Add --dry-run option to start

cmd/minikube/cmd/start.go

@@ -116,6 +116,7 @@ const (
 	hostDNSResolver       = "host-dns-resolver"
 	waitUntilHealthy      = "wait"
 	force                 = "force"
+	dryRun                = "dry-run"
 	interactive           = "interactive"
 	waitTimeout           = "wait-timeout"
 	nativeSSH             = "native-ssh"
@@ -158,6 +159,7 @@ func initMinikubeFlags() {
 
 	startCmd.Flags().Bool(force, false, "Force minikube to perform possibly dangerous operations")
 	startCmd.Flags().Bool(interactive, true, "Allow user prompts for more information")
+	startCmd.Flags().Bool(dryRun, false, "dry-run mode. Validates configuration, but does does not mutate system state")
 
 	startCmd.Flags().Int(cpus, 2, "Number of CPUs allocated to the minikube VM.")
 	startCmd.Flags().String(memory, defaultMemorySize, "Amount of RAM allocated to the minikube VM (format: <number>[<unit>], where unit = b, k, m or g).")
@@ -306,14 +308,22 @@ func runStart(cmd *cobra.Command, args []string) {
 	validateUser(driverName)
 
 	// Download & update the driver, even in --download-only mode
-	updateDriver(driverName)
+	if !viper.GetBool(dryRun) {
+		updateDriver(driverName)
+	}
 
 	k8sVersion, isUpgrade := getKubernetesVersion(existing)
 	config, err := generateCfgFromFlags(cmd, k8sVersion, driverName)
 	if err != nil {
 		exit.WithError("Failed to generate config", err)
 	}
 
+	// This is about as far as we can go without overwriting config files
+	if viper.GetBool(dryRun) {
+		out.T(out.DryRun, `dry-run validation complete!`)
+		return
+	}
+
 	cacheISO(&config, driverName)
 
 	if viper.GetBool(nativeSSH) {
@@ -755,7 +765,7 @@ func validateDiskSize() {
 func validateMemorySize() {
 	memorySizeMB := pkgutil.CalculateSizeInMB(viper.GetString(memory))
 	if memorySizeMB < pkgutil.CalculateSizeInMB(minimumMemorySize) && !viper.GetBool(force) {
-		exit.UsageT("Requested memory allocation {{.requested_size}} is less than the minimum allowed of {{.minimum_size}}", out.V{"requested_size": memorySizeMB, "minimum_size": pkgutil.CalculateSizeInMB(minimumMemorySize)})
+		exit.WithCodeT(exit.Config, "Requested memory allocation {{.requested_size}} is less than the minimum allowed of {{.minimum_size}}", out.V{"requested_size": memorySizeMB, "minimum_size": pkgutil.CalculateSizeInMB(minimumMemorySize)})
 	}
 	if memorySizeMB < pkgutil.CalculateSizeInMB(defaultMemorySize) && !viper.GetBool(force) {
 		out.T(out.Notice, "Requested memory allocation ({{.memory}}MB) is less than the default memory allocation of {{.default_memorysize}}MB. Beware that minikube might not work correctly or crash unexpectedly.",

pkg/minikube/out/style.go

@@ -113,6 +113,7 @@ var styles = map[StyleEnum]style{
 	Unmount:          {Prefix: "🔥  "},
 	MountOptions:     {Prefix: "💾  "},
 	Fileserver:       {Prefix: "🚀  ", OmitNewline: true},
+	DryRun:           {Prefix: "🏜️   "},
 }
 
 // Add a prefix to a string

pkg/minikube/out/style_enum.go

@@ -84,4 +84,5 @@ const (
 	Empty
 	Workaround
 	Sparkle
+	DryRun
 )

test/integration/functional_test.go

@@ -92,6 +92,7 @@ func TestFunctional(t *testing.T) {
 			{"ConfigCmd", validateConfigCmd},
 			{"DashboardCmd", validateDashboardCmd},
 			{"DNS", validateDNS},
+			{"DryRun", validateDryRun},
 			{"StatusCmd", validateStatusCmd},
 			{"LogsCmd", validateLogsCmd},
 			{"MountCmd", validateMountCmd},
@@ -309,6 +310,32 @@ func validateDNS(ctx context.Context, t *testing.T, profile string) {
 	}
 }
 
+// validateDryRun asserts that the dry-run mode quickly exits with the right code
+func validateDryRun(ctx context.Context, t *testing.T, profile string) {
+	// dry-run mode should always be able to finish quickly
+	mctx, cancel := context.WithTimeout(ctx, 2*time.Second)
+	defer cancel()
+
+	// Too little memory!
+	startArgs := append([]string{"start", "-p", profile, "--dry-run", "--memory", "250MB"}, StartArgs()...)
+	c := exec.CommandContext(mctx, Target(), startArgs...)
+	rr, err := Run(t, c)
+
+	wantCode := 78 // exit.Config
+	if rr.ExitCode != wantCode {
+		t.Errorf("dry-run(250MB) exit code = %d, wanted = %d: %v", rr.ExitCode, wantCode, err)
+	}
+
+	dctx, cancel := context.WithTimeout(ctx, 2*time.Second)
+	defer cancel()
+	startArgs = append([]string{"start", "-p", profile, "--dry-run"}, StartArgs()...)
+	c = exec.CommandContext(dctx, Target(), startArgs...)
+	rr, err = Run(t, c)
+	if rr.ExitCode != 0 || err != nil {
+		t.Errorf("dry-run exit code = %d, wanted = %d: %v", rr.ExitCode, 0, err)
+	}
+}
+
 // validateCacheCmd tests functionality of cache command (cache add, delete, list)
 func validateCacheCmd(ctx context.Context, t *testing.T, profile string) {
 	if NoneDriver() {