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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Unix File System</span></span>

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</style><div role="note" class="hatnote navigation-not-searchable">This article is about the file system implementation in some Unix and BSD operating systems. For general Unix file system principles, see <a href="Unix_filesystem" title="Unix filesystem">Unix filesystem</a>.</div>

<div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="Universal_Flash_Storage" title="Universal Flash Storage">Universal Flash Storage</a>, a storage device standard with the same abbreviation.</div>

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</style><table class="infobox vevent"><caption class="infobox-title summary">UFS</caption><tbody><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="Software_developer" class="mw-redirect" title="Software developer">Developer(s)</a></th><td class="infobox-data"><a href="Computer_Systems_Research_Group" title="Computer Systems Research Group">CSRG</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Full name</th><td class="infobox-data">UNIX file system</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Introduced</th><td class="infobox-data">with <a href="BSD" class="mw-redirect" title="BSD">4.2BSD</a></td></tr><tr><th colspan="2" class="infobox-header">Structures</th></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Directory contents</th><td class="infobox-data">tables</td></tr><tr><th colspan="2" class="infobox-header">Limits</th></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Max volume size</th><td class="infobox-data">2<sup>73</sup> bytes (8 <a href="Zebibyte" class="mw-redirect" title="Zebibyte">ZiB</a>)</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Max file size</th><td class="infobox-data">2<sup>73</sup> bytes (8 <a href="Zebibyte" class="mw-redirect" title="Zebibyte">ZiB</a>)</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Max filename length</th><td class="infobox-data">255 bytes</td></tr><tr><th colspan="2" class="infobox-header">Features</th></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Dates recorded</th><td class="infobox-data">UFS1 and UFS2: last access time (atime), last modified time (mtime), last inode change time (ctime), UFS2: inode creation time (birthtime)<sup id="cite_ref-dinode_1-0" class="reference"><a href="#cite_note-dinode-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Date range</th><td class="infobox-data">UFS1: December 14, 1901–January 18, 2038, UFS2: 64-bit signed integer offset from <a href="Unix_time" title="Unix time">epoch</a><sup id="cite_ref-dinode_1-1" class="reference"><a href="#cite_note-dinode-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Date resolution</th><td class="infobox-data">UFS1 and UFS2: Nanosecond<sup id="cite_ref-dinode_1-2" class="reference"><a href="#cite_note-dinode-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th colspan="2" class="infobox-header">Other</th></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Supported<br><a href="Operating_system" title="Operating system">operating systems</a></th><td class="infobox-data"><a href="A/UX" title="A/UX">A/UX</a>, <a href="DragonFly_BSD" title="DragonFly BSD">DragonFly BSD</a>, <a href="FreeBSD" title="FreeBSD">FreeBSD</a>, <a href="FreeNAS" class="mw-redirect" title="FreeNAS">FreeNAS</a>, <a href="NAS4Free" class="mw-redirect" title="NAS4Free">NAS4Free</a>, <a href="HP-UX" title="HP-UX">HP-UX</a>, <a href="NetBSD" title="NetBSD">NetBSD</a>, <a href="NeXTSTEP" title="NeXTSTEP">NeXTSTEP</a>, <a href="Linux" title="Linux">Linux</a>, <a href="OpenBSD" title="OpenBSD">OpenBSD</a>, <a href="Illumos" title="Illumos">illumos</a>, <a href="Solaris_(operating_system)" class="mw-redirect" title="Solaris (operating system)">Solaris</a>, <a href="SunOS" title="SunOS">SunOS</a>, <a href="Tru64_UNIX" title="Tru64 UNIX">Tru64 UNIX</a>, <a href="UNIX_System_V" title="UNIX System V">UNIX System V</a>, <a href="Orbis_OS" class="mw-redirect" title="Orbis OS">Orbis OS</a>, and others</td></tr></tbody></table>

<p>The <b>Unix file system</b> (<b>UFS</b>) is a family of <a href="File_system" title="File system">file systems</a> supported by many <a href="Unix" title="Unix">Unix</a> and <a href="Unix-like" title="Unix-like">Unix-like</a> operating systems. It is a distant descendant of the original filesystem used by <a href="Version_7_Unix" title="Version 7 Unix">Version 7 Unix</a>.

