd lead to Docker being used",
+			existingSockets: []string{
+				"/var/run/docker.sock",
+				"/run/containerd/containerd.sock",
+			},
+			expectedError:  false,
+			expectedSocket: constants.DefaultDockerCRISocket,
+		},
+		{
+			name: "A couple of CRI sockets lead to an error",
+			existingSockets: []string{
+				"/var/run/crio/crio.sock",
+				"/run/containerd/containerd.sock",
+			},
+			expectedError: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			socket, err := detectCRISocketImpl(func(path string) bool {
+				for _, existing := range test.existingSockets {
+					if path == existing {
+						return true
+					}
+				}
+
+				return false
+			})
+			if (err != nil) != test.expectedError {
+				t.Fatalf("detectCRISocketImpl returned unexpected result\n\tExpected error: %t\n\tGot error: %t", test.expectedError, err != nil)
+			}
+			if !test.expectedError && socket != test.expectedSocket {
+				t.Fatalf("detectCRISocketImpl returned unexpected CRI socket\n\tExpected socket: %s\n\tReturned socket: %s",
+					test.expectedSocket, socket)
+			}
+		})
+	}
+}