config OVERLAY_FS tristate "Overlay filesystem support" help An overlay filesystem combines two filesystems - an 'upper' filesystem and a 'lower' filesystem. When a name exists in both filesystems, the object in the 'upper' filesystem is visible while the object in the 'lower' filesystem is either hidden or, in the case of directories, merged with the 'upper' object. For more information see Documentation/filesystems/overlayfs.txt