diff --git a/core/Makefile b/core/Makefile
index 49eab0b..49abfe9 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -521,6 +521,7 @@
 # Targets for user images
 # #################################################################
 
+INTERNAL_USERIMAGES_EXT_VARIANT :=
 ifeq ($(TARGET_USERIMAGES_USE_EXT2),true)
 INTERNAL_USERIMAGES_USE_EXT := true
 INTERNAL_USERIMAGES_EXT_VARIANT := ext2
@@ -537,15 +538,18 @@
 endif
 
 ifeq ($(INTERNAL_USERIMAGES_USE_EXT),true)
+INTERNAL_USERIMAGES_DEPS := $(MKEXT2USERIMG) $(MKEXT2IMG) $(TUNE2FS) $(E2FSCK)
+INTERNAL_USERIMAGES_BINARY_PATHS := $(sort $(dir $(INTERNAL_USERIMAGES_DEPS)))
+
 # $(1): src directory
 # $(2): output file
 # $(3): label (if any)
 # $(4): ext variant (ext2, ext3, ext4)
 define build-userimage-ext-target
   @mkdir -p $(dir $(2))
-  $(hide) $(MKEXT2USERIMG) $(MKEXT2IMG) $(TUNE2FS) $(E2FSCK) $(1) $(2) $(4) $(3)
+  $(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$(PATH) \
+	  $(MKEXT2USERIMG) $(1) $(2) $(4) $(3)
 endef
-INTERNAL_USERIMAGES_DEPS := $(MKEXT2USERIMG) $(MKEXT2IMG) $(TUNE2FS) $(E2FSCK)
 else
 INTERNAL_USERIMAGES_DEPS := $(MKYAFFS2)
 endif
@@ -836,7 +840,12 @@
 	  $(HOST_OUT_EXECUTABLES)/bsdiff \
 	  $(HOST_OUT_EXECUTABLES)/imgdiff \
 	  $(HOST_OUT_JAVA_LIBRARIES)/dumpkey.jar \
-	  $(HOST_OUT_JAVA_LIBRARIES)/signapk.jar
+	  $(HOST_OUT_JAVA_LIBRARIES)/signapk.jar \
+	  $(HOST_OUT_EXECUTABLES)/mkuserimg.sh \
+	  $(HOST_OUT_EXECUTABLES)/genext2fs \
+	  $(HOST_OUT_EXECUTABLES)/tune2fs \
+	  $(HOST_OUT_EXECUTABLES)/e2fsck
+
 
 # -----------------------------------------------------------------
 # A zip of the directories that map to the target filesystem.
@@ -1135,6 +1144,7 @@
 	$(hide) ./build/tools/releasetools/img_from_target_files \
 	   -s $(extensions) \
 	   -p $(HOST_OUT) \
+	   $(addprefix --fs_type ,$(INTERNAL_USERIMAGES_EXT_VARIANT)) \
 	   $(BUILT_TARGET_FILES_PACKAGE) $@
 
 .PHONY: updatepackage
diff --git a/tools/releasetools/img_from_target_files b/tools/releasetools/img_from_target_files
index d157dca..f83188e 100755
--- a/tools/releasetools/img_from_target_files
+++ b/tools/releasetools/img_from_target_files
@@ -23,6 +23,11 @@
   -b  (--board_config)  <file>
       Deprecated.
 
+  -f  (--fs_type) <value>
+      The file system type of the user image files to be created.
+      It can be ext fs variants, such as ext2, ext3, ext4, etc.
+      Default is yaffs.
+
 """
 
 import sys
@@ -47,6 +52,10 @@
 
 OPTIONS = common.OPTIONS
 
+class UserImageOptions(object): pass
+USERIMAGE_OPTIONS = UserImageOptions()
+USERIMAGE_OPTIONS.fs_type = None
+
 
 def AddUserdata(output_zip):
   """Create an empty userdata image and store it in output_zip."""
@@ -61,9 +70,17 @@
   os.mkdir(user_dir)
   img = tempfile.NamedTemporaryFile()
 
-  p = common.Run(["mkyaffs2image", "-f", user_dir, img.name])
+  build_command = []
+  if USERIMAGE_OPTIONS.fs_type is not None and USERIMAGE_OPTIONS.fs_type.startswith("ext"):
+    build_command = ["mkuserimg.sh",
+                     user_dir, img.name, USERIMAGE_OPTIONS.fs_type, "userdata"]
+  else:
+    build_command = ["mkyaffs2image", "-f",
+                     user_dir, img.name]
+
+  p = common.Run(build_command);
   p.communicate()
-  assert p.returncode == 0, "mkyaffs2image of userdata.img image failed"
+  assert p.returncode == 0, "build userdata.img image failed"
 
   common.CheckSize(img.name, "userdata.img")
   output_zip.write(img.name, "userdata.img")
@@ -94,10 +111,18 @@
     if (e.errno == errno.EEXIST):
       pass
 
-  p = common.Run(["mkyaffs2image", "-f",
-                  os.path.join(OPTIONS.input_tmp, "system"), img.name])
+  build_command = []
+  if USERIMAGE_OPTIONS.fs_type is not None and USERIMAGE_OPTIONS.fs_type.startswith("ext"):
+    build_command = ["mkuserimg.sh",
+                     os.path.join(OPTIONS.input_tmp, "system"), img.name,
+                     USERIMAGE_OPTIONS.fs_type, "system"]
+  else:
+    build_command = ["mkyaffs2image", "-f",
+                     os.path.join(OPTIONS.input_tmp, "system"), img.name]
+
+  p = common.Run(build_command)
   p.communicate()
-  assert p.returncode == 0, "mkyaffs2image of system.img image failed"
+  assert p.returncode == 0, "build system.img image failed"
 
   img.seek(os.SEEK_SET, 0)
   data = img.read()
@@ -118,13 +143,15 @@
   def option_handler(o, a):
     if o in ("-b", "--board_config"):
       pass       # deprecated
+    elif o in ("-f", "--fs_type"):
+      USERIMAGE_OPTIONS.fs_type = a
     else:
       return False
     return True
 
   args = common.ParseOptions(argv, __doc__,
-                             extra_opts="b:",
-                             extra_long_opts=["board_config="],
+                             extra_opts="b:f:",
+                             extra_long_opts=["board_config=", "fs_type="],
                              extra_option_handler=option_handler)
 
   if len(args) != 2: