Merge pull request #107317 from neolit123/1.24-change-kubeadm-cr-auto-detection

kubeadm: adapt CRI detection and defaults after the dockershim removal

cmd/kubeadm/app/apis/kubeadm/v1beta2/doc.go

@@ -169,7 +169,7 @@ limitations under the License.
 // 	  - system:bootstrappers:kubeadm:default-node-token
 // 	nodeRegistration:
 // 	  name: "ec2-10-100-0-1"
-// 	  criSocket: "unix:///var/run/dockershim.sock"
+// 	  criSocket: "unix:///var/run/containerd/containerd.sock"
 // 	  taints:
 // 	  - key: "kubeadmNode"
 // 	    value: "master"

cmd/kubeadm/app/apis/kubeadm/v1beta3/doc.go

@@ -173,7 +173,7 @@ limitations under the License.
 // 	  - system:bootstrappers:kubeadm:default-node-token
 // 	nodeRegistration:
 // 	  name: "ec2-10-100-0-1"
-// 	  criSocket: "unix:///var/run/dockershim.sock"
+// 	  criSocket: "unix:///var/run/containerd/containerd.sock"
 // 	  taints:
 // 	  - key: "kubeadmNode"
 // 	    value: "master"

cmd/kubeadm/app/apis/kubeadm/validation/validation_test.go

@@ -579,7 +579,7 @@ func TestValidateJoinConfiguration(t *testing.T) {
 			},
 			NodeRegistration: kubeadmapi.NodeRegistrationOptions{
 				Name:      "aaa",
-				CRISocket: "unix:///var/run/dockershim.sock",
+				CRISocket: "unix:///var/run/containerd/containerd.sock",
 			},
 		}, true},
 		{&kubeadmapi.JoinConfiguration{ // Pass with JoinControlPlane
@@ -594,7 +594,7 @@ func TestValidateJoinConfiguration(t *testing.T) {
 			},
 			NodeRegistration: kubeadmapi.NodeRegistrationOptions{
 				Name:      "aaa",
-				CRISocket: "unix:///var/run/dockershim.sock",
+				CRISocket: "unix:///var/run/containerd/containerd.sock",
 			},
 			ControlPlane: &kubeadmapi.JoinControlPlane{
 				LocalAPIEndpoint: kubeadmapi.APIEndpoint{
@@ -615,7 +615,7 @@ func TestValidateJoinConfiguration(t *testing.T) {
 			},
 			NodeRegistration: kubeadmapi.NodeRegistrationOptions{
 				Name:      "aaa",
-				CRISocket: "unix:///var/run/dockershim.sock",
+				CRISocket: "unix:///var/run/containerd/containerd.sock",
 			},
 			ControlPlane: &kubeadmapi.JoinControlPlane{
 				LocalAPIEndpoint: kubeadmapi.APIEndpoint{
@@ -636,7 +636,7 @@ func TestValidateJoinConfiguration(t *testing.T) {
 			},
 			NodeRegistration: kubeadmapi.NodeRegistrationOptions{
 				Name:      "aaa",
-				CRISocket: "/var/run/dockershim.sock",
+				CRISocket: "unix:///var/run/containerd/containerd.sock",
 			},
 			ControlPlane: &kubeadmapi.JoinControlPlane{
 				LocalAPIEndpoint: kubeadmapi.APIEndpoint{

cmd/kubeadm/app/cmd/certs_test.go

@@ -359,7 +359,7 @@ kind: InitConfiguration
 localAPIEndpoint:
   advertiseAddress: 192.0.2.1
 nodeRegistration:
-  criSocket: /path/to/dockershim.sock
+  criSocket: "unix:///var/run/containerd/containerd.sock"
 ---
 apiVersion: %[1]s
 kind: ClusterConfiguration

cmd/kubeadm/app/cmd/config.go

@@ -211,7 +211,7 @@ func getDefaultNodeConfigBytes() ([]byte, error) {
 			},
 		},
 		NodeRegistration: kubeadmapiv1.NodeRegistrationOptions{
-			CRISocket: constants.DefaultDockerCRISocket, // avoid CRI detection
+			CRISocket: constants.DefaultCRISocket, // avoid CRI detection
 		},
 	})
 	if err != nil {

cmd/kubeadm/app/cmd/config_test.go

@@ -363,10 +363,10 @@ func TestImagesPull(t *testing.T) {
 			func(cmd string, args ...string) exec.Cmd { return fakeexec.InitFakeCmd(&fcmd, cmd, args...) },
 			func(cmd string, args ...string) exec.Cmd { return fakeexec.InitFakeCmd(&fcmd, cmd, args...) },
 		},
-		LookPathFunc: func(cmd string) (string, error) { return "/usr/bin/docker", nil },
+		LookPathFunc: func(cmd string) (string, error) { return "/usr/bin/crictl", nil },
 	}
 
