Add --no-kubernetes flag to start minikube without kubernetes

cmd/minikube/cmd/config/profile_list.go

@@ -25,6 +25,7 @@ import (
 
 	"k8s.io/minikube/pkg/minikube/bootstrapper/bsutil/kverify"
 	"k8s.io/minikube/pkg/minikube/config"
+	"k8s.io/minikube/pkg/minikube/constants"
 	"k8s.io/minikube/pkg/minikube/driver"
 	"k8s.io/minikube/pkg/minikube/exit"
 	"k8s.io/minikube/pkg/minikube/machine"
@@ -164,7 +165,11 @@ func profilesToTableData(profiles []*config.Profile) [][]string {
 			exit.Error(reason.GuestCpConfig, "error getting primary control plane", err)
 		}
 
-		data = append(data, []string{p.Name, p.Config.Driver, p.Config.KubernetesConfig.ContainerRuntime, cp.IP, strconv.Itoa(cp.Port), p.Config.KubernetesConfig.KubernetesVersion, p.Status, strconv.Itoa(len(p.Config.Nodes))})
+		k8sVersion := p.Config.KubernetesConfig.KubernetesVersion
+		if k8sVersion == constants.NoKubernetesVersion { // for --no-kubernetes flag
+			k8sVersion = "N/A"
+		}
+		data = append(data, []string{p.Name, p.Config.Driver, p.Config.KubernetesConfig.ContainerRuntime, cp.IP, strconv.Itoa(cp.Port), k8sVersion, p.Status, strconv.Itoa(len(p.Config.Nodes))})
 	}
 	return data
 }

cmd/minikube/cmd/start.go

@@ -32,6 +32,7 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/Delta456/box-cli-maker/v2"
 	"github.com/blang/semver/v4"
 	"github.com/docker/machine/libmachine/ssh"
 	"github.com/google/go-containerregistry/pkg/authn"
@@ -432,6 +433,17 @@ func displayEnviron(env []string) {
 }
 
 func showKubectlInfo(kcs *kubeconfig.Settings, k8sVersion string, machineName string) error {
+	if k8sVersion == constants.NoKubernetesVersion {
+		register.Reg.SetStep(register.Done)
+		out.Step(style.Ready, "Done! minikube is ready without Kubernetes!")
+		out.BoxedWithConfig(box.Config{Py: 1, Px: 4, Type: "Round", Color: "Green"}, style.Tip, "Things to try without Kubernetes ...", `- "minikube ssh" to SSH into minikube's node.
+- "minikube docker-env" to point your docker-cli to the docker inside minikube.
+- "minikube image" to build images without docker`)
+		return nil
+	}
+
+	// here are some ideas to do without Kubernetes:
+
 	// To be shown at the end, regardless of exit path
 	defer func() {
 		register.Reg.SetStep(register.Done)
@@ -1463,16 +1475,14 @@ func autoSetDriverOptions(cmd *cobra.Command, drvName string) (err error) {
 // validateKubernetesVersion ensures that the requested version is reasonable
 func validateKubernetesVersion(old *config.ClusterConfig) {
 	nvs, _ := semver.Make(strings.TrimPrefix(getKubernetesVersion(old), version.VersionPrefix))
+	oldestVersion := semver.MustParse(strings.TrimPrefix(constants.OldestKubernetesVersion, version.VersionPrefix))
+	defaultVersion := semver.MustParse(strings.TrimPrefix(constants.DefaultKubernetesVersion, version.VersionPrefix))
+	zeroVersion := semver.MustParse(strings.TrimPrefix(constants.NoKubernetesVersion, version.VersionPrefix))
 
