added option for automatic kernel detection

internal/app/wwctl/kernel/imprt/main.go

@@ -14,13 +14,15 @@ import (
 )
 
 func CobraRunE(cmd *cobra.Command, args []string) error {
-
-	// Checking if container flag was set, then overwriting OptRoot
-	kernelVersion := args[0]
-	kernelName := kernelVersion
-	if len(args) > 1 {
-		kernelName = args[1]
+	if len(args) == 0 && !OptDetect {
+		wwlog.Printf(wwlog.ERROR, "the '--detect' flag is needed, if no kernel version is suppiled")
+		os.Exit(1)
 	}
+	if OptDetect && (OptRoot == "" || OptContainer == "") {
+		wwlog.Printf(wwlog.ERROR, "the '--detect flag needs the '--container' or '--root' flag")
+		os.Exit(1)
+	}
+	// Checking if container flag was set, then overwriting OptRoot
 	if OptContainer != "" {
 		if container.ValidSource(OptContainer) {
 			OptRoot = container.RootFsDir(OptContainer)
@@ -29,6 +31,24 @@ func CobraRunE(cmd *cobra.Command, args []string) error {
 			os.Exit(1)
 		}
 	}
+
+	var kernelVersion string
+	var err error
+	if len(args) > 0 {
+		kernelVersion = args[0]
+	} else {
+		kernelVersion, err = kernel.FindKernelVersion(OptRoot)
+		if err != nil {
+			wwlog.Printf(wwlog.ERROR, "could not detect kernel under %s\n", OptRoot)
+			os.Exit(1)
+		}
+	}
+	kernelName := kernelVersion
+	if len(args) > 1 {
+		kernelName = args[1]
+	} else if OptDetect && (OptContainer != "") {
+		kernelName = OptContainer
+	}
 	output, err := kernel.Build(kernelVersion, kernelName, OptRoot)
 	if err != nil {
 		wwlog.Printf(wwlog.ERROR, "Failed building kernel: %s\n", err)

internal/app/wwctl/kernel/imprt/root.go

@@ -10,17 +10,18 @@ import (
 var (
 	baseCmd = &cobra.Command{
 		DisableFlagsInUseLine: true,
-		Use:   "import [OPTIONS] KERNEL",
-		Short: "Import Kernel version into Warewulf",
-		Long: "This will import a boot KERNEL version from the control node into Warewulf",
-		RunE: CobraRunE,
-		Args: cobra.MinimumNArgs(1),
+		Use:                   "import [OPTIONS] KERNEL",
+		Short:                 "Import Kernel version into Warewulf",
+		Long:                  "This will import a boot KERNEL version from the control node into Warewulf",
+		RunE:                  CobraRunE,
+		Args:                  cobra.MinimumNArgs(0),
 	}
 	BuildAll     bool
 	ByNode       bool
 	SetDefault   bool
 	OptRoot      string
 	OptContainer string
+	OptDetect    bool
 )
 
 func init() {
@@ -36,6 +37,7 @@ func init() {
 	if err != nil {
 		log.Println(err)
 	}
+	baseCmd.PersistentFlags().BoolVarP(&OptDetect, "detect", "D", false, "Try to detect the kernel version in an automated way, needs the -C or -r option")
 }
 
 // GetRootCommand returns the root cobra.Command for the application.

internal/pkg/kernel/kernel.go

@@ -8,6 +8,8 @@ import (
 	"os"
 	"os/exec"
 	"path"
+	"path/filepath"
+	"regexp"
 
 	"github.com/pkg/errors"
 
@@ -228,3 +230,28 @@ func DeleteKernel(name string) error {
 	wwlog.Printf(wwlog.VERBOSE, "Removing path: %s\n", fullPath)
 	return os.RemoveAll(fullPath)
 }
+
+func FindKernelVersion(root string) (string, error) {
+	for _, searchPath := range kernelSearchPaths {
+		testPattern := fmt.Sprintf(path.Join(root, searchPath), `*`)
+		wwlog.Printf(wwlog.VERBOSE, "Looking for kernel version with pattern at: %s\n", testPattern)
+		potentialKernel, _ := filepath.Glob(testPattern)
+		if len(potentialKernel) == 0 {
+			continue
+		}
+		for _, foundKernel := range potentialKernel {
+			wwlog.Printf(wwlog.VERBOSE, "Parsing out kernel version for %s\n", foundKernel)
+			re := regexp.MustCompile(fmt.Sprintf(path.Join(root, searchPath), `([\w\d-\.]*)`))
+			version := re.FindAllStringSubmatch(foundKernel, -1)
+			if version == nil {
+				return "", fmt.Errorf("could not parse kernel version")
+			}
+			wwlog.Printf(wwlog.VERBOSE, "found kernel version %s\n", version)
+			return version[0][1], nil
+
+		}
+
+	}
+	return "", fmt.Errorf("could not find kernel version")
+
+}