-	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, constants.DefaultDockerCRISocket)
+	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, constants.DefaultCRISocket)
 	if err != nil {
 		t.Errorf("unexpected NewContainerRuntime error: %v", err)
 	}

cmd/kubeadm/app/cmd/phases/init/waitcontrolplane.go

@@ -29,7 +29,6 @@ import (
 	"k8s.io/klog/v2"
 
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow"
-	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/util/apiclient"
 	dryrunutil "k8s.io/kubernetes/cmd/kubeadm/app/util/dryrun"
 )
@@ -49,17 +48,10 @@ var (
 
 	Additionally, a control plane component may have crashed or exited when started by the container runtime.
 	To troubleshoot, list all containers using your preferred container runtimes CLI.
-{{ if .IsDocker }}
-	Here is one example how you may list all Kubernetes containers running in docker:
-		- 'docker ps -a | grep kube | grep -v pause'
-		Once you have found the failing container, you can inspect its logs with:
-		- 'docker logs CONTAINERID'
-{{ else }}
-	Here is one example how you may list all Kubernetes containers running in cri-o/containerd using crictl:
+	Here is one example how you may list all running Kubernetes containers by using crictl:
 		- 'crictl --runtime-endpoint {{ .Socket }} ps -a | grep kube | grep -v pause'
 		Once you have found the failing container, you can inspect its logs with:
 		- 'crictl --runtime-endpoint {{ .Socket }} logs CONTAINERID'
-{{ end }}
 	`)))
 )
 
@@ -105,13 +97,11 @@ func runWaitControlPlanePhase(c workflow.RunData) error {
 
 	if err := waiter.WaitForKubeletAndFunc(waiter.WaitForAPI); err != nil {
 		context := struct {
-			Error    string
-			Socket   string
-			IsDocker bool
+			Error  string
+			Socket string
 		}{
-			Error:    fmt.Sprintf("%v", err),
-			Socket:   data.Cfg().NodeRegistration.CRISocket,
-			IsDocker: data.Cfg().NodeRegistration.CRISocket == kubeadmconstants.DefaultDockerCRISocket,
+			Error:  fmt.Sprintf("%v", err),
+			Socket: data.Cfg().NodeRegistration.CRISocket,
 		}
 
 		kubeletFailTempl.Execute(data.OutputWriter(), context)

cmd/kubeadm/app/cmd/phases/reset/cleanupnode.go

@@ -96,6 +96,8 @@ func runCleanupNode(c workflow.RunData) error {
 		fmt.Println("[reset] Would remove Kubernetes-managed containers")
 	}
 
+	// TODO: remove the dockershim directory cleanup in 1.25
+	// https://github.com/kubernetes/kubeadm/issues/2626
 	r.AddDirsToClean("/var/lib/dockershim", "/var/run/kubernetes", "/var/lib/cni")
 
 	// Remove contents from the config and pki directories

cmd/kubeadm/app/constants/constants_unix.go

@@ -20,6 +20,13 @@ limitations under the License.
 package constants
 
 const (
-	// DefaultDockerCRISocket defines the default Docker CRI socket
-	DefaultDockerCRISocket = "unix:///var/run/dockershim.sock"
+	// CRISocketContainerd is the containerd CRI endpoint
+	CRISocketContainerd = "unix:///var/run/containerd/containerd.sock"
+	// CRISocketCRIO is the cri-o CRI endpoint
+	CRISocketCRIO = "unix:///var/run/crio/crio.sock"
+	// CRISocketDocker is the cri-dockerd CRI endpoint
+	CRISocketDocker = "unix:///var/run/cri-dockerd.sock"
+
+	// DefaultCRISocket defines the default CRI socket
+	DefaultCRISocket = CRISocketContainerd
 )

