Aufs

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Linux filesystem

title: "Aufs" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["free-special-purpose-file-systems", "file-systems-supported-by-the-linux-kernel", "union-file-systems"] description: "Linux filesystem" topic_path: "technology/operating-systems" source: "https://en.wikipedia.org/wiki/Aufs" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Linux filesystem ::

::data[format=table title="Infobox filesystem"]

FieldValue
nameaufs
full_nameAdvanced multi layered unification filesystem
developerJunjiro Okajima
introduction_date2006
file_system_permissionsPOSIX
OSLinux via third-party kernel module
websiteaufs.sourceforge.net
::

| name = aufs | full_name = Advanced multi layered unification filesystem | developer = Junjiro Okajima | introduction_os = | introduction_date = 2006 | partition_id = | directory_struct = | file_struct = | bad_blocks_struct = | max_filename_size = | max_files_no = | max_volume_size = | max_file_size = | filename_character_set = | dates_recorded = | date_range = | date_resolution = | forks_streams = | attributes = | file_system_permissions = POSIX | compression = | encryption = | OS = Linux via third-party kernel module | website = aufs.sourceforge.net

aufs (short for advanced multi-layered unification filesystem) implements a union mount for Linux file systems. The name originally stood for AnotherUnionFS until version 2.

Developed by Junjiro Okajima in 2006, 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, 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". Instead, OverlayFS was merged in the Linux kernel. After several attempts to merge aufs into mainline kernel, the author has given up.

Use

Aufs is included in Debian "Jessie" (v8) and Ubuntu 16.04 out of the box. Debian "Stretch" (v9) does not include aufs anymore, but provides a package aufs-dkms, which auto-compiles the aufs kernel module using Dell's dkms.

Docker originally used aufs for container filesystem layers. It is still available as one of the storage backends but is deprecated in favour of the backend which uses OverlayFS.

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

References

References

  1. "History of aufs".
  2. [http://aufs.sourceforge.net/ Goals and new features of aufs in the project's homepage]
  3. (2009-04-07). "Unioning file systems: Implementations, part 2".
  4. "overlay filesystem · torvalds/linux@e9be9d5".
  5. (2009-04-10). "Re: [RFC Aufs2 #5 28/29] export lookup functions".
  6. (2009-04-10). "Re: [RFC Aufs2 #5 28/29] export lookup functions".
  7. "Deprecated Engine Features".
  8. (2013-01-05). "KNOPPIX 5.1 - Live Linux Filesystem On CD". knopper.net.
  9. [http://www.linux-live.org/?changes Linux Live scripts] {{Webarchive. link. (2009-03-22 use AUFS for better stability)
  10. (2011-03-08). "Gentoo Linux - Gentoo Linux - LiveDVD 11.0". Gentoo.org.
  11. (2011-08-07). "Gentoo Linux - Gentoo Linux releases 11.2 LiveDVD". Gentoo.org.
  12. (2012-01-02). "Gentoo Linux - Gentoo Linux releases 12.0 LiveDVD". Gentoo.org.
  13. (2020-01-19). "Manjaro linux54 kernel PKGBUILD".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::

free-special-purpose-file-systemsfile-systems-supported-by-the-linux-kernelunion-file-systems