Debian also has aufs [LWN.net]

Debian also has aufs

Posted Oct 17, 2013 16:16 UTC (Thu) by dpquigl (guest, #52852)
In reply to: Debian also has aufs by juliank
Parent article: Deploying Docker

I also don't agree with Ubuntu's assessment that it will never be merged upstream. I agree that AUFS is complex. Even though AUFS is a complete rewrite at this point of our original UnionFS implementation it suffers from the same problems that all stackable file systems do. That the kernel is not really made to support file system stacking and as such there are a lot of issues with data structures potentially changing from underneath us. Even with this concern I found a mailing list post on LKML where Al Viro said he was open to looking at these implementations again for inclusion. In the past he had said no way no how for implementations like AUFS but with that latest statement there might be hope to get it upstreamed.

Stackable file systems in general are a bit complex since you're rebuilding part of the VFS and are essentially building in support for the equivalent of a windows filter driver at the file system level. That complexity shouldn't preclude it from inclusion though as long as its clean and properly documented (which we have documentation for stackable file systems in the Documentation folder).

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Debian also has aufs

Posted Oct 17, 2013 17:01 UTC (Thu) by alexl (guest, #19068) [Link] (1 responses)

The one viro is looking on for possible inclusion is overlayfs, not aufs.

Debian also has aufs

Posted Oct 17, 2013 20:45 UTC (Thu) by dpquigl (guest, #52852) [Link]

Based on the email I read it seems like he would give consideration to any union namespace implementation. I would like to see a feature comparison though. Last I checked Unionfs/AUFS/overlayfs/unionmounts did not all provide the same functionality and I think that some of the features of AUFS might be needed for Docker.

"I *have* looked at unionmount lately, and the recent modifications dhowells
is doing there are closing most of my problems with that; on the other hand,
there's no fundamental reason why both can't get merged. Hell, might as
well resurrect aufs, while we are at it..." - Al Viro

https://lkml.org/lkml/2013/3/12/637

Debian also has aufs

Posted Oct 17, 2013 18:22 UTC (Thu) by juliank (guest, #45896) [Link]

IIRC, he made a joke about including aufs.

Debian also has aufs

Posted Oct 17, 2013 21:09 UTC (Thu) by dpquigl (guest, #52852) [Link]

Also a minor nit for the article. It says the only differences between files are saved. This is not correct. Only the modified files are saved would be more correct. AUFS OverlayFS and unionmounts are namespace unification file systems. They just unify the name space not the data in the files itself. So a 1 byte change to a 400 meg file will cause the 400 meg file to be copied up to the r/w branch.