</p>

<div class="mw-heading mw-heading2"><h2 id="Design">Design</h2></div>

<p>A UFS volume is composed of the following parts:

</p>

<ul><li>A few blocks at the beginning of the partition reserved for <a href="Bootstrapping_(computing)" class="mw-redirect" title="Bootstrapping (computing)">boot blocks</a> (which must be initialized separately from the filesystem)</li>

<li>A superblock, containing a <a href="Magic_number_(programming)" title="Magic number (programming)">magic number</a> identifying this as a UFS filesystem, and some other vital numbers describing this filesystem's geometry and statistics and behavioral tuning parameters</li>

<li>A collection of cylinder groups. Each cylinder group has the following components:

<ul><li>A backup copy of the superblock</li>

<li>A cylinder group header, with statistics, free lists, etc., about this cylinder group, similar to those in the superblock</li>

<li>A number of <a href="Inode" title="Inode">inodes</a>, each containing file attributes</li>

<li>A number of <a href="Block_(data_storage)" title="Block (data storage)">data blocks</a></li></ul></li></ul>

<p>Inodes are numbered sequentially, starting at 0. Inode 0 is reserved for unallocated directory entries, inode 1 was the inode of the bad block file in historical UNIX versions, followed by the inode for the <a href="Root_directory" title="Root directory">root directory</a>, which is always inode 2 and the inode for the lost+found directory which is inode 3.

</p><p>Directory files contain only the list of filenames in the directory and the inode associated with each file. All file <a href="Metadata_(computing)" class="mw-redirect" title="Metadata (computing)">metadata</a> is kept in the inode.

</p>

<div class="mw-heading mw-heading2"><h2 id="History_and_evolution">History and evolution</h2></div>

<p>Early Unix filesystems were referred to simply as <i>FS</i>. FS only included the boot block, superblock, a clump of <a href="Inode" title="Inode">inodes</a>, and the data blocks. This worked well for the small disks early Unixes were designed for, but as technology advanced and disks grew larger, moving the head back and forth between the clump of inodes and the data blocks they referred to caused <a href="Hard_disk_drive_performance_characteristics#Seek_time" title="Hard disk drive performance characteristics">thrashing</a>. <a href="Kirk_McKusick" class="mw-redirect" title="Kirk McKusick">Marshall Kirk McKusick</a>, then a <a href="University_of_California%2C_Berkeley" title="University of California, Berkeley">Berkeley</a> graduate student, optimized the V7 FS layout to create <a href="4.2BSD" class="mw-redirect" title="4.2BSD">BSD 4.2</a>'s FFS (Fast File System) by inventing cylinder groups, which break the disk up into smaller chunks, with each group having its own inodes and data blocks.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>

</p><p>The intent of BSD FFS is to try to localize associated data blocks and metadata in the same cylinder group and, ideally, all of the contents of a directory (both data and metadata for all the files) in the same or nearby cylinder group, thus reducing <a href="File_system_fragmentation" title="File system fragmentation">fragmentation</a> caused by scattering a directory's contents over a whole disk.

</p><p>Some of the performance parameters in the superblock included number of tracks and sectors, disk rotation speed, head speed, and alignment of the sectors between tracks. In a fully optimized system, the head could be moved between close tracks to read scattered sectors from alternating tracks while waiting for the platter to spin around.

</p><p>As disks grew larger and larger, sector-level optimization became obsolete (especially with disks that used linear sector numbering and variable sectors per track). With larger disks and larger files, fragmented reads became more of a problem. To combat this, BSD originally increased the filesystem block size from one sector to 1 K in 4.0 BSD; and, in FFS, increased the filesystem block size from 1 K to 8 K. This has several effects. The chance of a file's sectors being contiguous is much greater. The amount of overhead to list the file's blocks is reduced, while the number of bytes representable by any given number of blocks is increased.

</p><p>Larger disk sizes are also possible, since the maximum number of blocks is limited by a fixed bit-width block number. However, with larger block sizes, disks with many small files will waste space, since each file must occupy at least one block. Because of this, BSD added <i>block-level fragmentation</i>, also called <a href="Block_suballocation" title="Block suballocation">block suballocation, tail merging, or tail packing</a>, where the last partial block of data from several files may be stored in a single "fragment" block instead of multiple mostly empty blocks.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

</p><p>The work on Berkeley FFS was widely adopted by other Unix vendors, and the family of filesystems derived from it are collectively known as UFS.

</p>

<div class="mw-heading mw-heading2"><h2 id="Implementations">Implementations</h2></div>

<p>Vendors of some proprietary Unix systems, such as <a href="SunOS" title="SunOS">SunOS</a> / <a href="Solaris_(operating_system)" class="mw-redirect" title="Solaris (operating system)">Solaris</a>, <a href="System_V_Release_4" class="mw-redirect" title="System V Release 4">System V Release 4</a>, <a href="HP-UX" title="HP-UX">HP-UX</a>, and <a href="Tru64_UNIX" title="Tru64 UNIX">Tru64 UNIX</a>, and open Unix derived systems like <a href="Illumos" title="Illumos">illumos</a>, have adopted UFS. Most of them adapted UFS to their own uses, adding proprietary extensions that may not be recognized by other vendors' versions of Unix. Many have continued to use the original block size and data field widths as the original UFS, so some degree of read compatibility remains across platforms. Compatibility between implementations as a whole is spotty at best.

</p><p>As of <a href="Solaris_7" class="mw-redirect" title="Solaris 7">Solaris 7</a>, <a href="Sun_Microsystems" title="Sun Microsystems">Sun Microsystems</a> included UFS Logging, which brought <a href="Journaling_file_system" title="Journaling file system">filesystem journaling</a> to UFS, which is still available in current versions of Solaris and illumos.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> Solaris UFS also has extensions for large files and large disks and other features.

</p><p>In 4.4BSD and <a href="Berkeley_Software_Distribution" title="Berkeley Software Distribution">BSD</a> Unix systems derived from it, such as <a href="FreeBSD" title="FreeBSD">FreeBSD</a>, <a href="NetBSD" title="NetBSD">NetBSD</a>, <a href="OpenBSD" title="OpenBSD">OpenBSD</a>, and <a href="DragonFly_BSD" title="DragonFly BSD">DragonFly BSD</a>, the implementation of UFS1 and UFS2 is split into two layers: an upper layer that provides the directory structure and supports metadata (permissions, ownership, etc.) in the inode structure, and lower layers that provide data containers implemented as inodes. This was done to support both the traditional FFS and the <a href="Log-structured_File_System_(BSD)" title="Log-structured File System (BSD)">LFS</a> log-structured file system with shared code for common functions. The upper layer is called "UFS", and the lower layers are called "FFS" and "LFS". In some of those systems, the term "FFS" is used for the combination of the FFS lower layer and the UFS upper layer, and the term "LFS" is used for the combination of the LFS lower layer and the UFS upper layer.

</p><p>Kirk McKusick implemented block reallocation, a technique that reorders the blocks in the file system just before the writes are done to reduce fragmentation and control file system aging. He also implemented <a href="Soft_updates" title="Soft updates">soft updates</a>, a mechanism that maintains the file system consistency without limiting the performance in the way the traditional sync mode did. This has the side effect of reducing the requirement of file system checking after a crash or power failure. To overcome the remaining issues after a failure, a background fsck utility was introduced.

</p><p>In UFS2, Kirk McKusick and <a href="Poul-Henning_Kamp" title="Poul-Henning Kamp">Poul-Henning Kamp</a> extended the FreeBSD FFS and UFS layers to add 64-bit block pointers (allowing volumes to grow up to 8 <a href="Zebibyte" class="mw-redirect" title="Zebibyte">zebibytes</a>), variable-sized blocks (similar to <a href="Extent_(file_systems)" title="Extent (file systems)">extents</a>), extended flag fields, additional 'birthtime' stamps, extended attribute support and POSIX1.e ACLs. UFS2 became the supported UFS version starting with FreeBSD 5.0. FreeBSD also introduced soft updates and the ability to make file system <a href="Snapshot_(computer_storage)" title="Snapshot (computer storage)">snapshots</a> for both UFS1 and UFS2. These have since been ported to NetBSD, but eventually soft updates (called soft dependencies in NetBSD) was removed from NetBSD 6.0 in favor of the less complex file system journaling mechanism called <a href="WAPBL" class="mw-redirect" title="WAPBL">WAPBL</a> (also referred as logging), which was added to FFS in NetBSD 5.0. OpenBSD supported soft updates from version 2.9<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> until support was dropped in version 7.4,<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> and it has had UFS2 (FFS2) support (no ACLs) since version 4.2.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> OpenBSD has now made UFS2 the default UFS version and will be included with the 6.7 release.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Since FreeBSD 7.0, UFS also supports <a href="Journaling_file_system" title="Journaling file system">filesystem journaling</a> using the gjournal <a href="GEOM" title="GEOM">GEOM</a> provider. FreeBSD 9.0 adds support for lightweight journaling on top of soft updates (SU+J), which greatly reduces the need for background fsck, and NFSv4 ACLs.

</p><p>FreeBSD, NetBSD, OpenBSD, and DragonFly BSD also include the <a href="Dirhash" title="Dirhash">Dirhash</a> system, developed by Ian Dowse. This system maintains an in-memory hash table to speed up directory lookups. Dirhash alleviates a number of performance problems associated with large directories in UFS.