cmd/kubeadm/app/constants/constants_windows.go

@@ -20,6 +20,14 @@ limitations under the License.
 package constants
 
 const (
-	// DefaultDockerCRISocket defines the default Docker CRI socket
-	DefaultDockerCRISocket = "npipe:////./pipe/docker_engine"
+	// CRISocketContainerd is the containerd CRI endpoint
+	CRISocketContainerd = "npipe:////./pipe/containerd-containerd"
+	// CRISocketCRIO is the cri-o CRI endpoint
+	// NOTE: this is a placeholder as CRI-O does not support Windows
+	CRISocketCRIO = "npipe:////./pipe/cri-o"
+	// CRISocketDocker is the cri-dockerd CRI endpoint
+	CRISocketDocker = "npipe:////./pipe/cri-dockerd"
+
+	// DefaultCRISocket defines the default CRI socket
+	DefaultCRISocket = CRISocketContainerd
 )

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

@@ -21,6 +21,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 
 	"github.com/pkg/errors"
@@ -102,7 +103,13 @@ func buildKubeletArgMapCommon(opts kubeletFlagsOpts) map[string]string {
 	// Once that happens only the "remote" branch option should be left.
 	// TODO: https://github.com/kubernetes/kubeadm/issues/2626
 	hasDockershim := opts.kubeletVersion.Major() == 1 && opts.kubeletVersion.Minor() < 24
-	if opts.nodeRegOpts.CRISocket == constants.DefaultDockerCRISocket && hasDockershim {
+	var dockerSocket string
+	if runtime.GOOS == "windows" {
+		dockerSocket = "npipe:////./pipe/dockershim"
+	} else {
+		dockerSocket = "unix:///var/run/dockershim.sock"
+	}
+	if opts.nodeRegOpts.CRISocket == dockerSocket && hasDockershim {
 		kubeletFlags["network-plugin"] = "cni"
 	} else {
 		kubeletFlags["container-runtime"] = "remote"

cmd/kubeadm/app/phases/patchnode/patchnode_test.go

@@ -52,7 +52,7 @@ func TestAnnotateCRISocket(t *testing.T) {
 		},
 		{
 			name:                       "CRI-socket annotation needs to be updated",
-			currentCRISocketAnnotation: "unix:///var/run/dockershim.sock",
+			currentCRISocketAnnotation: "unix:///foo/bar",
 			newCRISocketAnnotation:     "unix:///run/containerd/containerd.sock",
 			expectedPatch:              `{"metadata":{"annotations":{"kubeadm.alpha.kubernetes.io/cri-socket":"unix:///run/containerd/containerd.sock"}}}`,
 		},

cmd/kubeadm/app/preflight/checks.go

@@ -507,9 +507,7 @@ func (subnet HTTPProxyCIDRCheck) Check() (warnings, errorList []error) {
 }
 
 // SystemVerificationCheck defines struct used for running the system verification node check in test/e2e_node/system
-type SystemVerificationCheck struct {
-	IsDocker bool
-}
+type SystemVerificationCheck struct{}
 
 // Name will return SystemVerification as name for SystemVerificationCheck
 func (SystemVerificationCheck) Name() string {
@@ -530,11 +528,6 @@ func (sysver SystemVerificationCheck) Check() (warnings, errorList []error) {
 	var validators = []system.Validator{
 		&system.KernelValidator{Reporter: reporter}}
 
-	// run the docker validator only with docker runtime
-	if sysver.IsDocker {
-		validators = append(validators, &system.DockerValidator{Reporter: reporter})
-	}
-
 	if runtime.GOOS == "linux" {
 		//add linux validators
 		validators = append(validators,
@@ -1025,26 +1018,19 @@ func RunJoinNodeChecks(execer utilsexec.Interface, cfg *kubeadmapi.JoinConfigura
 // kubeadm init and join commands
 func addCommonChecks(execer utilsexec.Interface, k8sVersion string, nodeReg *kubeadmapi.NodeRegistrationOptions, checks []Checker) []Checker {
 	containerRuntime, err := utilruntime.NewContainerRuntime(execer, nodeReg.CRISocket)
-	isDocker := false
 	if err != nil {
 		klog.Warningf("[preflight] WARNING: Couldn't create the interface used for talking to the container runtime: %v\n", err)
 	} else {
 		checks = append(checks, ContainerRuntimeCheck{runtime: containerRuntime})
-		if containerRuntime.IsDocker() {
-			isDocker = true
-			checks = append(checks, ServiceCheck{Service: "docker", CheckIfActive: true})
-		}
 	}
 
