Warnings that k8s service may not work

src/k8s/cmd/k8s/hooks.go

@@ -1,10 +1,22 @@
 package k8s
 
 import (
+	"fmt"
+	"os"
+	"strings"
+	"syscall"
+
 	cmdutil "github.com/canonical/k8s/cmd/util"
+
 	"github.com/spf13/cobra"
 )
 
+// initialProcessEnvironmentVariables environment variables of initial process
+const initialProcessEnvironmentVariables = "/proc/1/environ"
+
+// pathsOwnershipCheck paths to validate root is the ownership
+var pathsOwnershipCheck = []string{"/sys", "/proc", "/dev/kmsg"}
+
 func chainPreRunHooks(hooks ...func(*cobra.Command, []string)) func(*cobra.Command, []string) {
 	return func(cmd *cobra.Command, args []string) {
 		for _, hook := range hooks {
@@ -34,3 +46,80 @@ func hookInitializeFormatter(env cmdutil.ExecutionEnvironment, format *string) f
 		}
 	}
 }
+
+// hookCheckLXD checks ownership of directories required for k8s to run.
+// If potential issue found pops up warning for user.
+func hookCheckLXD() func(*cobra.Command, []string) {
+	return func(cmd *cobra.Command, args []string) {
+		if lxd, err := inLXDContainer(); lxd {
+			var errMsgs []string
+			for _, pathToCheck := range pathsOwnershipCheck {
+				if err2 := validateRootOwnership(pathToCheck); err2 != nil {
+					errMsgs = append(errMsgs, err2.Error())
+				}
+			}
+			if len(errMsgs) > 0 {
+				if debug, _ := cmd.Flags().GetBool("debug"); debug {
+					cmd.PrintErrln("Warning: When validating required resources potential issues found:")
+					for _, errMsg := range errMsgs {
+						cmd.PrintErrln("\t", errMsg)
+					}
+				}
+				cmd.PrintErrln("The lxc profile for Canonical Kubernetes might be missing.")
+				cmd.PrintErrln("For running k8s inside LXD container refer to " +
+					"https://documentation.ubuntu.com/canonical-kubernetes/latest/snap/howto/install/lxd/")
+			}
+		} else if err != nil {
+			cmd.PrintErrf(err.Error())
+		}
+	}
+}
+
+// getOwnership given path of file returns UID, GID and error.
+func getOwnership(path string) (int, int, error) {
+	info, err := os.Stat(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return 0, 0, fmt.Errorf("%s do not exist", path)
+		} else {
+			return 0, 0, err
+		}
+	}
+	if stat, ok := info.Sys().(*syscall.Stat_t); ok {
+		return int(stat.Uid), int(stat.Gid), nil
+	} else {
+		return 0, 0, fmt.Errorf("cannot access %s", path)
+	}
+}
+
+// validateRootOwnership checks if given path owner root and root group.
+func validateRootOwnership(path string) error {
+	UID, GID, err := getOwnership(path)
+	if err != nil {
+		return err
+	}
+	if UID != 0 {
+		return fmt.Errorf("owner of %s is user with UID %d expected 0", path, UID)
+	}
+	if GID != 0 {
+		return fmt.Errorf("owner of %s is group with GID %d expected 0", path, GID)
+	}
+	return nil
+}
+
+// inLXDContainer checks if k8s runs in lxd container.
+func inLXDContainer() (bool, error) {
+	content, err := os.ReadFile(initialProcessEnvironmentVariables)
+	if err != nil {
+		// if permission to file is missing we still want to display info about lxd
+		if os.IsPermission(err) {
+			return true, err
+		}
+		return false, err
+	}
+	env := string(content)
+	if strings.Contains(env, "container=lxc") {
+		return true, nil
+	}
+	return false, nil
+}

src/k8s/cmd/k8s/k8s_bootstrap.go

@@ -45,7 +45,7 @@ func newBootstrapCmd(env cmdutil.ExecutionEnvironment) *cobra.Command {
 		Use:    "bootstrap",
 		Short:  "Bootstrap a new Kubernetes cluster",
 		Long:   "Generate certificates, configure service arguments and start the Kubernetes services.",
-		PreRun: chainPreRunHooks(hookRequireRoot(env), hookInitializeFormatter(env, &opts.outputFormat)),
+		PreRun: chainPreRunHooks(hookRequireRoot(env), hookInitializeFormatter(env, &opts.outputFormat), hookCheckLXD()),
 		Run: func(cmd *cobra.Command, args []string) {
 			if opts.interactive && opts.configFile != "" {
 				cmd.PrintErrln("Error: --interactive and --file flags cannot be set at the same time.")

src/k8s/cmd/k8s/k8s_join_cluster.go

@@ -32,7 +32,7 @@ func newJoinClusterCmd(env cmdutil.ExecutionEnvironment) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:    "join-cluster <join-token>",
 		Short:  "Join a cluster using the provided token",
-		PreRun: chainPreRunHooks(hookRequireRoot(env), hookInitializeFormatter(env, &opts.outputFormat)),
+		PreRun: chainPreRunHooks(hookRequireRoot(env), hookInitializeFormatter(env, &opts.outputFormat), hookCheckLXD()),
 		Args:   cmdutil.ExactArgs(env, 1),
 		Run: func(cmd *cobra.Command, args []string) {
 			token := args[0]