Warnings that k8s service may not work (#657)

Warnings that k8s service may not work (#657)
KU-1475

src/k8s/cmd/k8s/hooks.go

@@ -2,6 +2,7 @@ package k8s
 
 import (
 	cmdutil "github.com/canonical/k8s/cmd/util"
+
 	"github.com/spf13/cobra"
 )
 
@@ -34,3 +35,37 @@ func hookInitializeFormatter(env cmdutil.ExecutionEnvironment, format *string) f
 		}
 	}
 }
+
+// hookCheckLXD verifies the ownership of directories needed for Kubernetes to function.
+// If a potential issue is detected, it displays a warning to the user.
+func hookCheckLXD() func(*cobra.Command, []string) {
+	return func(cmd *cobra.Command, args []string) {
+		// pathsOwnershipCheck paths to validate root is the owner
+		var pathsOwnershipCheck = []string{"/sys", "/proc", "/dev/kmsg"}
+		inLXD, err := cmdutil.InLXDContainer()
+		if err != nil {
+			cmd.PrintErrf("Failed to check if running inside LXD container: %s", err.Error())
+			return
+		}
+		if inLXD {
+			var errMsgs []string
+			for _, pathToCheck := range pathsOwnershipCheck {
+				if err = cmdutil.ValidateRootOwnership(pathToCheck); err != nil {
+					errMsgs = append(errMsgs, err.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/")
+			}
+		}
+		return
+	}
+}

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]

src/k8s/cmd/util/hooks.go

@@ -0,0 +1,56 @@
+package cmdutil
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"syscall"
+)
+
+// getFileOwnerAndGroup retrieves the UID and GID of a file.
+func getFileOwnerAndGroup(filePath string) (uid, gid uint32, err error) {
+	// Get file info using os.Stat
+	fileInfo, err := os.Stat(filePath)
+	if err != nil {
+		return 0, 0, fmt.Errorf("error getting file info: %w", err)
+	}
+	// Convert the fileInfo.Sys() to syscall.Stat_t to access UID and GID
+	stat, ok := fileInfo.Sys().(*syscall.Stat_t)
+	if !ok {
+		return 0, 0, fmt.Errorf("failed to cast to syscall.Stat_t")
+	}
+	// Return the UID and GID
+	return stat.Uid, stat.Gid, nil
+}
+
+// ValidateRootOwnership checks if the specified path is owned by the root user and root group.
+func ValidateRootOwnership(path string) (err error) {
+	UID, GID, err := getFileOwnerAndGroup(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 a lxd container.
+func InLXDContainer() (isLXD bool, err error) {
+	initialProcessEnvironmentVariables := "/proc/1/environ"
+	content, err := os.ReadFile(initialProcessEnvironmentVariables)
+	if err != nil {
+		// if the permission to file is missing we still want to display info about lxd
+		if os.IsPermission(err) {
+			return true, fmt.Errorf("cannnot access %s to check if runing in LXD container: %w", initialProcessEnvironmentVariables, err)
+		}
+		return false, fmt.Errorf("cannnot read %s to check if runing in LXD container: %w", initialProcessEnvironmentVariables, err)
+	}
+	if strings.Contains(string(content), "container=lxc") {
+		return true, nil
+	}
+	return false, nil
+}