Scripts in this directory helps you working on private overlay more easily.


aufs is a kind of unionfs, which allows you to union (or merge) multiple directories as one directory. For Chromium OS Factory Software Platform, we need to union files in factory repo (chromiumos/platform/factory) with files in board overlay. When we are developing codes in board overlay, files in factory repo still stay in factory repo. This makes development a little harder, for example, you need to go back to factory repo to read the definition of an utility function. Or you need to figure out how to setup your auto-complete plugin such that both files in factory repo and board overlay can be found.

With aufs, we create a working directory (workspace) for you, that both files from factory repo and board overlay exists in this directory. There are also some utilities help you manage your modifications.

File System Structure

The workspace is the union of three directories:

  • temp directory (readwrite)
  • board overlay (readonly)
  • factory repo (readonly)

When you access a file, aufs first look into temp directory, then board overlay, and finally factory repo. Since board overlay and factory repo are both readonly, when you modify a file, the file is copied to temp directory, and your modification is saved in that copy. On the other hand, if you want to delete a file, a whiteout marker is created in temp directory with the file name: .wh.<deleted-filename>. For example, if you deleted py/, py/ will be created under temp directory.



Usage: [WORKING_DIR=...] [BOARD=...] [OVERLAY_DIR=...]

This will create a temp directory under /tmp and mount the aufs under ~/workspace.

  • WORKING_DIR: specify the working directory (default: ~/workspace)
  • OVERLAY_DIR: specify the board overlay directory, for example: ~/trunk/src/privte-overlays/overlay-samus-private/chromeos-base/chromeos-factory-board/files. If OVERLAY_DIR is not specified, BOARD will be used to determine the board overlay directory.
  • BOARD: specify the board name to find OVERLAY_DIR.


Usage: [WORKING_DIR=...]

Sample output

Modified files:
MF Makefile
A  new_file
DO py/test/test_lists/
  • M: this file is modified

  • A: this file is a new file

  • D: this file is deleted

  • F: this file belongs to factory repo

  • O: this file belongs to board overlay


Usage: [WORKING_DIR=...] [file1 file2 ...]

Similar to git diff command, this command shows changes that haven't been sync to factory repo or board overlay. By providing a list of files to restrict the script only showing changes of those files.

devtools/aufs/ [-i|--interactive]

Usage: [WORKING_DIR=...] [file1 file2 ...]

Sync changed files to factory repo and board overlay. Changes of existing files (delete / modify) will be applied to files on factory repo or board overlay. For new files, they will be moved to board overlay. If interactive is set, a question will be prompt for each files let you decide which directory this file should go to.

By providing a list of files, the script is restricted only syncing those files.


Usage: [WORKING_DIR=...] [file1 file2 ...]

Discard unstaged changes. By providing a list of files, the script is restricted only reverting those files.


Usage: [WORKING_DIR=...]

Try to unmount working directory and clean up temp directory. If there are unstaged files, this script will abort, working directory will not be unmounted.