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data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Adoption" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Adoption"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Adoption</span> </div> </a> <ul id="toc-Adoption-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Features" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Features"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Features</span> </div> </a> <ul id="toc-Features-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Limitations" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Limitations"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Limitations</span> </div> </a> <ul id="toc-Limitations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Delayed_allocation_and_potential_data_loss" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Delayed_allocation_and_potential_data_loss"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Delayed allocation and potential data loss</span> </div> </a> <ul id="toc-Delayed_allocation_and_potential_data_loss-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Implementation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Implementation"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Implementation</span> </div> </a> <ul id="toc-Implementation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Interoperability" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Interoperability"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Interoperability</span> </div> </a> <ul id="toc-Interoperability-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-General_Architecture" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#General_Architecture"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>General Architecture</span> </div> </a> <button aria-controls="toc-General_Architecture-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle General Architecture subsection</span> </button> <ul id="toc-General_Architecture-sublist" class="vector-toc-list"> <li id="toc-Superblock" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Superblock"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.1</span> <span>Superblock</span> </div> </a> <ul id="toc-Superblock-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Group_Descriptor_Table" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Group_Descriptor_Table"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.2</span> <span>Group Descriptor Table</span> </div> </a> <ul id="toc-Group_Descriptor_Table-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Block_Bitmap" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Block_Bitmap"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.3</span> <span>Block Bitmap</span> </div> </a> <ul id="toc-Block_Bitmap-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Inode_Bitmap" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Inode_Bitmap"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.4</span> <span>Inode Bitmap</span> </div> </a> <ul id="toc-Inode_Bitmap-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Block_Group_Descriptors" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Block_Group_Descriptors"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.5</span> <span>Block Group Descriptors</span> </div> </a> <ul id="toc-Block_Group_Descriptors-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Flexible_block_groups" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Flexible_block_groups"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Flexible block groups</span> </div> </a> <ul id="toc-Flexible_block_groups-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading">ext4</h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 30 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-30" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">30 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%A5%D9%83%D8%B3_%D8%AA%D9%8A_4" title="إكس تي 4 – Arabic" lang="ar" hreflang="ar" data-title="إكس تي 4" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Ext4" title="Ext4 – Catalan" lang="ca" hreflang="ca" data-title="Ext4" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Ext4" title="Ext4 – Czech" lang="cs" hreflang="cs" data-title="Ext4" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Ext4" title="Ext4 – Danish" lang="da" hreflang="da" data-title="Ext4" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Ext4" title="Ext4 – German" lang="de" hreflang="de" data-title="Ext4" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Ext4" title="Ext4 – Estonian" lang="et" hreflang="et" data-title="Ext4" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Ext4" title="Ext4 – Spanish" lang="es" hreflang="es" data-title="Ext4" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Ext4" title="Ext4 – Esperanto" lang="eo" hreflang="eo" data-title="Ext4" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Ext4" title="Ext4 – Basque" lang="eu" hreflang="eu" data-title="Ext4" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%A7%DB%8C%E2%80%8C%D8%A7%DB%8C%DA%A9%D8%B3%E2%80%8C%D8%AA%DB%8C%DB%B4" title="ای‌ایکس‌تی۴ – Persian" lang="fa" hreflang="fa" data-title="ای‌ایکس‌تی۴" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Ext4" title="Ext4 – French" lang="fr" hreflang="fr" data-title="Ext4" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/Ext4" title="Ext4 – Korean" lang="ko" hreflang="ko" data-title="Ext4" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Ext4" title="Ext4 – Italian" lang="it" hreflang="it" data-title="Ext4" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/Ext4" title="Ext4 – Hebrew" lang="he" hreflang="he" data-title="Ext4" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Ext4" title="Ext4 – Hungarian" lang="hu" hreflang="hu" data-title="Ext4" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Ext4" title="Ext4 – Dutch" lang="nl" hreflang="nl" data-title="Ext4" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/Ext4" title="Ext4 – Japanese" lang="ja" hreflang="ja" data-title="Ext4" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Ext4" title="Ext4 – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Ext4" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Ext4" title="Ext4 – Polish" lang="pl" hreflang="pl" data-title="Ext4" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Ext4" title="Ext4 – Portuguese" lang="pt" hreflang="pt" data-title="Ext4" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Ext4" title="Ext4 – Romanian" lang="ro" hreflang="ro" data-title="Ext4" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/Ext4" title="Ext4 – Russian" lang="ru" hreflang="ru" data-title="Ext4" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Ext4" title="Ext4 – Simple English" lang="en-simple" hreflang="en-simple" data-title="Ext4" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Ext4" title="Ext4 – Slovak" lang="sk" hreflang="sk" data-title="Ext4" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Ext4" title="Ext4 – Finnish" lang="fi" hreflang="fi" data-title="Ext4" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Ext4" title="Ext4 – Swedish" lang="sv" hreflang="sv" data-title="Ext4" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Ext4" title="Ext4 – Turkish" lang="tr" hreflang="tr" data-title="Ext4" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/Ext4" title="Ext4 – Ukrainian" lang="uk" hreflang="uk" data-title="Ext4" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Ext4" title="Ext4 – Vietnamese" lang="vi" hreflang="vi" data-title="Ext4" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/Ext4" title="Ext4 – Chinese" lang="zh" hreflang="zh" data-title="Ext4" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a 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.infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox vevent"><caption class="infobox-title summary">ext4</caption><tbody><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Software_developer" class="mw-redirect" title="Software developer">Developer(s)</a></th><td class="infobox-data">Mingming Cao, Andreas Dilger, Alex Zhuravlev (Tomas), Dave Kleikamp, <a href="/wiki/Theodore_Ts%27o" title="Theodore Ts'o">Theodore Ts'o</a>, Eric Sandeen, Sam Naghshineh, others</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Full name</th><td class="infobox-data">Fourth extended file system</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Introduced</th><td class="infobox-data">10 October 2006 with <a href="/wiki/Linux" title="Linux">Linux</a> 2.6.19</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Preceded by</th><td class="infobox-data"><a href="/wiki/Ext3" title="Ext3">ext3</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Partition_type" title="Partition type">Partition IDs</a></th><td class="infobox-data"><style data-mw-deduplicate="TemplateStyles:r886049734">.mw-parser-output .monospaced{font-family:monospace,monospace}</style><span class="monospaced">0x83</span>: <a href="/wiki/Master_Boot_Record" class="mw-redirect" title="Master Boot Record">MBR</a> / <a href="/wiki/Extended_Boot_Record" class="mw-redirect" title="Extended Boot Record">EBR</a>.<br /> <p><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">EBD0A0A2-B9E5-4433-87C0-68B6B72699C7</span>: <a href="/wiki/GUID_Partition_Table" title="GUID Partition Table">GPT</a> Windows <a href="/wiki/Basic_Data_Partition" class="mw-redirect" title="Basic Data Partition">BDP</a>.<sup id="cite_ref-winbdp_1-0" class="reference"><a href="#cite_note-winbdp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><br /> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">0FC63DAF-8483-4772-8E79-3D69D8477DE4</span>: GPT Linux filesystem data.<sup id="cite_ref-winbdp_1-1" class="reference"><a href="#cite_note-winbdp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><br /> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">933AC7E1-2EB4-4F13-B844-0E14E2AEF915</span>: GPT /home partition.<sup id="cite_ref-DiscoverablePartitionsSpec_2-0" class="reference"><a href="#cite_note-DiscoverablePartitionsSpec-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><br /> </p> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">3B8F8425-20E0-4F3B-907F-1A25A76F98E8</span>: <a href="/wiki/GUID_Partition_Table" title="GUID Partition Table">GPT</a> /srv (server data) partition.</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"><a href="/wiki/Linked_list" title="Linked list">Linked list</a>, hashed <a href="/wiki/B-tree" title="B-tree">B-tree</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">File allocation</th><td class="infobox-data">Extents / Bitmap</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Bad blocks</th><td class="infobox-data">Table</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">1 <a href="/wiki/Exbibyte" class="mw-redirect" title="Exbibyte">EiB</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Max file size</th><td class="infobox-data">16-256 <a href="/wiki/Tebibyte" class="mw-redirect" title="Tebibyte">TiB</a> (for 4-64 KiB block size)</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Max <abbr title="number">no.</abbr> of files</th><td class="infobox-data">4 billion (specified at filesystem creation time)</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Max filename length</th><td class="infobox-data">255 bytes (fewer for multibyte <a href="/wiki/Character_encoding" title="Character encoding">character encodings</a> such as <a href="/wiki/Unicode" title="Unicode">Unicode</a>)</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Allowed filename<br />characters</th><td class="infobox-data">All bytes except <a href="/wiki/Null_character" title="Null character">NULL</a> ('\0') and '/' and the special file names "." and ".." which are not forbidden but are always used for a respective special purpose.</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">modification (mtime), data or attribute modification (ctime), access (atime), delete (dtime), create (crtime)</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Date range</th><td class="infobox-data">14 December 1901 – 10 May 2446<sup id="cite_ref-ext4-timestamp-range_3-0" class="reference"><a href="#cite_note-ext4-timestamp-range-3"><span class="cite-bracket">[</span>3<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">Nanosecond</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Fork_(file_system)" title="Fork (file system)">Forks</a></th><td class="infobox-data">No</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Attributes</th><td class="infobox-data">acl, bh, bsddf, commit=nrsec, data=journal, data=ordered, data=writeback, delalloc, extents, journal_dev, mballoc, minixdf, noacl, nobh, nodelalloc, noextents, nomballoc, nombcache, nouser_xattr, oldalloc, <a href="/wiki/Orlov_block_allocator" title="Orlov block allocator">orlov</a>, user_xattr</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/File_system_permissions" class="mw-redirect" title="File system permissions">File system<br />permissions</a></th><td class="infobox-data">Unix permissions, <a href="/wiki/Access-control_list#POSIX_ACL" title="Access-control list">POSIX ACLs</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Transparent<br />compression</th><td class="infobox-data">No</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Filesystem-level_encryption" title="Filesystem-level encryption">Transparent<br />encryption</a></th><td class="infobox-data">Yes</td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Data_deduplication" title="Data deduplication">Data deduplication</a></th><td class="infobox-data">No</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="/wiki/Operating_system" title="Operating system">operating systems</a></th><td class="infobox-data"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style><div class="plainlist"> <ul><li><a href="/wiki/Linux" title="Linux">Linux</a></li> <li><a href="/wiki/FreeBSD" title="FreeBSD">FreeBSD</a> (full read/write support since version 12.0)</li> <li><a href="/wiki/MacOS" title="MacOS">macOS</a> (read-only with ext4fuse, full with ExtFS)</li> <li><a href="/wiki/Windows" class="mw-redirect" title="Windows">Windows</a> (read–write without <a href="/wiki/Journaling_file_system" title="Journaling file system">journaling</a> with ext2fsd)</li> <li><a href="/wiki/KolibriOS" title="KolibriOS">KolibriOS</a> (read-only)</li></ul> </div></td></tr></tbody></table> <p><b>ext4</b> (<b>fourth extended filesystem</b>) is a <a href="/wiki/Journaling_file_system" title="Journaling file system">journaling file system</a> for <a href="/wiki/Linux" title="Linux">Linux</a>, developed as the successor to <a href="/wiki/Ext3" title="Ext3">ext3</a>. </p><p>ext4 was initially a series of <a href="/wiki/Backward_compatibility" title="Backward compatibility">backward-compatible</a> extensions to ext3, many of them originally developed by Cluster File Systems for the <a href="/wiki/Lustre_(file_system)" title="Lustre (file system)">Lustre file system</a> between 2003 and 2006, meant to extend storage limits and add other performance improvements.<sup id="cite_ref-Mathur_4-0" class="reference"><a href="#cite_note-Mathur-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> However, other <a href="/wiki/Linux_kernel" title="Linux kernel">Linux kernel</a> developers opposed accepting extensions to ext3 for stability reasons,<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> and proposed to <a href="/wiki/Fork_(software_development)" title="Fork (software development)">fork</a> the source code of ext3, rename it as ext4, and perform all the development there, without affecting existing ext3 users. This proposal was accepted, and on 28 June 2006, <a href="/wiki/Theodore_Ts%27o" title="Theodore Ts'o">Theodore Ts'o</a>, the ext3 maintainer, announced the new plan of development for ext4.<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> </p><p>A preliminary development version of ext4 was included in version 2.6.19<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> of the Linux kernel. On 11 October 2008, the patches that mark ext4 as stable code were merged in the Linux 2.6.28 source code repositories,<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> denoting the end of the development phase and recommending ext4 adoption. Kernel 2.6.28, containing the ext4 filesystem, was finally released on 25 December 2008.<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> On 15 January 2010, <a href="/wiki/Google" title="Google">Google</a> announced that it would upgrade its storage infrastructure from <a href="/wiki/Ext2" title="Ext2">ext2</a> to ext4.<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> On 14 December 2010, Google also announced it would use ext4, instead of <a href="/wiki/YAFFS" title="YAFFS">YAFFS</a>, on <a href="/wiki/Android_(operating_system)" title="Android (operating system)">Android 2.3</a>.<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> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Adoption">Adoption</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=1" title="Edit section: Adoption"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>ext4 is the default file system for many Linux distributions including <a href="/wiki/Debian" title="Debian">Debian</a> and <a href="/wiki/Ubuntu" title="Ubuntu">Ubuntu</a>.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Features">Features</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=2" title="Edit section: Features"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed_section plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/60px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/120px-Question_book-new.svg.png 1.5x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Ext4" title="Special:EditPage/Ext4">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a> in this section. Unsourced material may be challenged and removed.</span> <span class="date-container"><i>(<span class="date">May 2024</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <dl><dt>Large file system</dt> <dd>The ext4 filesystem can support volumes with sizes in theory up to 64 <a href="/wiki/Zebibyte" class="mw-redirect" title="Zebibyte">zebibyte (ZiB)</a> and single files with sizes up to 16 <a href="/wiki/Tebibytes" class="mw-redirect" title="Tebibytes">tebibytes (TiB)</a> with the standard 4 <a href="/wiki/Kibibytes" class="mw-redirect" title="Kibibytes">KiB</a> <a href="/wiki/Block_(data_storage)" title="Block (data storage)">block size</a>, and volumes with sizes up to 1 <a href="/wiki/Yobibyte" class="mw-redirect" title="Yobibyte">yobibyte (YiB)</a> with 64 <a href="/wiki/Kibibyte" class="mw-redirect" title="Kibibyte">KiB</a> clusters, though a limitation in the extent format makes 1 <a href="/wiki/Exbibyte" class="mw-redirect" title="Exbibyte">exbibyte (EiB)</a> the practical limit.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> The maximum file, directory, and filesystem size limits grow at least proportionately with the filesystem block size up to the maximum 64 KiB block size available on <a href="/wiki/ARM_Architecture" class="mw-redirect" title="ARM Architecture">ARM</a> and <a href="/wiki/PowerPC" title="PowerPC">PowerPC</a>/<a href="/wiki/Power_ISA" title="Power ISA">Power ISA</a> CPUs.</dd> <dt>Extents</dt> <dd><a href="/wiki/Extent_(file_systems)" title="Extent (file systems)">Extents</a> replace the traditional <a href="/wiki/Block_(data_storage)" title="Block (data storage)">block mapping</a> scheme used by ext2 and ext3. An extent is a range of contiguous physical blocks, improving large-file performance and reducing fragmentation. A single extent in ext4 can map up to 128 <a href="/wiki/Mebibytes" class="mw-redirect" title="Mebibytes">MiB</a> of contiguous space with a 4 KiB block size.<sup id="cite_ref-Mathur_4-1" class="reference"><a href="#cite_note-Mathur-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> There can be four extents stored directly in the <a href="/wiki/Inode" title="Inode">inode</a>. When there are more than four extents to a file, the rest of the extents are indexed in a <a href="/wiki/Tree_(data_structure)" class="mw-redirect" title="Tree (data structure)">tree</a>.