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Developer(s) Junjiro Okajima
Full name Advanced multi layered unification filesystem
Introduced 2006
File system permissions POSIX
Supported operating systems Linux via third-party kernel module

aufs (short for advanced multi-layered unification filesystem) implements a union mount for Linux file systems. The name is an acronym which originally stood for AnotherUnionFS, but since version 2 it stands for "advanced multi-layered unification filesystem".

Developed by Junjiro Okajima in 2006,[1] aufs is a complete rewrite of the earlier UnionFS. It aimed to improve reliability and performance, but also introduced some new concepts, like writable branch balancing,[2] and other improvements – some of which are now implemented in the UnionFS 2.x branch.

aufs was rejected for merging into mainline Linux. Its code was criticized for being "dense, unreadable, and uncommented".[3] Instead, OverlayFS was merged in the Linux kernel.[4][5] After several attempts, the author has given it up.[6]


Docker originally used aufs for container filesystem layers. It is still available as one of the supported storage backends.

Several Linux distributions have chosen aufs as a replacement for UnionFS, including:

See also[edit]


  1. ^ "History of aufs". Retrieved 2015-11-08. 
  2. ^ Goals and new features of aufs in the project's homepage
  3. ^ Aurora, Valerie (2009-04-07). "Unioning file systems: Implementations, part 2". Retrieved 2015-11-08. 
  4. ^ "overlay filesystem · torvalds/linux@e9be9d5". Retrieved 12 July 2016. 
  5. ^ Hellwig, Christoph (2009-04-10). "Re: [RFC Aufs2 #5 28/29] export lookup functions". Retrieved 2015-11-08. 
  6. ^ Okajima, Junjiro (2009-04-10). "Re: [RFC Aufs2 #5 28/29] export lookup functions". Retrieved 2015-11-08. 
  7. ^ "KNOPPIX 5.1 - Live Linux Filesystem On CD". 2013-01-05. Retrieved 2015-11-08. 
  8. ^ Linux Live scripts use AUFS for better stability
  9. ^ "Gentoo Linux - Gentoo Linux - LiveDVD 11.0". 2011-03-08. Archived from the original on 2012-04-13. Retrieved 2012-04-19. 
  10. ^ "Gentoo Linux - Gentoo Linux releases 11.2 LiveDVD". 2011-08-07. Archived from the original on 2012-04-17. Retrieved 2012-04-19. 
  11. ^ "Gentoo Linux - Gentoo Linux releases 12.0 LiveDVD". 2012-01-02. Archived from the original on 2012-04-21. Retrieved 2012-04-19. 

External links[edit]