 	// non-windows checks
 	if runtime.GOOS == "linux" {
-		if !isDocker {
-			checks = append(checks, InPathCheck{executable: "crictl", mandatory: true, exec: execer})
-		}
 		checks = append(checks,
 			FileContentCheck{Path: bridgenf, Content: []byte{'1'}},
 			FileContentCheck{Path: ipv4Forward, Content: []byte{'1'}},
 			SwapCheck{},
+			InPathCheck{executable: "crictl", mandatory: true, exec: execer},
 			InPathCheck{executable: "conntrack", mandatory: true, exec: execer},
 			InPathCheck{executable: "ip", mandatory: true, exec: execer},
 			InPathCheck{executable: "iptables", mandatory: true, exec: execer},
@@ -1057,7 +1043,7 @@ func addCommonChecks(execer utilsexec.Interface, k8sVersion string, nodeReg *kub
 			InPathCheck{executable: "touch", mandatory: false, exec: execer})
 	}
 	checks = append(checks,
-		SystemVerificationCheck{IsDocker: isDocker},
+		SystemVerificationCheck{},
 		HostnameCheck{nodeName: nodeReg.Name},
 		KubeletVersionCheck{KubernetesVersion: k8sVersion, exec: execer},
 		ServiceCheck{Service: "kubelet", CheckIfActive: false},

cmd/kubeadm/app/preflight/checks_test.go

@@ -917,10 +917,10 @@ func TestImagePullCheck(t *testing.T) {
 			func(cmd string, args ...string) exec.Cmd { return fakeexec.InitFakeCmd(&fcmd, cmd, args...) },
 			func(cmd string, args ...string) exec.Cmd { return fakeexec.InitFakeCmd(&fcmd, cmd, args...) },
 		},
-		LookPathFunc: func(cmd string) (string, error) { return "/usr/bin/docker", nil },
+		LookPathFunc: func(cmd string) (string, error) { return "/usr/bin/crictl", nil },
 	}
 
-	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, constants.DefaultDockerCRISocket)
+	containerRuntime, err := utilruntime.NewContainerRuntime(&fexec, constants.DefaultCRISocket)
 	if err != nil {
 		t.Errorf("unexpected NewContainerRuntime error: %v", err)
 	}

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

@@ -195,7 +195,7 @@ func DefaultedStaticInitConfiguration() (*kubeadmapi.InitConfiguration, error) {
 		LocalAPIEndpoint: kubeadmapiv1.APIEndpoint{AdvertiseAddress: "1.2.3.4"},
 		BootstrapTokens:  []bootstraptokenv1.BootstrapToken{PlaceholderToken},
 		NodeRegistration: kubeadmapiv1.NodeRegistrationOptions{
-			CRISocket: kubeadmconstants.DefaultDockerCRISocket, // avoid CRI detection
+			CRISocket: kubeadmconstants.DefaultCRISocket, // avoid CRI detection
 			Name:      "node",
 		},
 	}

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

@@ -27,9 +27,16 @@ import (
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 )
 
+// defaultKnownCRISockets holds the set of known CRI endpoints
+var defaultKnownCRISockets = []string{
+	constants.CRISocketContainerd,
+	constants.CRISocketCRIO,
+	constants.CRISocketDocker,
+}
+
 // ContainerRuntime is an interface for working with container runtimes
 type ContainerRuntime interface {
-	IsDocker() bool
+	Socket() string
 	IsRunning() error
 	ListKubeContainers() ([]string, error)
 	RemoveContainers(containers []string) error
@@ -43,39 +50,19 @@ type CRIRuntime struct {
 	criSocket string
 }
 