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup></dd> <dt>Backward compatibility</dt> <dd>ext4 is <a href="/wiki/Backward-compatible" class="mw-redirect" title="Backward-compatible">backward-compatible</a> with <a href="/wiki/Ext3" title="Ext3">ext3</a> and <a href="/wiki/Ext2" title="Ext2">ext2</a>, making it possible to <a href="/wiki/Mount_(computing)" title="Mount (computing)">mount</a> ext3 and ext2 as ext4. This will slightly improve performance, because certain new features of the ext4 implementation can also be used with ext3 and ext2, such as the new block allocation algorithm, without affecting the on-disk format.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup></dd> <dd>ext3 is partially <a href="/wiki/Forward-compatible" class="mw-redirect" title="Forward-compatible">forward-compatible</a> with ext4. Practically, ext4 will not mount as an ext3 filesystem out of the box, unless certain new features are disabled when creating it, such as <code>^extent</code>, <code>^flex_bg</code>, <code>^huge_file</code>, <code>^uninit_bg</code>, <code>^dir_nlink</code>, and <code>^extra_isize</code>.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup></dd> <dt>Persistent pre-allocation</dt> <dd>ext4 can pre-allocate on-disk space for a file. To do this on most file systems, zeroes would be written to the file when created. In ext4 (and some other file systems such as <a href="/wiki/XFS" title="XFS">XFS</a>) <code>fallocate()</code>, a new system call in the Linux kernel, can be used. The allocated space would be guaranteed and likely contiguous. This situation has applications for media streaming and databases.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (May 2024)">citation needed</span></a></i>]</sup></dd> <dt>Delayed allocation</dt> <dd>ext4 uses a performance technique called <a href="/wiki/Allocate-on-flush" title="Allocate-on-flush">allocate-on-flush</a>, also known as <i>delayed allocation</i>. That is, ext4 delays block allocation until data is flushed to disk; in contrast, some file systems allocate blocks immediately, even when the data goes into a write cache. Delayed allocation improves performance and reduces <a href="/wiki/File_system_fragmentation" title="File system fragmentation">fragmentation</a> by effectively allocating larger amounts of data at a time.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup></dd> <dt>Unlimited number of subdirectories</dt> <dd>ext4 does not limit the number of subdirectories in a single directory, except by the inherent size limit of the directory itself. (In ext3 a directory can have at most 32,000 subdirectories.)<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template noprint Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:AGE_MATTERS" class="mw-redirect" title="Wikipedia:AGE MATTERS"><span title="Written on the page itself. However, the linked page (https://ext4.wiki.kernel.org/index.php/Ext4_Howto#Sub_directory_scalability) doesn't support the claim, instead stating that there is a limit of 64000 subdirs. Take a look at https://man7.org/linux/man-pages/man5/ext4.5.html#FILE_SYSTEM_FEATURES, under dir_nlink (December 2023)">obsolete source</span></a></i>]</sup> To allow for larger directories and continued performance, ext4 in Linux 2.6.23 and later turns on <a href="/wiki/HTree" title="HTree">HTree</a> <a href="/wiki/Array_data_structure" class="mw-redirect" title="Array data structure">indices</a> (a specialized version of a <a href="/wiki/B-tree" title="B-tree">B-tree</a>) by default, which allows directories up to approximately 10–12 million entries to be stored in the 2-level HTree index and 2 GB directory size limit for 4 KiB block size, depending on the filename length. In Linux 4.12 and later the <code>large_dir</code> feature enabled a 3-level HTree and directory sizes over 2 GB, allowing approximately 6 billion entries in a single directory.</dd> <dt>Journal checksums</dt> <dd>ext4 uses <a href="/wiki/Checksum" title="Checksum">checksums</a><sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> in the journal to improve reliability, since the journal is one of the most used files of the disk. This feature has a side benefit: it can safely avoid a disk I/O wait during journaling, improving performance slightly. Journal checksumming was inspired by a research article from the <a href="/wiki/University_of_Wisconsin" class="mw-redirect" title="University of Wisconsin">University of Wisconsin</a>, titled <i>IRON File Systems</i>,<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> with modifications within the implementation of compound transactions performed by the IRON file system (originally proposed by Sam Naghshineh in the RedHat summit).</dd> <dt>Metadata checksumming</dt> <dd>Support for metadata checksums was added in Linux kernel version 3.5 released in 2012.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Many data structures were modified to add <a href="/wiki/CRC-32C" class="mw-redirect" title="CRC-32C">CRC-32C</a> checksums but some only store the lower 16 bits of the 32-bit checksum as there isn't enough previously reserved space to fit the whole 4 bytes. In-place conversion can be done using <code>tune2fs -O metadata_csum</code>.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup></dd> <dt>Faster file-system checking</dt> <dd>In ext4 unallocated block groups and sections of the inode table are marked as such. This enables <a href="/wiki/E2fsck" class="mw-redirect" title="E2fsck">e2fsck</a> to skip them entirely and greatly reduces the time it takes to check the file system. Linux 2.6.24 implements this feature.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (May 2024)">citation needed</span></a></i>]</sup></dd> <dd><figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:E2fsck-uninit.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/E2fsck-uninit.svg/260px-E2fsck-uninit.svg.png" decoding="async" width="260" height="193" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/E2fsck-uninit.svg/390px-E2fsck-uninit.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/63/E2fsck-uninit.svg/520px-E2fsck-uninit.svg.png 2x" data-file-width="389" data-file-height="289" /></a><figcaption><a href="/wiki/Fsck" title="Fsck">fsck</a> time dependence on inode count (<a href="/wiki/Ext3" title="Ext3">ext3</a> vs. ext4)</figcaption></figure></dd> <dt>Multiblock allocator</dt> <dd>When ext3 appends to a file, it calls the block allocator, once for each block. Consequently, if there are multiple concurrent writers, files can easily become <a href="/wiki/File_system_fragmentation" title="File system fragmentation">fragmented</a> on disk. However, ext4 uses delayed allocation, which allows it to buffer data and allocate groups of blocks. Consequently, the multiblock allocator can make better choices about allocating files <a href="/wiki/Contiguous_data_storage" class="mw-redirect" title="Contiguous data storage">contiguously</a> on disk. The multiblock allocator can also be used when files are opened in O_DIRECT mode. This feature does not affect the disk format.