</p><p><a href="Linux" title="Linux">Linux</a> includes a UFS implementation for binary compatibility at the read level with other Unixes, but since there is no standard implementation for the vendor extensions to UFS, Linux does not have full support for writing to UFS. The native Linux <a href="Ext2" title="Ext2">ext2</a> filesystem was inspired by UFS1 but does not support fragments and there are no plans to implement soft updates. (In some 4.4BSD-derived systems, the UFS layer can use an ext2 layer as a container layer, just as it can use FFS and LFS.)

</p><p><a href="NeXTStep" class="mw-redirect" title="NeXTStep">NeXTStep</a>, which was BSD-derived, also used a version of UFS. In <a href="Apple_Inc." title="Apple Inc.">Apple</a>'s <a href="MacOS" title="MacOS">Mac OS X</a>, it was available as an alternative to <a href="HFS_Plus" title="HFS Plus">HFS+</a>, their proprietary filesystem. However, as of <a href="Mac_OS_X_Leopard" title="Mac OS X Leopard">Mac OS X Leopard</a>, it was no longer possible to install Mac OS X on a UFS-formatted volume. In addition, one cannot upgrade older versions of Mac OS X installed on UFS-formatted volumes to Leopard; upgrading requires reformatting the startup volume.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> There was a 4 GB file limit for disks formatted as UFS in Mac OS X. As of <a href="Mac_OS_X_Lion" class="mw-redirect" title="Mac OS X Lion">Mac OS X Lion</a>, UFS support was completely dropped.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup>

</p>

<ul><li><a href="Comparison_of_file_systems" title="Comparison of file systems">Comparison of file systems</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

<div class="mw-heading mw-heading3"><h3 id="Citations">Citations</h3></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://svnweb.freebsd.org/base/head/sys/ufs/ufs/dinode.h?revision=313780&view=markup">"[base] Contents of /Head/Sys/Ufs/Ufs/Dinode.h"</a>.</cite></span>

</li>

<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.oreilly.com/openbook/opensources/book/kirkmck.html">"Open Sources: Voices from the Open Source Revolution"</a>. 29 March 1999.</cite></span>

</li>

<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><cite id="CITEREFMcKusickJoyLefflerFabry1984" class="citation journal cs1">McKusick, K M; Joy, W; Leffler, S; Fabry, R (August 1984). <a rel="nofollow" class="external text" href="https://www.cs.cornell.edu/Courses/cs614/2003SP/papers/KJL84.pdf">"A Fast File System for UNIX"</a> <span class="cs1-format">(PDF)</span>. <i>ACM Transactions on Computer Systems</i>. <b>2</b> (3): <span class="nowrap">181–</span>197. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F989.990">10.1145/989.990</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:222285164">222285164</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></span>

</li>

<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite id="CITEREFAllen2005" class="citation web cs1">Allen, Hervey (2005-06-20). <a rel="nofollow" class="external text" href="http://ws.edu.isoc.org/workshops/2005/ccTLD-Nairobi/day1/freebsd/intro-freebsd-additional-topics-1up.pdf">"UFS2 and Soft Updates make for a powerful combination"</a> <span class="cs1-format">(PDF)</span>. <i>Introduction to FreeBSD, PacNOG I Workshop, Additional Topics</i>. Network Startup Resource Center. p. 23<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></span>

</li>

<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.oracle.com/cd/E19253-01/817-5093/fsoverview-43/index.html">"UFS Logging"</a>. <i>Oracle Documentation</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2022-09-27</span></span>.</cite></span>

</li>

<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.openbsd.org/29.html">"OpenBSD 2.9 Release"</a>. <a href="OpenBSD" title="OpenBSD">OpenBSD</a>. 2001-06-01<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></span>

</li>

<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://undeadly.org/cgi?action=article;sid=20230706044554">"Soft updates disabled for future VFS work"</a>. <a href="OpenBSD_Journal" title="OpenBSD Journal">OpenBSD_Journal</a>. 2023-07-05<span class="reference-accessdate">. Retrieved <span class="nowrap">2024-03-09</span></span>.</cite></span>

</li>

<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.openbsd.org/42.html">"OpenBSD 4.2 Release"</a>. OpenBSD. 2007-11-01<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></span>

</li>

<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://marc.info/?l=openbsd-cvs&m=158609976014693&w=2">"Make FFS2 the default filesystem"</a>. OpenBSD. 2020-04-05<span class="reference-accessdate">. Retrieved <span class="nowrap">2020-04-07</span></span>.</cite></span>

</li>

<li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://support.apple.com/kb/HT2316">"Archived — Mac OS X 10.5 Leopard: Installing on a UFS-formatted volume"</a>. <a href="Apple%2C_Inc" class="mw-redirect" title="Apple, Inc">Apple, Inc</a>. 2012-06-12<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></span>