-// DockerRuntime is a struct that interfaces with the Docker daemon
-type DockerRuntime struct {
-	exec utilsexec.Interface
-}
-
 // NewContainerRuntime sets up and returns a ContainerRuntime struct
 func NewContainerRuntime(execer utilsexec.Interface, criSocket string) (ContainerRuntime, error) {
-	var toolName string
-	var runtime ContainerRuntime
-
-	if criSocket != constants.DefaultDockerCRISocket {
-		toolName = "crictl"
-		runtime = &CRIRuntime{execer, criSocket}
-	} else {
-		toolName = "docker"
-		runtime = &DockerRuntime{execer}
-	}
-
+	toolName := "crictl"
+	runtime := &CRIRuntime{execer, criSocket}
 	if _, err := execer.LookPath(toolName); err != nil {
-		return nil, errors.Wrapf(err, "%s is required for container runtime", toolName)
+		return nil, errors.Wrapf(err, "%s is required by the container runtime", toolName)
 	}
-
 	return runtime, nil
 }
 
-// IsDocker returns true if the runtime is docker
-func (runtime *CRIRuntime) IsDocker() bool {
-	return false
-}
-
-// IsDocker returns true if the runtime is docker
-func (runtime *DockerRuntime) IsDocker() bool {
-	return true
+// Socket returns the CRI socket endpoint
+func (runtime *CRIRuntime) Socket() string {
+	return runtime.criSocket
 }
 
 // IsRunning checks if runtime is running
@@ -86,14 +73,6 @@ func (runtime *CRIRuntime) IsRunning() error {
 	return nil
 }
 
-// IsRunning checks if runtime is running
-func (runtime *DockerRuntime) IsRunning() error {
-	if out, err := runtime.exec.Command("docker", "info").CombinedOutput(); err != nil {
-		return errors.Wrapf(err, "container runtime is not running: output: %s, error", string(out))
-	}
-	return nil
-}
-
 // ListKubeContainers lists running k8s CRI pods
 func (runtime *CRIRuntime) ListKubeContainers() ([]string, error) {
 	out, err := runtime.exec.Command("crictl", "-r", runtime.criSocket, "pods", "-q").CombinedOutput()
@@ -105,12 +84,6 @@ func (runtime *CRIRuntime) ListKubeContainers() ([]string, error) {
 	return pods, nil
 }
 
-// ListKubeContainers lists running k8s containers
-func (runtime *DockerRuntime) ListKubeContainers() ([]string, error) {
-	output, err := runtime.exec.Command("docker", "ps", "-a", "--filter", "name=k8s_", "-q").CombinedOutput()
-	return strings.Fields(string(output)), err
-}
-
 // RemoveContainers removes running k8s pods
 func (runtime *CRIRuntime) RemoveContainers(containers []string) error {
 	errs := []error{}
@@ -129,24 +102,6 @@ func (runtime *CRIRuntime) RemoveContainers(containers []string) error {
 	return errorsutil.NewAggregate(errs)
 }
 
-// RemoveContainers removes running containers
-func (runtime *DockerRuntime) RemoveContainers(containers []string) error {
-	errs := []error{}
-	for _, container := range containers {
-		out, err := runtime.exec.Command("docker", "stop", container).CombinedOutput()
-		if err != nil {
-			// don't stop on errors, try to remove as many containers as possible
-			errs = append(errs, errors.Wrapf(err, "failed to stop running container %s: output: %s, error", container, string(out)))
-		} else {
-			out, err = runtime.exec.Command("docker", "rm", "--volumes", container).CombinedOutput()
-			if err != nil {
-				errs = append(errs, errors.Wrapf(err, "failed to remove running container %s: output: %s, error", container, string(out)))
-			}
-		}
-	}
-	return errorsutil.NewAggregate(errs)
-}
-
 // PullImage pulls the image
 func (runtime *CRIRuntime) PullImage(image string) error {
 	var err error
@@ -160,47 +115,15 @@ func (runtime *CRIRuntime) PullImage(image string) error {
 	return errors.Wrapf(err, "output: %s, error", out)
 }
 
-// PullImage pulls the image
-func (runtime *DockerRuntime) PullImage(image string) error {
-	var err error
-	var out []byte
-	for i := 0; i < constants.PullImageRetry; i++ {
-		out, err = runtime.exec.Command("docker", "pull", image).CombinedOutput()
-		if err == nil {
-			return nil
-		}
-	}
-	return errors.Wrapf(err, "output: %s, error", out)
-}
-
 // ImageExists checks to see if the image exists on the system
 func (runtime *CRIRuntime) ImageExists(image string) (bool, error) {
 	err := runtime.exec.Command("crictl", "-r", runtime.criSocket, "inspecti", image).Run()
 	return err == nil, nil
 }
 
