Addresses issue #18724 "minikube mount does not work on 6.1.0-20-cloud-amd64" - Detect when OS does not support 9p

cmd/minikube/cmd/mount.go

@@ -186,6 +186,11 @@ var mountCmd = &cobra.Command{
 			cfg.Options[parts[0]] = parts[1]
 		}
 
+		if runtime.GOOS == "linux" && !detect.IsNinePSupported() {
+			exit.Message(reason.HostUnsupported, "The host does not support filesystem 9p.")
+
+		}
+
 		// An escape valve to allow future hackers to try NFS, VirtFS, or other FS types.
 		if !supportedFilesystems[cfg.Type] {
 			out.WarningT("{{.type}} is not yet a supported filesystem. We will try anyways!", out.V{"type": cfg.Type})

pkg/minikube/detect/detect_linux.go

@@ -19,6 +19,8 @@ limitations under the License.
 package detect
 
 import (
+	"os"
+	"path/filepath"
 	"runtime"
 
 	"golang.org/x/sys/unix"
@@ -54,3 +56,30 @@ func cgroupVersion() string {
 		return ""
 	}
 }
+
+func IsNinePSupported() bool {
+	// assume true from non-linux
+	if runtime.GOOS != "linux" {
+		return true
+	}
+	_, err := os.Stat(getModuleRoot() + "/kernel/fs/9p")
+	return err == nil
+}
+
+func getModuleRoot() string {
+	// assume true from non-linux
+	if runtime.GOOS != "linux" {
+		return ""
+	}
+	uname := unix.Utsname{}
+	if err := unix.Uname(&uname); err != nil {
+		return ""
+	}
+
+	i := 0
+	for ; uname.Release[i] != 0; i++ {
+		continue
+	}
+	return filepath.Join("/lib/modules", string(uname.Release[:i]))
+
+}

pkg/minikube/detect/detect_nonlinux.go

@@ -22,3 +22,8 @@ package detect
 func cgroupVersion() string {
 	return "v1"
 }
+
+// Assume 9p is supported by non linux apps
+func IsNinePSupported() bool {
+	return true
+}

pkg/minikube/reason/reason.go

@@ -288,6 +288,8 @@ var (
 	HostPurge = Kind{ID: "HOST_PURGE", ExitCode: ExHostError}
 	// minikube failed to persist profile config
 	HostSaveProfile = Kind{ID: "HOST_SAVE_PROFILE", ExitCode: ExHostConfig}
+	// Host doesn't support 9p
+	HostUnsupported = Kind{ID: "HOST_UNSUPPORTED", ExitCode: ExHostUnsupported}
 
 	// minikube could not find a provider for the selected driver
 	ProviderNotFound = Kind{ID: "PROVIDER_NOT_FOUND", ExitCode: ExProviderNotFound}