</li>

<li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://discussions.apple.com/message/15668353">"Lion won't mount any disk images with the built-in utility or Disk Utility"</a>. <i>Apple Support Communities</i>. <a href="Apple%2C_Inc" class="mw-redirect" title="Apple, Inc">Apple, Inc</a>. 2011-08-05<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-12-24</span></span>.</cite></span>

</li>

</ol></div>

<div class="mw-heading mw-heading3"><h3 id="Bibliography">Bibliography</h3></div>

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</style><div class="refbegin" style="">

<ul><li><cite id="CITEREFMarshall_Kirk_McKusick,_William_N._Joy,_Samuel_J._Leffler_and_Robert_S._Fabry" class="citation techreport cs1"><a href="Marshall_Kirk_McKusick" title="Marshall Kirk McKusick">Marshall Kirk McKusick</a>, <a href="William_N._Joy" class="mw-redirect" title="William N. Joy">William N. Joy</a>, Samuel J. Leffler and Robert S. Fabry. <a rel="nofollow" class="external text" href="https://www.cs.berkeley.edu/~brewer/cs262/FFS.pdf"><i>A Fast File System for UNIX</i></a> <span class="cs1-format">(PDF)</span> (Technical report). Computer Systems Research Group, Computer Science Division, Department of Electrical Engineering and Computer Science, <a href="University_of_California%2C_Berkeley" title="University of California, Berkeley">University of California, Berkeley</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite><span class="cs1-maint citation-comment"><code class="cs1-code">{{cite tech report}}</code>: CS1 maint: multiple names: authors list (link)</span></li>

<li><cite id="CITEREFMarshall_Kirk_McKusick,_William_N._Joy,_Samuel_J._Leffler_and_Robert_S._Fabry1984" class="citation journal cs1">Marshall Kirk McKusick, William N. Joy, Samuel J. Leffler and Robert S. Fabry (August 1984). <a rel="nofollow" class="external text" href="https://www.cs.cornell.edu/Courses/cs614/2003SP/papers/KJL84.pdf">"A Fast File System for UNIX"</a> <span class="cs1-format">(PDF)</span>. <i>ACM Transactions on Computer Systems</i>. <b>2</b> (3): <span class="nowrap">181–</span>197. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F989.990">10.1145/989.990</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:222285164">222285164</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite><span class="cs1-maint citation-comment"><code class="cs1-code">{{cite journal}}</code>: CS1 maint: multiple names: authors list (link)</span></li>

<li><cite id="CITEREFMarshall_Kirk_McKusickKeith_BosticMichael_J._KarelsJohn_S._Quarterman1996" class="citation book cs1">Marshall Kirk McKusick; Keith Bostic; Michael J. Karels & John S. Quarterman (1996). "Local Filesystems; Local Filestores". <i>The Design and Implementation of the 4.4BSD Operating System</i>. <a href="Addison-Wesley" title="Addison-Wesley">Addison-Wesley</a>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-201-54979-4</bdi>.</cite></li>

<li><cite id="CITEREFMarshall_Kirk_McKusickGregory_R._Ganger1999" class="citation conference cs1">Marshall Kirk McKusick & Gregory R. Ganger (June 1999). <a rel="nofollow" class="external text" href="http://static.usenix.org/publications/library/proceedings/usenix99/full_papers/mckusick/mckusick.pdf">"Soft Updates: A Technique for Eliminating Most Synchronous Writes in the Fast Filesystem"</a> <span class="cs1-format">(PDF)</span>. <i>Proceedings of the FREENIX Track: 1999 USENIX Annual Technical Conference</i>. pp. <span class="nowrap">1–</span>18<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></li>

<li><cite id="CITEREFMarshall_Kirk_McKusick2002" class="citation conference cs1">Marshall Kirk McKusick (February 2002). <a rel="nofollow" class="external text" href="http://static.usenix.org/publications/library/proceedings/bsdcon02/mckusick/mckusick_html/index.html">"Running "fsck" in the Background"</a>. <i>Proceedings of the BSDCon 2002</i>. pp. <span class="nowrap">55–</span>64<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></li>

<li><cite id="CITEREFMarshall_Kirk_McKusick2003" class="citation conference cs1">Marshall Kirk McKusick (September 2003). <a rel="nofollow" class="external text" href="https://www.usenix.org/legacy/events/bsdcon03/tech/full_papers/mckusick/mckusick_html/">"Enhancements to the Fast Filesystem To Support Multi-Terabyte Storage Systems"</a>. <i>Proceedings of the BSDCon 2003</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2019-02-07</span></span>.</cite></li>