-// ImageExists checks to see if the image exists on the system
-func (runtime *DockerRuntime) ImageExists(image string) (bool, error) {
-	err := runtime.exec.Command("docker", "inspect", image).Run()
-	return err == nil, nil
-}
-
 // detectCRISocketImpl is separated out only for test purposes, DON'T call it directly, use DetectCRISocket instead
-func detectCRISocketImpl(isSocket func(string) bool) (string, error) {
+func detectCRISocketImpl(isSocket func(string) bool, knownCRISockets []string) (string, error) {
 	foundCRISockets := []string{}
-	knownCRISockets := []string{
-		// Docker and containerd sockets are special cased below, hence not to be included here
-		"unix:///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) {
@@ -210,18 +133,20 @@ func detectCRISocketImpl(isSocket func(string) bool) (string, error) {
 
 	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
+		// Fall back to the default socket if no CRI is detected, we can error out later on if we need it
+		return constants.DefaultCRISocket, 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, ", "))
+		return "", errors.Errorf("Found multiple CRI endpoints on the host. Please define which one do you wish "+
+			"to use by setting the 'criSocket' field in the kubeadm configuration file: %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) {
-	return detectCRISocketImpl(isExistingSocket)
+	return detectCRISocketImpl(isExistingSocket, defaultKnownCRISockets)
 }

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

@@ -40,32 +40,25 @@ func TestNewContainerRuntime(t *testing.T) {
 		LookPathFunc: func(cmd string) (string, error) { return "", errors.Errorf("%s not found", cmd) },
 	}
 	cases := []struct {
-		name      string
-		execer    fakeexec.FakeExec
-		criSocket string
-		isDocker  bool
-		isError   bool
+		name    string
+		execer  fakeexec.FakeExec
+		isError bool
 	}{
-		{"valid: default cri socket", execLookPathOK, constants.DefaultDockerCRISocket, true, false},
-		{"valid: cri-o socket url", execLookPathOK, "unix:///var/run/crio/crio.sock", false, false},
-		{"invalid: no crictl", execLookPathErr, "unix:///var/run/crio/crio.sock", false, true},
+		{"valid: crictl present", execLookPathOK, false},
+		{"invalid: no crictl", execLookPathErr, true},
 	}
 
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
-			runtime, err := NewContainerRuntime(&tc.execer, tc.criSocket)
+			_, err := NewContainerRuntime(&tc.execer, "unix:///some/socket.sock")
 			if err != nil {
 				if !tc.isError {
-					t.Fatalf("unexpected NewContainerRuntime error. criSocket: %s, error: %v", tc.criSocket, err)
+					t.Fatalf("unexpected NewContainerRuntime error. error: %v", err)
 				}
 				return // expected error occurs, impossible to test runtime further
 			}
 			if tc.isError && err == nil {
-				t.Fatalf("unexpected NewContainerRuntime success. criSocket: %s", tc.criSocket)
-			}
-			isDocker := runtime.IsDocker()
-			if tc.isDocker != isDocker {
-				t.Fatalf("unexpected isDocker() result %v for the criSocket %s", isDocker, tc.criSocket)
+				t.Fatal("unexpected NewContainerRuntime success")
 			}
 		})
 	}
@@ -96,11 +89,6 @@ func TestIsRunning(t *testing.T) {
 		LookPathFunc:  func(cmd string) (string, error) { return "/usr/bin/crictl", nil },
 	}
 
-	dockerExecer := fakeexec.FakeExec{
-		CommandScript: genFakeActions(&fcmd, len(fcmd.CombinedOutputScript)),
-		LookPathFunc:  func(cmd string) (string, error) { return "/usr/bin/docker", nil },
-	}
-
 	cases := []struct {
 		name      string
 		criSocket string
@@ -109,8 +97,6 @@ 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", constants.DefaultDockerCRISocket, dockerExecer, false},
-		{"invalid: docker is not running", constants.DefaultDockerCRISocket, dockerExecer, true},
 	}
 
 	for _, tc := range cases {
@@ -150,7 +136,6 @@ 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", constants.DefaultDockerCRISocket, false},
 	}
 
