Unix File System

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The Unix File System ( UFS ) is a file system whose development began in 1980 by Bill Joy under the name UFS, based loosely on the data structures of the Unix Version 6 file system. Two years later, after the file system was already in use at some universities, Marshall Kirk McKusick came to the project and mainly devoted himself to improved allocation mechanisms. This is when the name Fast File System appears for the first time . With UNIX System V Version 4, UFS was also adopted in the AT&T version of UNIX and replaced the file system from UNIX Version 6 as the default file system.


Berkeley Fast File System (FFS)

The UFS is currently used in the Berkeley Fast File System variant by various BSD derivatives such as FreeBSD , NetBSD and OpenBSD as well as in Solaris and NeXTStep . It is also available on Linux and Mac OS X (at least up to version 10.4 ), but it is not part of the standard. In terms of design, the ext2 file system created in the Linux project is a descendant of UFS.

As of version 7, Solaris offers an option that implements journaling in UFS (prior to Solaris 7, journaling could be activated via Trans-Devices of the Solstice DiskSuite ). Among the BSD operating systems there is the Softupdates extension, an efficient method of writing the metadata that keeps the file system in a consistent state at all times . Furthermore, NetBSD has supported metadata journaling since mid-2008. NetBSD 5.0 ​​was the first stable version with support for metadata journaling, but where it was still listed as a preview .


UFS2 is an extension of UFS and was introduced in FreeBSD 5.x. UFS2 mainly brings the following changes:

  • Support for file systems larger than 1  TiB .
  • It is possible to create snapshots in the file system .
  • The “file system check” after a system crash takes place in the background. This greatly reduces the time it takes to boot on large file systems.
  • Additional file attributes have been added, including a POSIX- compliant implementation of access control lists.

See also


Web links

Individual evidence

  1. ^ A Fast File System for UNIX - University of Wisconsin – Madison , October 30, 2008
  2. Mac OS X 10.5 Leopard: Installing on a UFS-formatted volume. Apple, June 12, 2012, accessed on March 28, 2020 : “You cannot install Mac OS X Leopard on a UFS-formatted volume. In addition, you cannot upgrade older versions of Mac OS X installed on UFS-formatted volumes to Leopard. To upgrade to Leopard you need to reformat your startup volume. "
  3. ^ Metadata journaling support added to FFS. In: NetBSD: Recent Changes and News. NetBSD, July 31, 2008, accessed April 9, 2018 .