example_config.xml

<?xml version="1.0" encoding="utf-8"?>
<aufsconfig>
  <!-- Declare the union characteristics here -->
  <volume policy="Default">
    <!-- The drive letter of the union -->
    <letter>Q</letter>
    <!-- The volume label (display name) of the union -->
    <label>BigDrive</label>
  </volume>
  <!-- Declare all members drives of the union here -->
  <members>
    <!-- The "path attribute is required. The readonly attribute is optional; the default value is "true". If set to true, then no modifications will be done to the member's directories/files -->
    <member path="E:\" readonly="false"/>
    <member path="D:\"/>
  </members>
</aufsconfig>