add overlay file deletion support

Signed-off-by: jason yang <jasonyangshadow@gmail.com>

internal/pkg/overlay/overlay.go

@@ -22,9 +22,7 @@ import (
 	"github.com/warewulf/warewulf/internal/pkg/wwlog"
 )
 
-var (
-	ErrDoesNotExist = fmt.Errorf("overlay does not exist")
-)
+var ErrDoesNotExist = fmt.Errorf("overlay does not exist")
 
 // Overlay represents an overlay directory path.
 type Overlay string
@@ -102,6 +100,69 @@ func (overlay Overlay) IsDistributionOverlay() bool {
 	return path.Dir(overlay.Path()) == config.Get().Paths.DistributionOverlaydir()
 }
 
+// DeleteFile deletes a file or the entire overlay directory.
+// If the file belongs to a distribution overlay, it will be cloned to a site overlay
+// before deletion.
+func (overlay Overlay) DeleteFile(filePath string, force, cleanup bool) error {
+	wwlog.Info("Deleting file %s from overlay %s, force: %v, cleanup: %v", filePath, overlay.Name(), force, cleanup)
+	if filePath == "" {
+		if force {
+			err := os.RemoveAll(overlay.Path())
+			if err != nil {
+				return fmt.Errorf("failed to delete overlay forcely: %w", err)
+			}
+		} else {
+			err := os.Remove(overlay.Path())
+			if err != nil {
+				return fmt.Errorf("failed to delete overlay: %w", err)
+			}
+		}
+	} else {
+		if overlay.IsDistributionOverlay() {
+			siteOverlay, err := overlay.CloneSiteOverlay()
+			if err != nil {
+				return fmt.Errorf("failed to clone distribution overlay '%s' to site overlay: %w", overlay.Name(), err)
+			}
+			// replace the overlay with newly creatd siteOverlay
+			overlay = siteOverlay
+		}
+
+		fullPath := overlay.File(filePath)
+		if !util.IsFile(fullPath) {
+			return fmt.Errorf("file %s does not exist in overlay %s", filePath, overlay.Name())
+		}
+
+		if force {
+			if err := os.RemoveAll(fullPath); err != nil {
+				return fmt.Errorf("failed to delete file %s from overlay %s: %w", filePath, overlay.Name(), err)
+			}
+		} else {
+			if err := os.Remove(fullPath); err != nil {
+				return fmt.Errorf("failed to delete file %s from overlay %s: %w", filePath, overlay.Name(), err)
+			}
+		}
+
+		if cleanup {
+			// cleanup the empty parents
+			i := path.Dir(fullPath)
+			for i != overlay.Rootfs() {
+				wwlog.Debug("Evaluating directory to remove: %s", i)
+				err := os.Remove(i)
+				if err != nil {
+					// if the directory is not empty, we stop here
+					if !os.IsNotExist(err) {
+						wwlog.Debug("Could not remove directory %s: %v", i, err)
+					}
+					break
+				}
+				wwlog.Debug("Removed empty directory: %s", i)
+				i = path.Dir(i)
+			}
+		}
+	}
+	return nil
+}
+
 func BuildAllOverlays(nodes []node.Node, allNodes []node.Node, workerCount int) error {
 	nodeChan := make(chan node.Node, len(nodes))
 	errChan := make(chan error, len(nodes)*2)
@@ -196,7 +257,7 @@ func BuildHostOverlay() error {
 	if err != nil {
 		return fmt.Errorf("could not build host overlay: %w ", err)
 	}
-	if !(stats.Mode() == os.FileMode(0750|os.ModeDir) || stats.Mode() == os.FileMode(0700|os.ModeDir)) {
+	if !(stats.Mode() == os.FileMode(0o750|os.ModeDir) || stats.Mode() == os.FileMode(0o700|os.ModeDir)) {
 		wwlog.SecWarn("Permissions of host overlay dir %s are %s (750 is considered as secure)", hostdir, stats.Mode())
 	}
 	registry, err := node.New()
@@ -257,7 +318,7 @@ func BuildOverlay(nodeConf node.Node, allNodes []node.Node, context string, over
 	overlayImage := OverlayImage(nodeConf.Id(), context, overlayNames)
 	overlayImageDir := path.Dir(overlayImage)
 
-	err := os.MkdirAll(overlayImageDir, 0750)
+	err := os.MkdirAll(overlayImageDir, 0o750)
 	if err != nil {
 		return fmt.Errorf("failed to create directory for %s: %s: %w", name, overlayImageDir, err)
 	}
@@ -292,8 +353,10 @@ func BuildOverlay(nodeConf node.Node, allNodes []node.Node, context string, over
 	return err
 }
 
-var regFile *regexp.Regexp
-var regLink *regexp.Regexp
+var (
+	regFile *regexp.Regexp
+	regLink *regexp.Regexp
+)
 
 func init() {
 	regFile = regexp.MustCompile(`.*{{\s*/\*\s*file\s*["'](.*)["']\s*\*/\s*}}.*`)
@@ -450,7 +513,6 @@ func BuildOverlayIndir(nodeData node.Node, allNodes []node.Node, overlayNames []
 
 			return nil
 		})
-
 		if err != nil {
 			return fmt.Errorf("failed to build overlay image directory: %w", err)
 		}
@@ -471,7 +533,6 @@ func CarefulWriteBuffer(destFile string, buffer bytes.Buffer, backupFile bool, p
 				return fmt.Errorf("failed to create backup: %s -> %s.wwbackup %w", destFile, destFile, err)
 			}
 		}
-
 	}
 	w, err := os.OpenFile(destFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
 	if err != nil {
@@ -491,7 +552,8 @@ func RenderTemplateFile(fileName string, data TemplateStruct) (
 	buffer bytes.Buffer,
 	backupFile bool,
 	writeFile bool,
-	err error) {
+	err error,
+) {
 	backupFile = true
 	writeFile = true
 	// Build our FuncMap