-	oldestVersion, err := semver.Make(strings.TrimPrefix(constants.OldestKubernetesVersion, version.VersionPrefix))
-	if err != nil {
-		exit.Message(reason.InternalSemverParse, "Unable to parse oldest Kubernetes version from constants: {{.error}}", out.V{"error": err})
-	}
-	defaultVersion, err := semver.Make(strings.TrimPrefix(constants.DefaultKubernetesVersion, version.VersionPrefix))
-	if err != nil {
-		exit.Message(reason.InternalSemverParse, "Unable to parse default Kubernetes version from constants: {{.error}}", out.V{"error": err})
+	if nvs.Equals(zeroVersion) {
+		klog.Infof("No Kuberentes version set for minikube, setting Kubernetes version to %s", constants.NoKubernetesVersion)
+		return
 	}
-
 	if nvs.LT(oldestVersion) {
 		out.WarningT("Specified Kubernetes version {{.specified}} is less than the oldest supported version: {{.oldest}}", out.V{"specified": nvs, "oldest": constants.OldestKubernetesVersion})
 		if !viper.GetBool(force) {
@@ -1519,6 +1529,11 @@ func isBaseImageApplicable(drv string) bool {
 }
 
 func getKubernetesVersion(old *config.ClusterConfig) string {
+	if viper.GetBool(noKubernetes) {
+		klog.Infof("No Kubernetes flag is set, setting Kubernetes version to %s", constants.NoKubernetesVersion)
+		viper.Set(kubernetesVersion, constants.NoKubernetesVersion)
+	}
+
 	paramVersion := viper.GetString(kubernetesVersion)
 
 	// try to load the old version first if the user didn't specify anything

cmd/minikube/cmd/start_flags.go

@@ -55,6 +55,7 @@ const (
 	nfsSharesRoot           = "nfs-shares-root"
 	nfsShare                = "nfs-share"
 	kubernetesVersion       = "kubernetes-version"
+	noKubernetes            = "no-kubernetes"
 	hostOnlyCIDR            = "host-only-cidr"
 	containerRuntime        = "container-runtime"
 	criSocket               = "cri-socket"
@@ -164,6 +165,7 @@ func initMinikubeFlags() {
 	startCmd.Flags().Bool(installAddons, true, "If set, install addons. Defaults to true.")
 	startCmd.Flags().IntP(nodes, "n", 1, "The number of nodes to spin up. Defaults to 1.")
 	startCmd.Flags().Bool(preload, true, "If set, download tarball of preloaded images if available to improve start time. Defaults to true.")
+	startCmd.Flags().Bool(noKubernetes, false, "If set, minikube VM/container will start without starting or configuring Kubernetes. (only works on new clusters)")
 	startCmd.Flags().Bool(deleteOnFailure, false, "If set, delete the current cluster if start fails and try again. Defaults to false.")
 	startCmd.Flags().Bool(forceSystemd, false, "If set, force the container runtime to use systemd as cgroup manager. Defaults to false.")
 	startCmd.Flags().StringP(network, "", "", "network to run minikube with. Now it is used by docker/podman and KVM drivers. If left empty, minikube will create a new network.")

pkg/minikube/constants/constants.go

@@ -40,6 +40,9 @@ const (
 	NewestKubernetesVersion = "v1.22.4-rc.0"
 	// OldestKubernetesVersion is the oldest Kubernetes version to test against
 	OldestKubernetesVersion = "v1.14.0"
+	// NoKubernetesVersion is the version used when users does NOT want to install kubernetes
+	NoKubernetesVersion = "v0.0.0"
+
 	// DefaultClusterName is the default nane for the k8s cluster
 	DefaultClusterName = "minikube"
 	// DockerDaemonPort is the port Docker daemon listening inside a minikube node (vm or container).

pkg/minikube/node/start.go

@@ -88,6 +88,10 @@ type Starter struct {
 
 // Start spins up a guest and starts the Kubernetes node.
 func Start(starter Starter, apiServer bool) (*kubeconfig.Settings, error) {
+	var kcs *kubeconfig.Settings
+	if starter.Node.KubernetesVersion == constants.NoKubernetesVersion { // do not bootstrap cluster if --no-kubernetes
+		return kcs, config.Write(viper.GetString(config.ProfileName), starter.Cfg)
+	}
 	// wait for preloaded tarball to finish downloading before configuring runtimes
 	waitCacheRequiredImages(&cacheGroup)
 