 	for _, tc := range cases {
@@ -204,9 +189,6 @@ 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", constants.DefaultDockerCRISocket, []string{"k8s_c1", "k8s_c2", "k8s_c3"}, false},
-		{"invalid: docker rm failure", constants.DefaultDockerCRISocket, []string{"k8s_c1", "k8s_c2", "k8s_c3"}, true},
-		{"invalid: docker stop failure", constants.DefaultDockerCRISocket, []string{"k8s_c1", "k8s_c2", "k8s_c3"}, true},
 	}
 
 	for _, tc := range cases {
@@ -259,8 +241,6 @@ 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", constants.DefaultDockerCRISocket, "image1", false},
-		{"invalid: docker pull error", constants.DefaultDockerCRISocket, "image2", true},
 	}
 
 	for _, tc := range cases {
@@ -302,9 +282,7 @@ func TestImageExists(t *testing.T) {
 		result    bool
 	}{
 		{"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", constants.DefaultDockerCRISocket, "image1", false},
-		{"invalid: docker inspect failure", constants.DefaultDockerCRISocket, "image2", true},
+		{"invalid: CRI inspect failure", "unix:///var/run/crio/crio.sock", "image2", true},
 	}
 
 	for _, tc := range cases {
@@ -395,45 +373,22 @@ func TestDetectCRISocketImpl(t *testing.T) {
 		expectedSocket  string
 	}{
 		{
-			name:            "No existing sockets, use Docker",
+			name:            "No existing sockets, use default",
 			existingSockets: []string{},
 			expectedError:   false,
-			expectedSocket:  constants.DefaultDockerCRISocket,
+			expectedSocket:  constants.DefaultCRISocket,
 		},
 		{
 			name:            "One valid CRI socket leads to success",
-			existingSockets: []string{"unix:///var/run/crio/crio.sock"},
+			existingSockets: []string{"unix:///foo/bar.sock"},
 			expectedError:   false,
-			expectedSocket:  "unix:///var/run/crio/crio.sock",
+			expectedSocket:  "unix:///foo/bar.sock",
 		},
 		{
-			name:            "Correct Docker CRI socket is returned",
-			existingSockets: []string{"unix:///var/run/docker.sock"},
-			expectedError:   false,
-			expectedSocket:  constants.DefaultDockerCRISocket,
-		},
-		{
-			name: "CRI and Docker sockets lead to an error",
+			name: "Multiple CRI sockets lead to an error",
 			existingSockets: []string{
-				"unix:///var/run/docker.sock",
-				"unix:///var/run/crio/crio.sock",
-			},
-			expectedError: true,
-		},
-		{
-			name: "Docker and containerd lead to Docker being used",
-			existingSockets: []string{
-				"unix:///var/run/docker.sock",
-				"unix:///run/containerd/containerd.sock",
-			},
-			expectedError:  false,
-			expectedSocket: constants.DefaultDockerCRISocket,
-		},
-		{
-			name: "A couple of CRI sockets lead to an error",
-			existingSockets: []string{
-				"unix:///var/run/crio/crio.sock",
-				"unix:///run/containerd/containerd.sock",
+				"unix:///foo/bar.sock",
+				"unix:///foo/baz.sock",
 			},
 			expectedError: true,
 		},
@@ -447,9 +402,9 @@ func TestDetectCRISocketImpl(t *testing.T) {
 						return true
 					}
 				}
-
 				return false
-			})
+			}, test.existingSockets)
+
 			if (err != nil) != test.expectedError {
 				t.Fatalf("detectCRISocketImpl returned unexpected result\n\tExpected error: %t\n\tGot error: %t", test.expectedError, err != nil)
 			}

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

@@ -24,11 +24,6 @@ import (
 	"net/url"
 )
 
-const (
-	dockerSocket     = "unix:///var/run/docker.sock" // The Docker socket is not CRI compatible
-	containerdSocket = "unix:///run/containerd/containerd.sock"
-)
-
 // isExistingSocket checks if path exists and is domain socket
 func isExistingSocket(path string) bool {
 	u, err := url.Parse(path)

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

@@ -25,11 +25,6 @@ import (
 	winio "github.com/Microsoft/go-winio"
 )
 
-const (
-	dockerSocket     = "npipe:////./pipe/docker_engine"         // The Docker socket is not CRI compatible
-	containerdSocket = "npipe:////./pipe/containerd-containerd" // Proposed containerd named pipe for Windows
-)
-
 // isExistingSocket checks if path exists and is domain socket
 func isExistingSocket(path string) bool {
 	u, err := url.Parse(path)