<li><cite id="CITEREFRichard_McDougallJim_Mauro2006" class="citation book cs1">Richard McDougall; Jim Mauro (2006). "15: The UFS File System". <a rel="nofollow" class="external text" href="http://ptgmedia.pearsoncmg.com/images/0131482092/samplechapter/mcdougall_ch15.pdf"><i>Solaris Internals: Solaris 10 and OpenSolaris Kernel Architecture</i></a> <span class="cs1-format">(PDF)</span> (2 ed.). Sun Microsystems Press/Prentice Hall. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0-13-148209-2</bdi>.</cite></li></ul>

</div>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><cite id="CITEREFJeroen_C._van_Gelderen2003" class="citation web cs1">Jeroen C. van Gelderen (2003-04-23). <a rel="nofollow" class="external text" href="https://lists.freebsd.org/pipermail/freebsd-current/2003-April/001444.html">"Little UFS2 FAQ"</a>. <a href="FreeBSD" title="FreeBSD">FreeBSD</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2013-04-08</span></span>.</cite></li>

<li><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.tldp.org/HOWTO/Filesystems-HOWTO-9.html#ss9.29">"Filesystems HOWTO: Other filesystems"</a>. <a href="The_Linux_Documentation_Project" class="mw-redirect" title="The Linux Documentation Project">The Linux Documentation Project</a>. 2007-01-27.</cite></li>

<li><a rel="nofollow" class="external text" href="https://www.informit.com/articles/article.aspx?p=605371&seqNum=2">The Solaris UFS File System</a>, see also <a rel="nofollow" class="external autonumber" href="http://ptgmedia.pearsoncmg.com/images/0131482092/samplechapter/mcdougall_ch15.pdf">[1]</a></li>

<li><a rel="nofollow" class="external text" href="http://alter.org.ua/docs/fbsd/ufs/#sb">USF(sic)/UFS2 format</a></li>

<li><a rel="nofollow" class="external text" href="http://pages.cs.wisc.edu/~remzi/OSTEP/file-ffs.pdf">Locality and The Fast File System</a></li></ul>

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</style><div id="File_systems283" style="font-size:114%;margin:0 4em"><a href="File_system" title="File system">File systems</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="2"><div>

<ul><li><a href="Comparison_of_file_systems" title="Comparison of file systems">Comparison of file systems</a>

<ul><li><a href="Comparison_of_distributed_file_systems" title="Comparison of distributed file systems">distributed</a></li></ul></li>

<li><a href="Unix_filesystem" title="Unix filesystem">Unix filesystem</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Disk and<br>non-rotating</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="AdvFS" title="AdvFS">AdvFS</a></li>

<li><a href="Amiga_Fast_File_System" title="Amiga Fast File System">Amiga FFS</a></li>

<li><a href="Amiga_Old_File_System" title="Amiga Old File System">Amiga OFS</a></li>

<li><a href="AtheOS_File_System" class="mw-redirect" title="AtheOS File System">AthFS</a></li>

<li><a href="Bcachefs" title="Bcachefs">bcachefs</a></li>

<li>BFS

<ul><li><a href="Be_File_System" title="Be File System">Be File System</a></li>

<li><a href="Boot_File_System" title="Boot File System">Boot File System</a></li>

<li>Byte File System (<a href="Z/VM" title="Z/VM">z/VM</a>)</li></ul></li>

<li><a href="Btrfs" title="Btrfs">Btrfs</a></li>

<li>EFS

<ul><li><a href="Encrypting_File_System" title="Encrypting File System">Encrypting File System</a></li>

<li><a href="Extent_File_System" title="Extent File System">Extent File System</a></li></ul></li>

<li><a href="Episode_filesystem" title="Episode filesystem">Episode</a></li>

<ul><li><a href="ExFAT" title="ExFAT">exFAT</a></li></ul></li>

<li><a href="Files-11" title="Files-11">Files-11</a></li>

<li><a href="Fossil_(file_system)" title="Fossil (file system)">Fossil</a></li>

<li><a href="HAMMER_(file_system)" title="HAMMER (file system)">HAMMER</a>

<ul><li><a href="HAMMER2" title="HAMMER2">HAMMER2</a></li></ul></li>

<li><a href="Hierarchical_File_System_(Apple)" title="Hierarchical File System (Apple)">HFS</a> (<a href="Classic_Mac_OS" title="Classic Mac OS">Classic Mac OS</a>)</li>

<li>MFS

<ul><li><a href="Macintosh_File_System" title="Macintosh File System">Macintosh File System</a></li>