</dd> <dt>Improved timestamps</dt> <dd>As computers become faster in general, and as Linux becomes used more for <a href="/wiki/Mission-critical" class="mw-redirect" title="Mission-critical">mission-critical</a> applications, the granularity of second-based timestamps becomes insufficient. To solve this, ext4 provides <a href="/wiki/Timestamp" title="Timestamp">timestamps</a> measured in <a href="/wiki/Nanoseconds" class="mw-redirect" title="Nanoseconds">nanoseconds</a>. In addition, 2 bits of the expanded timestamp field are added to the most significant bits of the seconds field of the timestamps to defer the <a href="/wiki/Year_2038_problem" title="Year 2038 problem">year 2038 problem</a> for an additional 408 years.<sup id="cite_ref-ext4-timestamp-range_3-1" class="reference"><a href="#cite_note-ext4-timestamp-range-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></dd> <dd>ext4 also adds support for time-of-creation timestamps. But, as <a href="/wiki/Theodore_Ts%27o" title="Theodore Ts'o">Theodore Ts'o</a> points out, while it is easy to add an extra creation-date field in the <a href="/wiki/Inode" title="Inode">inode</a> (thus technically enabling support for these timestamps in ext4), it is more difficult to modify or add the necessary <a href="/wiki/System_calls" class="mw-redirect" title="System calls">system calls</a>, like <a href="/wiki/Stat_(Unix)" class="mw-redirect" title="Stat (Unix)">stat()</a> (which would probably require a new version) and the various <a href="/wiki/Library_(computing)" title="Library (computing)">libraries</a> that depend on them (like <a href="/wiki/Glibc" title="Glibc">glibc</a>). These changes will require coordination of many projects.<sup id="cite_ref-osdirmailinglistext4timestamps_24-0" class="reference"><a href="#cite_note-osdirmailinglistext4timestamps-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> Therefore, the creation date stored by ext4 is currently only available to user programs on Linux via the <code>statx()</code> API.<sup id="cite_ref-statx_25-0" class="reference"><a href="#cite_note-statx-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup></dd> <dt>Project quotas</dt> <dd>Support for project quotas was added in Linux kernel 4.4 on 8 Jan 2016. This feature allows assigning <a href="/wiki/Disk_quota" title="Disk quota">disk quota</a> limits to a particular project ID. The project ID of a file is a 32-bit number stored on each file and is inherited by all files and subdirectories created beneath a parent directory with an assigned project ID. This allows assigning quota limits to a particular subdirectory tree independent of file access permissions on the file, such as user and project quotas that are dependent on the UID and GID. While this is similar to a directory quota, the main difference is that the same project ID can be assigned to multiple top-level directories and is not strictly hierarchical.<sup id="cite_ref-projectquota_26-0" class="reference"><a href="#cite_note-projectquota-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup></dd> <dt>Transparent encryption</dt> <dd>Support for transparent encryption was added in Linux kernel 4.1 in June 2015.<sup id="cite_ref-transparentencryption_27-0" class="reference"><a href="#cite_note-transparentencryption-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup></dd> <dt>Lazy initialization</dt> <dd>The lazyinit feature allows cleaning of inode tables in background, speeding initialization when creating a new ext4 file system.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> It is available since 2010 in Linux kernel version 2.6.37.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup></dd> <dt>Write barriers</dt> <dd>ext4 enables write barriers by default. It ensures that file system metadata is correctly written and ordered on disk, even when write caches lose power. This goes with a performance cost especially for applications that use fsync heavily or create and delete many small files. For disks with a battery-backed write cache, disabling barriers (option 'barrier=0') may safely improve performance.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup></dd></dl> <div class="mw-heading mw-heading2"><h2 id="Limitations">Limitations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=3" title="Edit section: Limitations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In 2008, the principal developer of the ext3 and ext4 file systems, <a href="/wiki/Theodore_Ts%27o" title="Theodore Ts'o">Theodore Ts'o</a>, stated that although ext4 has improved features, it is not a major advancement, it uses old technology, and is a stop-gap. Ts'o believes that <a href="/wiki/Btrfs" title="Btrfs">Btrfs</a> is the better direction because "it offers improvements in scalability, reliability, and ease of management".<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> Btrfs also has "a number of the same design ideas that <a href="/wiki/ReiserFS" title="ReiserFS">reiser3</a>/<a href="/wiki/Reiser4" title="Reiser4">4</a> had".<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> However, ext4 has continued to gain new features such as file encryption and metadata checksums. </p><p>The ext4 file system does not honor the "secure deletion" <a href="/wiki/File_attribute" title="File attribute">file attribute</a>, which is supposed to cause overwriting of files upon deletion. A patch to implement secure deletion was proposed in 2011, but did not solve the problem of sensitive data ending up in the file-system journal.