@@ -115,7 +119,6 @@ func Start(starter Starter, apiServer bool) (*kubeconfig.Settings, error) {
 	}
 
 	var bs bootstrapper.Bootstrapper
-	var kcs *kubeconfig.Settings
 	if apiServer {
 		// Must be written before bootstrap, otherwise health checks may flake due to stale IP
 		kcs = setupKubeconfig(starter.Host, starter.Cfg, starter.Node, starter.Cfg.Name)
@@ -286,11 +289,16 @@ func joinCluster(starter Starter, cpBs bootstrapper.Bootstrapper, bs bootstrappe
 func Provision(cc *config.ClusterConfig, n *config.Node, apiServer bool, delOnFail bool) (command.Runner, bool, libmachine.API, *host.Host, error) {
 	register.Reg.SetStep(register.StartingNode)
 	name := config.MachineName(*cc, *n)
-	if apiServer {
-		out.Step(style.ThumbsUp, "Starting control plane node {{.name}} in cluster {{.cluster}}", out.V{"name": name, "cluster": cc.Name})
-	} else {
-		out.Step(style.ThumbsUp, "Starting node {{.name}} in cluster {{.cluster}}", out.V{"name": name, "cluster": cc.Name})
+
+	startingPhrase := "Starting control plane node"
+	if !apiServer {
+		startingPhrase = "Starting worker node"
 	}
+	if cc.KubernetesConfig.KubernetesVersion == constants.NoKubernetesVersion {
+		startingPhrase = "Starting minikube without Kubernetes"
+	}
+
+	out.Step(style.ThumbsUp, "{{.nodeName}} {{.name}} in cluster {{.cluster}}", out.V{"nodeName": startingPhrase, "name": name, "cluster": cc.Name})
 
 	if driver.IsKIC(cc.Driver) {
 		beginDownloadKicBaseImage(&kicGroup, cc, viper.GetBool("download-only"))

pkg/minikube/out/out.go

@@ -134,13 +134,13 @@ func BoxedErr(format string, a ...V) {
 }
 
 // BoxedWithConfig writes a templated message in a box with customized style config to stdout
-func BoxedWithConfig(cfg box.Config, st style.Enum, title string, format string, a ...V) {
+func BoxedWithConfig(cfg box.Config, st style.Enum, title string, text string, a ...V) {
 	if st != style.None {
 		title = Sprintf(st, title)
 	}
 	// need to make sure no newlines are in the title otherwise box-cli-maker panics
 	title = strings.ReplaceAll(title, "\n", "")
-	boxedCommon(String, cfg, title, format, a...)
+	boxedCommon(String, cfg, title, text, a...)
 }
 
 // Sprintf is used for returning the string (doesn't write anything)