<li><a href="TiVo_Media_File_System" title="TiVo Media File System">TiVo Media File System</a></li></ul></li>

<li><a href="MINIX_file_system" title="MINIX file system">MINIX</a></li>

<li><a href="NetWare_File_System" title="NetWare File System">NetWare File System</a></li>

<li><a href="NILFS" title="NILFS">NILFS</a>

<ul><li><a href="NILFS" title="NILFS">NILFS2</a></li></ul></li>

<li><a href="OneFS_distributed_file_system" title="OneFS distributed file system">OneFS</a></li>

<li><a href="OpenZFS" title="OpenZFS">OpenZFS</a></li>

<li><a href="ReiserFS" title="ReiserFS">ReiserFS</a>

<ul><li><a href="Reiser4" title="Reiser4">Reiser4</a></li></ul></li>

<li><a href="Datalight#Reliance_family" title="Datalight">Reliance</a></li>

<li><a href="Datalight#Reliance_Nitro" title="Datalight">Reliance Nitro</a></li>

<li>SFS

<ul><li>Shared File System (<a href="VM_(operating_system)" title="VM (operating system)">VM</a>)</li>

<li><a href="Smart_File_System" title="Smart File System">Smart File System</a></li></ul></li>

<li><a href="Soup_(Apple)" title="Soup (Apple)">Soup (Apple)</a></li>

<li><a href="UBIFS" title="UBIFS">UBIFS</a></li>

<li>

<ul><li><a href="Soft_updates" title="Soft updates">soft updates</a></li>

<li><a href="Write_Ahead_Physical_Block_Logging" title="Write Ahead Physical Block Logging">WAPBL</a></li></ul></li>

<li><a href="Xiafs" title="Xiafs">Xiafs</a></li>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Optical_disc" title="Optical disc">Optical disc</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Flash_memory" title="Flash memory">Flash memory</a> and <a href="Solid-state_drive" title="Solid-state drive">SSD</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="ExFAT" title="ExFAT">exFAT</a></li>

<li><a href="EROFS" title="EROFS">EROFS</a></li>

</div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="host-side_wear_leveling27" scope="row" class="navbox-group" style="width:1%">host-side <a href="Wear_leveling" title="Wear leveling">wear leveling</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="LogFS" title="LogFS">LogFS</a></li>

<li><a href="NILFS" title="NILFS">NILFS</a>

<ul><li><a href="NILFS" title="NILFS">NILFS2</a></li></ul></li>

<li><a href="YAFFS" title="YAFFS">YAFFS</a></li>

<li><a href="UBIFS" title="UBIFS">UBIFS</a></li></ul>

</div></td></tr></tbody></table><div>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Clustered_file_system#Distributed_file_systems" title="Clustered file system">Distributed parallel</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="BeeGFS" title="BeeGFS">BeeGFS</a></li>

<li><a href="Google_File_System" title="Google File System">Google File System</a></li>

<li><a href="OrangeFS" title="OrangeFS">OrangeFS</a></li>

</div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Network-attached_storage" title="Network-attached storage">NAS</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Andrew_File_System" title="Andrew File System">AFS</a> (<a href="OpenAFS" title="OpenAFS">OpenAFS</a>)</li>

<li><a href="Google_File_System" title="Google File System">Google File System</a></li>

<li><a href="Lustre_(file_system)" title="Lustre (file system)">Lustre</a></li>

<li><a href="Elliptics" title="Elliptics">POHMELFS</a></li>

<li><a href="Apache_Hadoop" title="Apache Hadoop">Hadoop</a></li>

<li><a href="SSHFS" title="SSHFS">SSHFS</a></li>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Specialized</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Boot_File_System" title="Boot File System">Boot File System</a></li>

<li><a href="Compact_Disc_File_System" title="Compact Disc File System">Compact Disc File System</a></li>

<li><a href="Cramfs" title="Cramfs">cramfs</a></li>

<li><a href="Davfs2" title="Davfs2">Davfs2</a></li>

<li><a href="EROFS" title="EROFS">EROFS</a></li>

<li><a href="FTPFS" title="FTPFS">FTPFS</a></li>

<li><a href="SquashFS" title="SquashFS">SquashFS</a></li>

<li><a href="FAT_filesystem_and_Linux" title="FAT filesystem and Linux">UMSDOS</a></li>

<li><a href="OverlayFS" title="OverlayFS">OverlayFS</a></li>

<li><a href="UnionFS" title="UnionFS">UnionFS</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Pseudo</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Configfs" title="Configfs">configfs</a></li>

