Editing UnionFS (section)

==Other implementations==
Unionfs for Linux has two versions. Version 1.x is a standalone one that can be built as a module. Version 2.x is a newer, redesigned, and reimplemented one.

[[aufs]] is an alternative version of unionfs.<ref>{{cite web
| url=http://aufs.sourceforge.net
| title=aufs Homepage
| date=2017-07-02
| access-date=2017-07-17}}</ref>

[[overlayfs]] written by Miklos Szeredi has been used in OpenWRT and considered by Ubuntu and has been merged into the mainline Linux kernel on 26 October 2014<ref>{{cite web
| url=https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d1e14f1d63eb15ebe97d1a8544ddc143486b0204
| title=overlayfs merge + leak fix for d_splice_alias() failure exits
| date=2014-10-26
| first=Linus
| last=Torvalds
| access-date=2017-07-17}}</ref> after many years of development and discussion<ref>{{cite web
| url=https://lwn.net/Articles/447650/
| title=Debating overlayfs
| first=Jonathan
| last=Corbet
| date=2011-06-15
| access-date=2017-07-17}}</ref> for version 3.18 of the kernel.

''unionfs-fuse'' is an independent project, implemented as a [[Filesystem in Userspace|user space filesystem]] program, instead of a kernel module or patch. Like Unionfs, it supports copy-on-write and read-only or read–write branches.<ref>{{cite web
| url=https://github.com/rpodgorny/unionfs-fuse/blob/master/man/unionfs.8
| title=unionfs-fuse – A userspace unionfs implementation
| first=Radek
| last=Podgorny
| website=[[GitHub]]
| date=2016-11-21
| access-date=2017-07-17}}</ref>

The [[Plan 9 from Bell Labs]] operating system uses [[union mount]]s extensively to build custom [[namespace]]s per user or processes.

Union mounts have also been available in [[Berkeley Software Distribution|BSD]] since at least 1995.<ref>{{cite web
| url=https://www.usenix.org/legacy/publications/library/proceedings/neworl/mckusick.html
| title=Union Mounts in 4.4BSD-Lite
| first1=Jan-Simon
| last1=Pendry
| first2=Marshall Kirk
| last2=McKusick
| date=January 1995
| work=USENIX 1995 Technical Conference Proceedings
| access-date=2017-07-17}}</ref>

The [[GNU Hurd]] has an implementation of Unionfs.<ref>{{cite web
| url=https://www.gnu.org/software/hurd/hurd/translator/unionfs.html
| title=unionfs
| first=Thomas
| last=Schwinge
| date=2014-02-26
| work=[[GNU Hurd]]
| access-date=2017-07-17}}</ref> As of January 2008, it works, but results in a read-only mount-point.

[[mhddfs]] works like Unionfs but permits balancing files over drives with the most free space available. It is implemented as a user space filesystem.

[[mergerfs]] is a FUSE based union filesystem which offers multiple policies for accessing and writing files as well as other advanced features (xattrs, managing mixed RO and RW drives, link CoW, etc.).<ref>{{Cite web|url=https://github.com/trapexit/mergerfs|title=trapexit/mergerfs|website=GitHub|language=en|access-date=2018-10-21}}</ref>

[[Sun Microsystems]] introduced the first implementation of a stacked, layered file system with copy-on-write, whiteouts (hiding files in lower layers from higher layers), etc. as the [[Translucent File Service]] in [[SunOS]] 3, circa 1986.<ref>{{cite book
  | title = Sun/Release 3.0
  | publisher = Interleaf Technical Publishing
  | year = 1988
  | volume = 1
  | pages = 15‑1–18, 16‑1–19
  }}</ref>

[[JailbreakMe]] 3.0, a tool for [[iOS jailbreaking|jailbreaking]] iOS devices released in July 2011, uses unionfs techniques to speed up the installation process of the operating system modification.<ref>{{cite web
| url=http://www.redmondpie.com/comex-working-on-faster-jailbreaking-process-for-jailbreakme-3.0-ipad-2-jailbreak-coming-soon/
| title=Comex Working on Faster Jailbreaking Process for JailbreakMe 3.0; iPad 2 Jailbreak Coming Soon!
| first=Awais
| last=Imran
| date=2011-06-19
| publisher=Redmond Pie
| access-date=2017-07-17}}</ref>