test/integration/no_kubernetes.go

@@ -0,0 +1,135 @@
+//go:build integration
+// +build integration
+
+/*
+Copyright 2021 The Kubernetes Authors All rights reserved.
+
+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 integration
+
+import (
+	"context"
+	"os/exec"
+	"strings"
+	"testing"
+)
+
+// TestNoKubernetes tests starting minikube without Kubernetes,
+// for use cases where user only needs to use the container runtime (docker, containerd, crio) inside minikube
+func TestNoKubernetes(t *testing.T) {
+	MaybeParallel(t)
+
+	type validateFunc func(context.Context, *testing.T, string)
+	profile := UniqueProfileName("NoKubernetes")
+	ctx, cancel := context.WithTimeout(context.Background(), Minutes(5))
+	defer Cleanup(t, profile, cancel)
+
+	// Serial tests
+	t.Run("serial", func(t *testing.T) {
+		tests := []struct {
+			name      string
+			validator validateFunc
+		}{
+			{"Start", validateStartNoK8S},
+			{"VerifyK8sNotRunning", validateK8SNotRunning},
+			{"ProfileList", validateProfileListNoK8S},
+			{"Stop", validateStopNoK8S},
+			{"StartNoArgs", validateStartNoArgs},
+			{"VerifyK8sNotRunningSecond", validateK8SNotRunning},
+		}
+
+		for _, tc := range tests {
+			tc := tc
+
+			if ctx.Err() == context.DeadlineExceeded {
+				t.Fatalf("Unable to run more tests (deadline exceeded)")
+			}
+
+			t.Run(tc.name, func(t *testing.T) {
+				tc.validator(ctx, t, profile)
+				if t.Failed() && *postMortemLogs {
+					PostMortemLogs(t, profile)
+				}
+			})
+		}
+	})
+}
+
+// validateStartNoK8S starts a minikube cluster without kubernetes started/configured
+func validateStartNoK8S(ctx context.Context, t *testing.T, profile string) {
+	defer PostMortemLogs(t, profile)
+
+	args := append([]string{"start", "-p", profile, "--no-kubernetes"}, StartArgs()...)
+	rr, err := Run(t, exec.CommandContext(ctx, Target(), args...))
+	if err != nil {
+		t.Fatalf("failed to start minikube with args: %q : %v", rr.Command(), err)
+	}
+}
+
+// validateK8SNotRunning validates that there is no kubernetes running inside minikube
+func validateK8SNotRunning(ctx context.Context, t *testing.T, profile string) {
+	defer PostMortemLogs(t, profile)
+
+	args := []string{"ssh", "-p", profile, "sudo systemctl is-active --quiet service kubelet"}
+	rr, err := Run(t, exec.CommandContext(ctx, Target(), args...))
+	if err == nil {
+		t.Fatalf("Expected Kubelet not to be running and but it is running : %q : %v", rr.Command(), err)
+	}
+}
+
+// validateStopNoK8S validates that minikube is stopped after a --no-kubernetes start
+func validateStopNoK8S(ctx context.Context, t *testing.T, profile string) {
+	defer PostMortemLogs(t, profile)
+
+	args := []string{"stop", "-p", profile}
+	rr, err := Run(t, exec.CommandContext(ctx, Target(), args...))
+	if err != nil {
+		t.Fatalf("Failed to stop minikube %q : %v", rr.Command(), err)
+	}
+}
+
+// validateProfileListNoK8S validates that profile list works with --no-kubernetes
+func validateProfileListNoK8S(ctx context.Context, t *testing.T, profile string) {
+	defer PostMortemLogs(t, profile)
+
+	args := []string{"profile", "list"}
+	rr, err := Run(t, exec.CommandContext(ctx, Target(), args...))
+	if err != nil {
+		t.Fatalf("Profile list failed : %q : %v", rr.Command(), err)
+	}
+
+	if !strings.Contains(rr.Output(), "N/A") {
+		t.Fatalf("expected N/A in the profile list for kubernetes version but got : %q : %v", rr.Command(), rr.Output())
+	}
+
+	args = []string{"profile", "list", "--output=json"}
+	rr, err = Run(t, exec.CommandContext(ctx, Target(), args...))
+	if err != nil {
+		t.Fatalf("Profile list --output=json failed : %q : %v", rr.Command(), err)
+	}
+
+}
+
+// validateStartNoArgs valides that minikube start with no args works
+func validateStartNoArgs(ctx context.Context, t *testing.T, profile string) {
+	defer PostMortemLogs(t, profile)
+
+	args := append([]string{"start", "-p", profile, "--no-kubernetes"}, StartArgs()...)
+	rr, err := Run(t, exec.CommandContext(ctx, Target(), args...))
+	if err != nil {
+		t.Fatalf("failed to start minikube with args: %q : %v", rr.Command(), err)
+	}
+
+}