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Delayed_allocation_and_potential_data_loss">Delayed allocation and potential data loss</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=4" title="Edit section: Delayed allocation and potential data loss"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Because delayed allocation changes the behavior that programmers have been relying on with ext3, the feature poses some additional risk of data loss in cases where the system crashes or loses power before all of the data has been written to disk. Due to this, ext4 in kernel versions 2.6.30 and later automatically handles these cases as ext3 does. </p><p>The typical scenario in which this might occur is a program replacing the contents of a file without forcing a write to the disk with <a href="/wiki/Fsync" class="mw-redirect" title="Fsync">fsync</a>. There are two common ways of replacing the contents of a file on Unix systems:<sup id="cite_ref-ext4-kerneldoc_34-0" class="reference"><a href="#cite_note-ext4-kerneldoc-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p> <ul><li><code>fd=<a href="/wiki/Open_(system_call)" title="Open (system call)">open</a>("file", O_TRUNC); write(fd, data); close(fd);</code></li></ul> <dl><dd>In this case, an existing file is truncated at the time of open (due to <code>O_TRUNC</code> flag), then new data is written out. Since the write can take some time, there is an opportunity of losing contents even with ext3, but usually very small. However, because ext4 can delay writing file data for a long time, this opportunity is much greater.</dd> <dd>There are several problems that can arise: <ol><li>If the write does not succeed (which may be due to error conditions in the writing program, or due to external conditions such as a full disk), then both the original version <i>and</i> the new version of the file will be lost, and the file may be corrupted because only a part of it has been written.</li> <li>If other processes access the file while it is being written, they see a corrupted version.</li> <li>If other processes have the file open and do not expect its contents to change, those processes may crash. One notable example is a shared library file which is mapped into running programs.</li></ol></dd> <dd>Because of these issues, often the following idiom is preferred over the one above:</dd></dl> <ul><li><code>fd=open("file.new"); write(fd, data); close(fd); <a href="/wiki/Rename_(C)" class="mw-redirect" title="Rename (C)">rename</a>("file.new", "file");</code></li></ul> <dl><dd>A new temporary file ("file.new") is created, which initially contains the new contents. Then the new file is renamed over the old one. Replacing files by the <code>rename()</code> call is guaranteed to be atomic by <a href="/wiki/POSIX" title="POSIX">POSIX</a> standards – i.e. either the old file remains, or it is overwritten with the new one. Because the ext3 default "ordered" journaling mode guarantees file data is written out on disk before metadata, this technique guarantees that either the old or the new file contents will persist on disk. ext4's delayed allocation breaks this expectation, because the file write can be delayed for a long time, and the rename is usually carried out before new file <i>contents</i> reach the disk.</dd></dl> <p>Using <code>fsync()</code> more often to reduce the risk for ext4 could lead to performance penalties on ext3 filesystems mounted with the <code>data=ordered</code> flag (the default on most Linux distributions). Given that both file systems will be in use for some time, this complicates matters for end-user application developers. In response, ext4 in Linux kernels 2.6.30 and newer detect the occurrence of these common cases and force the files to be allocated immediately. For a small cost in performance, this provides semantics similar to ext3 ordered mode and increases the chance that either version of the file will survive the crash. This new behavior is enabled by default, but can be disabled with the "noauto_da_alloc" mount option.<sup id="cite_ref-ext4-kerneldoc_34-1" class="reference"><a href="#cite_note-ext4-kerneldoc-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p>The new patches have become part of the mainline kernel 2.6.30, but various distributions chose to backport them to 2.6.28 or 2.6.29.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p><p>These patches don't completely prevent potential data loss or help at all with new files. The only way to be safe is to write and use software that does <code>fsync()</code> when it needs to. Performance problems can be minimized by limiting crucial disk writes that need <code>fsync()</code> to occur less frequently.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Implementation">Implementation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=5" title="Edit section: Implementation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Simplified_Structure_of_the_Linux_Kernel.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Simplified_Structure_of_the_Linux_Kernel.svg/250px-Simplified_Structure_of_the_Linux_Kernel.svg.png" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Simplified_Structure_of_the_Linux_Kernel.svg/330px-Simplified_Structure_of_the_Linux_Kernel.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/65/Simplified_Structure_of_the_Linux_Kernel.svg/500px-Simplified_Structure_of_the_Linux_Kernel.svg.png 2x" data-file-width="960" data-file-height="540" /></a><figcaption>Simplified structure of the Linux kernel: ext4 is implemented between the Linux kernel Virtual File System and the generic block layer.</figcaption></figure> <p>Linux kernel Virtual File System is a subsystem or layer inside of the Linux kernel. It is the result of an attempt to integrate multiple file systems into an orderly single structure. The key idea, which dates back to the pioneering work done by Sun Microsystems employees in 1986,<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> is to abstract out that part of the file system that is common to all file systems and put that code in a separate layer that calls the underlying concrete file systems to actually manage the data. </p><p>All system calls related to files (or pseudo files) are directed to the Linux kernel Virtual File System for initial processing. These calls, coming from user processes, are the standard POSIX calls, such as <code><a href="/wiki/Open_(system_call)" title="Open (system call)">open</a></code>, <code><a href="/wiki/Read_(system_call)" title="Read (system call)">read</a></code>, <code><a href="/wiki/Write_(system_call)" title="Write (system call)">write</a></code>, <code><a href="/w/index.php?title=Lseek_(system_call)&action=edit&redlink=1" class="new" title="Lseek (system call) (page does not exist)">lseek</a></code>, etc. </p> <div class="mw-heading mw-heading2"><h2 id="Interoperability">Interoperability</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=6" title="Edit section: Interoperability"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Although designed for and primarily used with Linux, an ext4 file system can be accessed via other operating systems via interoperability tools. </p><p><a href="/wiki/Microsoft_Windows" title="Microsoft Windows">Windows</a> provides access via its <a href="/wiki/Windows_Subsystem_for_Linux" title="Windows Subsystem for Linux">Windows Subsystem for Linux</a> (WSL) technology. Specifically, the second major version, WSL 2, is the first version with ext4 support. It was first released in <a href="/wiki/Windows_10_version_history" title="Windows 10 version history">Windows 10 Insider Preview Build 20211</a>.