Union mount
A union mount is a mount that allows several filesystems to be mounted at one time, appearing to be one filesystem.[1]
Rather than mounting each filesystem at a different place in the directory hierarchy, a union mount overlays the filesystems, creating a unified hierarchy. Thus, any given directory (or "folder") in the resulting filesystem may contain files and subdirectories from any or all of the underlying filesystems.[2][3][4][5]
Generally one of the filesystems will be mounted read-write, while other filesystems are mounted read-only. Union mounts are implemented by union filesystems such as UnionFS and AUFS, frequently used by Live CDs. They originated with Plan 9 and its concept of union directories.[6]
If one wants to mount different filesystems distributed among a network (rather than being located on the same machine), GlusterFS offers means of doing so.[7]
References [edit]
- ^ Pendry, Jan-Simon; Marshall Kirk McKusick (December 1995). "Union Mounts in 4.4BSD-Lite". Proceedings of the USENIX Technical Conference on UNIX and Advanced Computing Systems: 25–33. Retrieved 25 November 2007.
- ^ Wright, Charles P.; Jay Dave, Puja Gupta, Harikesavan Krishnan, Erez Zadok, and Mohammad Nayyer Zubair. "Versatility and Unix Semantics in a Fan-Out Unification File System". Stony Brook University Technical Report FSL-04-01b. Retrieved 25 November 2007.
- ^ Aurora, Valerie; Henson (March 2009). "Unioning file systems: Architecture, features, and design choices". lwn.net. Retrieved 21 December 2009.
- ^ Aurora, Valerie; Henson (March 2009). "Union file systems: Implementations, part I". lwn.net. Retrieved 21 December 2009.
- ^ Aurora, Valerie; Henson (April 2009). "Unioning file systems: Implementations, part 2". lwn.net. Retrieved 21 December 2009.
- ^ Blunck, Jan (May 2009). "VFS based Union Mount (V3)". lwn.net. Retrieved 21 December 2009.
- ^ About GlusterFS. November 2009. Retrieved 4 March 2013.
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