When an application tries to access a virtual directory in a virtual base directory, Autodir creates the virtual directory in it if it does not exist already and mounts the real directory on it from the real base directory. Once this is done, a timer is started. If the virtual directory is not accessed from the virtual base directory by any application for the specified period of time, this directory is removed and the corresponding real directory in the real base directory is marked for backup.
The time period to wait for expiration can be given through a command line option to Autodir.