Re: [Ubuntu] AuFS read only branch as another read only branch

Michael Johnson - MJ Sun, 16 Feb 2014 03:20:07 -0800

   Hm... do you know which version of aufs you have on 12.04? Â I found this:
   [1]http://sourceforge.net/p/aufs/aufs3-standalone/ci/aufs3.2/tree/Documentat
   ion/filesystems/aufs/
   Which says:
   Currently these features are dropped temporary from aufs3.
   See design/08plan.txt in detail.
   ...
   - nested mount, i.e. aufs as readonly no-whiteout branch of another aufs
   Â  (robr)
   ...
   Looking
   atÂ [2]http://sourceforge.net/p/aufs/aufs3-standalone/ci/aufs3.2/tree/Docume
   ntation/filesystems/aufs/design/99plan.txtÂ it looks like that feature was
   probably removed from aufs2.
   So  I  think  the  end result is that currently what you are trying to
   accomplish is not supported. Â I would guess you can accomplish what you are
   trying to by using a single, non-nested aufs mount by tweaking your create
   and copyup policies, but without knowing the reasoning behind what you are
   trying to accomplish, I can't say for certain.


   On Sun, Feb 16, 2014 at 2:57 AM, Robin Monjo <[3]robinmo...@gmail.com>
   wrote:

   Thank you for tour answer.
   Iâm pretty sure that itâs possible since ubuntu 12.04. My guess is that they
   enabled the config you quoted in newer ubuntu kernel. Here is why:
   Man page for precise 12.04
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.

   Man page for earlier version (10.04)
Any filesystem can be a branch, except aufs, sysfs,  procfs  and
              unionfs.   If  you  specify  such filesystems as an aufs branch,
              aufs will return an error saying  it  is  unsupported.   If  you
              enable  CONFIG_AUFS_ROBR,  you  can  use  aufs as a non-writable
              branch of another aufs.

   However, the simplest use case doesnât work ...
   On 16 Feb 2014, at 09:17, Michael Johnson - MJ <[4]m...@revmj.com> wrote:

   FromÂ [5]http://aufs.sourceforge.net/aufs.html:
   Any filesystem can be a branch, except aufs, sysfs, procfs and unionfs. If
   you specify such filesystems as an aufs branch, aufs will return an error
   saying it is unsupported. If you enable CONFIG_AUFS_ROBR, you can use aufs
   as a non-writable branch of another aufs.
   My guess is that the documentation with the ubuntu version simply left aufs
   out  of  the docs. Â Notice that with the right compile options, newer
   versions can use aufs as a non-writable branch as you are trying to do.

   On Sat, Feb 15, 2014 at 12:22 PM, Robin Monjo <[6]robinmo...@gmail.com>
   wrote:

     Â  Â Hello,
     Â  Â My goal is to use an AuFS read only branch as another read only
     branch:
     Â  Â I've got a directory dir0, then I make :
     mount -t aufs -o br=dir2=rw:dir0=ro none dir1
     Â  Â This gives me
     - dir0
     - dir1 Â #read only dir0
     - dir2 Â #write layer of dir1
     Â  Â I now want to use dir1 this way:
     mount -t aufs -o br=dir4=rw:dir1=ro none dir3
     Â  Â To get
     - dir0
     - dir1 Â #read only dir0
     - dir2 Â #write layer of dir0
     - dir3 Â #read only dir1 (dir1 + dir2)
     - dir4 Â #write layer of dir3
     Â  Â I'm using ubuntu 12.04 and this should work according to aufs-tools
     man
     Â  Â page:
     Â  Â  Â Any filesystem can be a branch, But some are not accepted such
     like sysfs,
     Â  Â  Â procfs and unionfs. If you specify such filesystems as an aufs
     branch,
     Â  Â  Â aufs will return an error saying it is unsupported.
     Â  Â But I got this error:
     Â  Â  Â mount: wrong fs type, bad option, bad superblock on none, missing
     codepage
     Â  Â  Â or helper program, or other error (for several filesystems (e.g.
     nfs,
     Â  Â  Â cifs) you might need a /sbin/mount. helper program) In some cases
     useful
     Â  Â  Â info is found in syslog - try dmesg | tail or so
     Â  Â and dmesg gives me
     Â  Â  Â aufs test_add:231:mount[3346]: unsupported filesystem, (aufs)
     Â  Â Am I missing something here ?
     Â  Â Regards,
     Â  Â  Robin
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   --
   Michael Johnson - MJ

   --
   Michael Johnson - MJ

References

   1. 
http://sourceforge.net/p/aufs/aufs3-standalone/ci/aufs3.2/tree/Documentation/filesystems/aufs/
   2. 
http://sourceforge.net/p/aufs/aufs3-standalone/ci/aufs3.2/tree/Documentation/filesystems/aufs/design/99plan.txt
   3. mailto:robinmo...@gmail.com
   4. mailto:m...@revmj.com
   5. http://aufs.sourceforge.net/aufs.html
   6. mailto:robinmo...@gmail.com
   7. 
http://pubads.g.doubleclick.net/gampad/clk?id=124407151&iu=/4140/ostg.clktrk

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Re: [Ubuntu] AuFS read only branch as another read only branch

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