Re: Unionmount status?

From: Ric Wheeler
Date: Wed Apr 13 2011 - 13:27:11 EST

On 04/12/2011 05:36 PM, Michal Suchanek wrote:
On 12 April 2011 22:31, Ric Wheeler<ricwheeler@xxxxxxxxx> wrote:
On 04/12/2011 11:00 AM, Michal Suchanek wrote:

as some already know the Unionmount VFS union which has been in
development for some years now is the only True Union (TM) that can be
accepted into the kernel mainline by the VFS maintainers (for reasons
of their own which you can surely find if you search the web or ask
them directly).

The current UnionMount version that can be found here:;a=shortlog;h=refs/heads/ext2_works

works for me as good as aufs does. That is I can build a live CD using
this unioning solution and it boots and runs without any apparent

There are probably many possible uses of the union which I did not
test nor did I test long term stability of using the unioned
filesystem. As far as ephemeral live systems go it works fine for me,

The issue is that while the code is (nearly) finished it is not yet
merged into mainline and as I am not familiar with the details of
ever-changing Linux VFS layer forward-porting this code to current
kernels is somewhat challenging.

What is the plan with unionmount now?

What is required for it to be merged into mainline?


Hi Michal,

People are actively looking to see what union mount (or overlayfs) solution
to pursue. Val has shifted her focus away from kernel hacking these days,
but did refresh her patch set in the last month or so.
I am not aware of such refreshed patch set, at least it is not
published in her repo.

Val posted the refreshed patches with the title on March 22nd:


Miklos has an overlay file system that has also been posted upstream.
I have no idea about his other overlay filesystem either.

I think that testing like you did and getting more eyes to look at the code
is the next key step for both projects.

Could you provide more details?

I am not following the Linux fs development closely.



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