prevent deletion if image is used by a running container

server.go

@@ -1257,6 +1257,26 @@ func (srv *Server) ImageDelete(name string, autoPrune bool) ([]APIRmi, error) {
 		}
 		return nil, nil
 	}
+
+	// Prevent deletion if image is used by a running container
+	for _, container := range srv.runtime.List() {
+		if container.State.Running {
+			parent, err := srv.runtime.repositories.LookupImage(container.Image)
+			if err != nil {
+				return nil, err
+			}
+
+			if err := parent.WalkHistory(func(p *Image) error {
+				if img.ID == p.ID {
+					return fmt.Errorf("Conflict, cannot delete %s because the running container %s is using it", name, container.ID)
+				}
+				return nil
+			}); err != nil {
+				return nil, err
+			}
+		}
+	}
+
 	if strings.Contains(img.ID, name) {
 		//delete via ID
 		return srv.deleteImage(img, "", "")