add -k arg for keeping the image filesystem owner

cmd/root.go

@@ -47,6 +47,7 @@ var cacheDir string
 var LogLevel string
 var format string
 
+var keepOwner bool
 const containerDiffEnvCacheDir = "CONTAINER_DIFF_CACHEDIR"
 
 type validatefxn func(args []string) error
@@ -147,7 +148,7 @@ func getImage(imageName string) (pkgutil.Image, error) {
 return pkgutil.Image{}, err
 }
 }
-return pkgutil.GetImage(imageName, includeLayers(), cachePath)
+return pkgutil.GetImage(imageName, includeLayers(), keepOwner, cachePath)
 }
 
 func getCacheDir(imageName string) (string, error) {
@@ -239,6 +240,7 @@ func addSharedFlags(cmd *cobra.Command) {
 cmd.Flags().BoolVarP(&save, "save", "s", false, "Set this flag to save rather than remove the final image filesystems on exit.")
 cmd.Flags().BoolVarP(&util.SortSize, "order", "o", false, "Set this flag to sort any file/package results by descending size. Otherwise, they will be sorted by name.")
 cmd.Flags().BoolVarP(&noCache, "no-cache", "n", false, "Set this to force retrieval of image filesystem on each run.")
+cmd.Flags().BoolVarP(&keepOwner, "keep-owner", "k", false, "Set this to keep the owner of image filesystem. Make sure you are a root user for setting this value.")
 cmd.Flags().StringVarP(&cacheDir, "cache-dir", "c", "", "cache directory base to create .container-diff (default is $HOME).")
 cmd.Flags().StringVarP(&outputFile, "output", "w", "", "output file to write to (default writes to the screen).")
 cmd.Flags().BoolVar(&forceWrite, "force", false, "force overwrite output file, if exists already.")

pkg/util/image_utils.go

@@ -69,13 +69,13 @@ type ImageHistoryItem struct {
 // GetImageForName retrieves an image by name alone.
 // It does not return layer information, or respect caching.
 func GetImageForName(imageName string) (Image, error) {
-return GetImage(imageName, false, "")
+return GetImage(imageName, false, false, "")
 }
 
 // GetImage infers the source of an image and retrieves a v1.Image reference to it.
 // Once a reference is obtained, it attempts to unpack the v1.Image's reader's contents
 // into a temp directory on the local filesystem.
-func GetImage(imageName string, includeLayers bool, cacheDir string) (Image, error) {
+func GetImage(imageName string, includeLayers, keepOwner bool, cacheDir string) (Image, error) {
 logrus.Infof("retrieving image: %s", imageName)
 var img v1.Image
 var err error
@@ -141,7 +141,7 @@ func GetImage(imageName string, includeLayers bool, cacheDir string) (Image, err
 Layers: layers,
 }, errors.Wrap(err, "getting extract path for layer")
 }
-if err := GetFileSystemForLayer(layer, path, nil); err != nil {
+if err := GetFileSystemForLayer(layer, path, nil, keepOwner); err != nil {
 return Image{
 Layers: layers,
 }, errors.Wrap(err, "getting filesystem for layer")
@@ -166,7 +166,7 @@ func GetImage(imageName string, includeLayers bool, cacheDir string) (Image, err
 return Image{}, err
 }
 // extract fs into provided dir
-if err := GetFileSystemForImage(img, path, nil); err != nil {
+if err := GetFileSystemForImage(img, path, nil, keepOwner); err != nil {
 return Image{
 FSPath: path,
 Layers: layers,
@@ -241,7 +241,7 @@ func SortMap(m map[string]string) string {
 }
 
 // GetFileSystemForLayer unpacks a layer to local disk
-func GetFileSystemForLayer(layer v1.Layer, root string, whitelist []string) error {
+func GetFileSystemForLayer(layer v1.Layer, root string, whitelist []string, keepOwner bool) error {
 empty, err := DirIsEmpty(root)
 if err != nil {
 return err
@@ -254,12 +254,12 @@ func GetFileSystemForLayer(layer v1.Layer, root string, whitelist []string) erro
 if err != nil {
 return err
 }
-return unpackTar(tar.NewReader(contents), root, whitelist)
+return unpackTar(tar.NewReader(contents), root, whitelist, keepOwner)
 }
 
 // unpack image filesystem to local disk
 // if provided directory is not empty, do nothing
-func GetFileSystemForImage(image v1.Image, root string, whitelist []string) error {
+func GetFileSystemForImage(image v1.Image, root string, whitelist []string, keepOwner bool) error {
 empty, err := DirIsEmpty(root)
 if err != nil {
 return err
@@ -268,7 +268,7 @@ func GetFileSystemForImage(image v1.Image, root string, whitelist []string) erro
 logrus.Infof("using cached filesystem in %s", root)
 return nil
 }
-if err := unpackTar(tar.NewReader(mutate.Extract(image)), root, whitelist); err != nil {
+if err := unpackTar(tar.NewReader(mutate.Extract(image)), root, whitelist, keepOwner); err != nil {
 return err
 }
 return nil

pkg/util/tar_utils.go

@@ -36,7 +36,7 @@ type OriginalPerm struct {
 perm os.FileMode
 }
 
-func unpackTar(tr *tar.Reader, path string, whitelist []string) error {
+func unpackTar(tr *tar.Reader, path string, whitelist []string, keepOwner bool) error {
 originalPerms := make([]OriginalPerm, 0)
 for {
 header, err := tr.Next()
@@ -137,6 +137,13 @@ func unpackTar(tr *tar.Reader, path string, whitelist []string) error {
 hardlinks[target] = linkname
 }
 }
+
+if keepOwner {
+if err := os.Lchown(target, header.Uid, header.Gid); err != nil {
+logrus.Errorf("Error updating owner on %s", target)
+return err
+}
+}
 }
 
 for target, linkname := range hardlinks {