Merge pull request #108 from nalind/layerless-images

Stop rejecting creation of images with no layers

cmd/containers-storage/create.go

@@ -88,7 +88,11 @@ func createImage(flags *mflag.FlagSet, action string, m storage.Store, args []st
 		}
 		paramMetadata = string(b)
 	}
-	image, err := m.CreateImage(paramID, paramNames, args[0], paramMetadata, nil)
+	layer := ""
+	if len(args) > 0 {
+		layer = args[0]
+	}
+	image, err := m.CreateImage(paramID, paramNames, layer, paramMetadata, nil)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "%v\n", err)
 		return 1
@@ -168,7 +172,7 @@ func init() {
 		names:       []string{"create-image", "createimage"},
 		optionsHelp: "[options [...]] topLayerNameOrID",
 		usage:       "Create a new image using layers",
-		minArgs:     1,
+		minArgs:     0,
 		maxArgs:     1,
 		action:      createImage,
 		addFlags: func(flags *mflag.FlagSet, cmd *command) {

images.go

@@ -24,8 +24,9 @@ type Image struct {
 	// unique among images.
 	Names []string `json:"names,omitempty"`
 
-	// TopLayer is the ID of the topmost layer of the image itself.
-	// Multiple images can refer to the same top layer.
+	// TopLayer is the ID of the topmost layer of the image itself, if the
+	// image contains one or more layers.  Multiple images can refer to the
+	// same top layer.
 	TopLayer string `json:"layer"`
 
 	// Metadata is data we keep for the convenience of the caller.  It is not

store.go

@@ -775,30 +775,32 @@ func (s *store) CreateImage(id string, names []string, layer, metadata string, o
 		id = stringid.GenerateRandomID()
 	}
 
-	lstore, err := s.LayerStore()
-	if err != nil {
-		return nil, err
-	}
-	lstores, err := s.ROLayerStores()
-	if err != nil {
-		return nil, err
-	}
-	var ilayer *Layer
-	for _, store := range append([]ROLayerStore{lstore}, lstores...) {
-		store.Lock()
-		defer store.Unlock()
-		if modified, err := store.Modified(); modified || err != nil {
-			store.Load()
+	if layer != "" {
+		lstore, err := s.LayerStore()
+		if err != nil {
+			return nil, err
 		}
-		ilayer, err = store.Get(layer)
-		if err == nil {
-			break
+		lstores, err := s.ROLayerStores()
+		if err != nil {
+			return nil, err
 		}
+		var ilayer *Layer
+		for _, store := range append([]ROLayerStore{lstore}, lstores...) {
+			store.Lock()
+			defer store.Unlock()
+			if modified, err := store.Modified(); modified || err != nil {
+				store.Load()
+			}
+			ilayer, err = store.Get(layer)
+			if err == nil {
+				break
+			}
+		}
+		if ilayer == nil {
+			return nil, ErrLayerUnknown
+		}
+		layer = ilayer.ID
 	}
-	if ilayer == nil {
-		return nil, ErrLayerUnknown
-	}
-	layer = ilayer.ID
 
 	ristore, err := s.ImageStore()
 	if err != nil {