AuFS read only branch as another read only branch

My goal is to use an AuFS read only branch as another read only branch:

I’ve got a directory dir0, then I make :

mount -t aufs -o br=dir2=rw:dir0=ro none dir1

This gives me

- dir0
- dir1  #read only dir0
- dir2  #write layer of dir1

I now want to use dir1 this way:

mount -t aufs -o br=dir4=rw:dir1=ro none dir3

To get

- dir0
- dir1  #read only dir0
- dir2  #write layer of dir0
- dir3  #read only dir1 (dir1 + dir2)
- dir4  #write layer of dir3

I’m using ubuntu 12.04 and this should work according to aufs-tools man page:

Any filesystem can be a branch, But some are not accepted such
like sysfs, procfs and unionfs. If you specify such filesystems
as an aufs branch, aufs will return an error saying it is
unsupported.

But I got this error:

mount: wrong fs type, bad option, bad superblock on none,
missing codepage or helper program, or other error
(for several filesystems (e.g. nfs, cifs) you might
need a /sbin/mount. helper program)
In some cases useful info is found in syslog – try
dmesg | tail or so

and dmesg gives me

aufs test_add:231:mount[3346]: unsupported filesystem, (aufs)

Am I missing something here ?
Regards,
Robin

Answer

Attribution
Source : Link , Question Author : rmonjo , Answer Author : rmonjo