<li><a href="Device_file" title="Device file">devfs</a></li>

<li><a href="Debugfs" title="Debugfs">debugfs</a></li>

<li><a href="Kernfs_(BSD)" title="Kernfs (BSD)">kernfs</a></li>

<li><a href="Procfs" title="Procfs">procfs</a></li>

<li>specfs</li>

<li><a href="Sysfs" title="Sysfs">sysfs</a></li>

<li><a href="Tmpfs" title="Tmpfs">tmpfs</a></li>

<li><a href="WinFS" title="WinFS">WinFS</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Filesystem-level_encryption" title="Filesystem-level encryption">Encrypted</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="ECryptfs" title="ECryptfs">eCryptfs</a></li>

<li><a href="EncFS" title="EncFS">EncFS</a></li>

<li><a href="Rubberhose_(file_system)" class="mw-redirect" title="Rubberhose (file system)">Rubberhose</a></li>

<li><a href="SSHFS" title="SSHFS">SSHFS</a></li>

</div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Types</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Clustered_file_system" title="Clustered file system">Clustered</a>

<ul><li><a href="Global_file_system" title="Global file system">Global</a></li>

<li><a href="Self-certifying_File_System" title="Self-certifying File System">Self-certifying</a></li></ul></li>

<li><a href="Flash_file_system" title="Flash file system">Flash</a></li>

<li><a href="Journaling_file_system" title="Journaling file system">Journaling</a></li>

<li><a href="Log-structured_file_system" title="Log-structured file system">Log-structured</a></li>

<li><a href="Object_storage" title="Object storage">Object</a></li>

<li><a href="Record-oriented_filesystem" title="Record-oriented filesystem">Record-oriented</a></li>

<li><a href="Semantic_file_system" title="Semantic file system">Semantic</a></li>

<li><a href="Steganographic_file_system" title="Steganographic file system">Steganographic</a></li>

<li><a href="Synthetic_file_system" title="Synthetic file system">Synthetic</a></li>

<li><a href="Versioning_file_system" title="Versioning file system">Versioning</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Features</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Case_preservation" title="Case preservation">Case preservation</a></li>

<li><a href="Copy-on-write" title="Copy-on-write">Copy-on-write</a></li>

<li><a href="Data_deduplication" title="Data deduplication">Data deduplication</a></li>

<li><a href="Data_scrubbing" title="Data scrubbing">Data scrubbing</a></li>

<li><a href="Execute_in_place" title="Execute in place">Execute in place</a></li>

<li><a href="Extent_(file_systems)" title="Extent (file systems)">Extent</a></li>

<li><a href="File_attribute" title="File attribute">File attribute</a>

<ul><li><a href="Extended_file_attributes" title="Extended file attributes">Extended file attributes</a></li></ul></li>

<li><a href="File_change_log" title="File change log">File change log</a></li>

<li><a href="Inode" title="Inode">Inode</a></li>

<li>Links

<li><a href="Symbolic_link" title="Symbolic link">Symbolic</a></li></ul></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Computer_access_control" title="Computer access control">Access control</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Access-control_list" title="Access-control list">Access-control list</a></li>

<li><a href="Filesystem-level_encryption" title="Filesystem-level encryption">Filesystem-level encryption</a></li>

<li><a href="File-system_permissions" title="File-system permissions">Permissions</a>

<ul><li><a href="Chmod" title="Chmod">Modes</a></li>

<li><a href="Sticky_bit" title="Sticky bit">Sticky bit</a></li></ul></li></ul>

</div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Interface_(computing)" title="Interface (computing)">Interfaces</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="File_manager" title="File manager">File manager</a></li>

<li><a href="File_system_API" title="File system API">File system API</a>

<ul><li><a href="Installable_File_System" title="Installable File System">Installable File System</a></li></ul></li>

<li><a href="Virtual_file_system" title="Virtual file system">Virtual file system</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="List_of_file_systems" title="List of file systems">Lists</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="List_of_cryptographic_file_systems" title="List of cryptographic file systems">Cryptographic</a></li>

<li><a href="List_of_default_file_systems" title="List of default file systems">Default</a></li>

<li><a href="List_of_log-structured_file_systems" title="List of log-structured file systems">Log-structured</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Layouts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Master_Boot_Record" class="mw-redirect" title="Master Boot Record">Master Boot Record</a></li>

<li><a href="GUID_Partition_Table" title="GUID Partition Table">GUID Partition Table</a></li>

<li><a href="Apple_Partition_Map" title="Apple Partition Map">Apple Partition Map</a></li></ul>

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-03-12" href="https://en.wikipedia.org/wiki/?title=Unix_File_System&oldid=1280059008">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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