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> WSL 2 requires Windows 10 version 1903 or higher, with build 18362 or higher, for x64 systems, and version 2004 or higher, with build 19041 or higher, for ARM64 systems.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Paragon_Software_Group" title="Paragon Software Group">Paragon Software</a> offers commercial products that provide full read/write access for ext2/3/4 – <i>Linux File Systems for Windows</i><sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> and <i>extFS for Mac</i>.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> </p><p>The free software <i>ext4fuse</i> provides limited (read-only) support. </p> <div class="mw-heading mw-heading2"><h2 id="General_Architecture">General Architecture</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=7" title="Edit section: General Architecture"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The ext4 filesystem divides the partition it resides into smaller chunks called blocks (a group of sectors, usually between 1KiB and 64 KiB). By default, the block size is the same as the page size (4 KiB), but it can be configured with <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">mkfs</span> during filesystem creation. Blocks are grouped into larger chunks called block groups. </p> <div class="mw-heading mw-heading3"><h3 id="Superblock">Superblock</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=8" title="Edit section: Superblock"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Superblock_(file_system)" class="mw-redirect" title="Superblock (file system)">Superblock (file system)</a></div> <p>This is the heart of the filesystem; it resides in only one block of the disk.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> It is usually the first item in a block group, except for group 0, where the first few bytes are reserved for the <a href="/wiki/Boot_sector" title="Boot sector">boot sector</a>. The Superblock is vital for the filesystem – as such, backup copies are written across partitions at filesystem creation time, so it can be recovered in case of corruption. </p> <div class="mw-heading mw-heading3"><h3 id="Group_Descriptor_Table">Group Descriptor Table</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=9" title="Edit section: Group Descriptor Table"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>GDT comes in second after superblock. GDT stores block group descriptors of each block group on the filesystem. It resides on more than one block on disk. Each GDT is 64 bytes in size. This structure is also vital for the filesystem; as such, redundant backups are stored across the filesystem. </p> <div class="mw-heading mw-heading3"><h3 id="Block_Bitmap">Block Bitmap</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=10" title="Edit section: Block Bitmap"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The Block bitmap tracks the block usage status of all blocks of a block group. Each bit in the bitmap represents a block. If a block is in use, its corresponding bit will be set, otherwise it will be unset. The location of the block bitmap is not fixed, so its position is stored in respective block group descriptors. </p> <div class="mw-heading mw-heading3"><h3 id="Inode_Bitmap">Inode Bitmap</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=11" title="Edit section: Inode Bitmap"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Similar to the Block bitmap, the Inode bitmap's location is also not fixed, therefore the group descriptor points to the location of the Inode bitmap. The Inode bitmap tracks usage of inodes. Each bit in the bitmap represents an inode. If an inode is in use then its corresponding bit in Inode bitmap will be set, otherwise it will be unset. </p> <div class="mw-heading mw-heading3"><h3 id="Block_Group_Descriptors">Block Group Descriptors</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=12" title="Edit section: Block Group Descriptors"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Each block group is represented by its block group descriptor. It has vital information for the block group like free <a href="/wiki/Inode" title="Inode">inodes</a>, free blocks and the location of inode bitmap, block bitmap and the inode table of that particular block group. </p> <div class="mw-heading mw-heading2"><h2 id="Flexible_block_groups">Flexible block groups</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=13" title="Edit section: Flexible block groups"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Ext4 introduced flexible block groups. In <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">flex_bg</span>, several block groups are grouped into one logical block group. Block bitmap and inode bitmap of first block group are expanded to include the bitmap and the inode table of other block groups. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Btrfs" title="Btrfs">Btrfs</a> – Copy-on-write file system</li> <li><a href="/wiki/Comparison_of_file_systems" title="Comparison of file systems">Comparison of file systems</a></li> <li><a href="/wiki/Extended_file_attributes" title="Extended file attributes">Extended file attributes</a> – Set of file system features</li> <li><a href="/wiki/E2fsprogs" title="E2fsprogs">e2fsprogs</a> – Software to maintain ext* file systems</li> <li><a href="/wiki/Ext2Fsd" title="Ext2Fsd">Ext2Fsd</a> – Open Source Filesystem driver<span style="display:none" class="category-wikidata-fallback-annotation">Pages displaying wikidata descriptions as a fallback</span></li> <li><a href="/wiki/JFS_(file_system)" title="JFS (file system)">JFS</a> – File system</li> <li><a href="/wiki/List_of_file_systems" title="List of file systems">List of file systems</a></li> <li><a href="/wiki/List_of_default_file_systems" title="List of default file systems">List of default file systems</a></li> <li><a href="/wiki/Reiser4" title="Reiser4">Reiser4</a> – Computer file system, successor to ReiserFS</li> <li><a href="/wiki/XFS" title="XFS">XFS</a> – Journaling file system for IRIX and Linux</li> <li><a href="/wiki/ZFS" title="ZFS">ZFS</a> – Copy-on-write file system</li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=15" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-winbdp-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-winbdp_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-winbdp_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Previously, Linux used the same GUID for the data partitions as Windows (Basic data partition: <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">EBD0A0A2-B9E5-4433-87C0-68B6B72699C7</span>). Linux never had a separate unique partition type GUID defined for its data partitions. This created problems when dual-booting Linux and Windows in UEFI-GPT setup. The new GUID (Linux filesystem data: <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">0FC63DAF-8483-4772-8E79-3D69D8477DE4</span>) was defined jointly by GPT fdisk and GNU Parted developers. It is identified as type code <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734" /><span class="monospaced">0x8300</span> in GPT fdisk. (See definitions in <a rel="nofollow" class="external text" href="http://gptfdisk.git.sourceforge.net/git/gitweb.cgi?p%3Dgptfdisk/gptfdisk;a%3Dblob_plain;f%3Dparttypes.cc;hb%3DHEAD">gdisk's parttypes.cc</a>)</span> </li> <li id="cite_note-DiscoverablePartitionsSpec-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-DiscoverablePartitionsSpec_2-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">"DiscoverablePartitionsSpec"</a>. <i>freedesktop.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">7 April</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=freedesktop.org&rft.atitle=DiscoverablePartitionsSpec&rft_id=http%3A%2F%2Fwww.freedesktop.org%2Fwiki%2FSpecifications%2FDiscoverablePartitionsSpec%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-ext4-timestamp-range-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-ext4-timestamp-range_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ext4-timestamp-range_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=a4dad1ae24f850410c4e60f22823cba1289b8d52">"ext4: Fix handling of extended tv_sec"</a>. Linux-stable kernel tree<span class="reference-accessdate">. Retrieved <span class="nowrap">14 February</span> 2017</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=ext4%3A+Fix+handling+of+extended+tv_sec&rft.pub=Linux-stable+kernel+tree&rft_id=https%3A%2F%2Fgit.kernel.org%2Fcgit%2Flinux%2Fkernel%2Fgit%2Fstable%2Flinux-stable.git%2Fcommit%2F%3Fid%3Da4dad1ae24f850410c4e60f22823cba1289b8d52&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-Mathur-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-Mathur_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Mathur_4-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMathurCaoBhattacharyaDilger2007" class="citation web cs1">Mathur, Avantika; Cao, MingMing; <a href="/wiki/Suparna_Bhattacharya" title="Suparna Bhattacharya">Bhattacharya, Suparna</a>; Dilger, Andreas; Zhuravlev (Tomas), Alex; Vivier, Laurent (2007). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100706040230/http://www.linuxsymposium.org/archives/OLS/Reprints-2007/mathur-Reprint.pdf">"The new ext4 filesystem: current status and future plans"</a> <span class="cs1-format">(PDF)</span>. <i>Proceedings of the Linux Symposium</i>. Ottawa, ON, CA: Red Hat. Archived from <a rel="nofollow" class="external text" href="http://www.linuxsymposium.org/archives/OLS/Reprints-2007/mathur-Reprint.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 6 July 2010<span class="reference-accessdate">. Retrieved <span class="nowrap">15 January</span> 2008</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Proceedings+of+the+Linux+Symposium&rft.atitle=The+new+ext4+filesystem%3A+current+status+and+future+plans&rft.date=2007&rft.aulast=Mathur&rft.aufirst=Avantika&rft.au=Cao%2C+MingMing&rft.au=Bhattacharya%2C+Suparna&rft.au=Dilger%2C+Andreas&rft.au=Zhuravlev+%28Tomas%29%2C+Alex&rft.au=Vivier%2C+Laurent&rft_id=http%3A%2F%2Fwww.linuxsymposium.org%2Farchives%2FOLS%2FReprints-2007%2Fmathur-Reprint.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTorvalds2006" class="citation web cs1">Torvalds, Linus (9 June 2006). <a rel="nofollow" class="external text" href="https://lkml.org/lkml/2006/6/9/183">"extents and 48bit ext3"</a>. <a href="/wiki/Linux_kernel_mailing_list" title="Linux kernel mailing list">Linux kernel mailing list</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=extents+and+48bit+ext3&rft.pub=Linux+kernel+mailing+list&rft.date=2006-06-09&rft.aulast=Torvalds&rft.aufirst=Linus&rft_id=https%3A%2F%2Flkml.org%2Flkml%2F2006%2F6%2F9%2F183&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTs'o2006" class="citation web cs1">Ts'o, Theodore (28 June 2006). <a rel="nofollow" class="external text" href="https://lkml.org/lkml/2006/6/28/454">"Proposal and plan for ext2/3 future development work"</a>. <a href="/wiki/Linux_kernel_mailing_list" title="Linux kernel mailing list">Linux kernel mailing list</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Proposal+and+plan+for+ext2%2F3+future+development+work&rft.pub=Linux+kernel+mailing+list&rft.date=2006-06-28&rft.aulast=Ts%27o&rft.aufirst=Theodore&rft_id=https%3A%2F%2Flkml.org%2Flkml%2F2006%2F6%2F28%2F454&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLeemhuis2008" class="citation news cs1">Leemhuis, Thorsten (23 December 2008). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090103164710/http://www.heise-online.co.uk/open/Kernel-Log-Higher-and-Further-The-innovations-of-Linux-2-6-28--/features/112299">"Higher and further: The innovations of Linux 2.6.28 (page 2)"</a>. Heise Online. Archived from <a rel="nofollow" class="external text" href="http://www.h-online.com/open/features/Kernel-Log-Higher-and-Further-The-innovations-of-Linux-2-6-28-746805.html">the original</a> on 3 January 2009<span class="reference-accessdate">. Retrieved <span class="nowrap">9 January</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Higher+and+further%3A+The+innovations+of+Linux+2.6.28+%28page+2%29&rft.date=2008-12-23&rft.aulast=Leemhuis&rft.aufirst=Thorsten&rft_id=http%3A%2F%2Fwww.h-online.com%2Fopen%2Ffeatures%2FKernel-Log-Higher-and-Further-The-innovations-of-Linux-2-6-28-746805.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://archive.today/20120529150649/http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=03010a3350301baac2154fa66de925ae2981b7e3">"ext4: Rename ext4dev to ext4"</a>. Linus' kernel tree. Archived from <a rel="nofollow" class="external text" href="https://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=03010a3350301baac2154fa66de925ae2981b7e3">the original</a> on 29 May 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">20 October</span> 2008</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=ext4%3A+Rename+ext4dev+to+ext4&rft.pub=Linus%27+kernel+tree&rft_id=https%3A%2F%2Fgit.kernel.org%2F%3Fp%3Dlinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git%3Ba%3Dcommit%3Bh%3D03010a3350301baac2154fa66de925ae2981b7e3&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLeemhuis2008" class="citation news cs1">Leemhuis, Thorsten (23 December 2008). <a rel="nofollow" class="external text" href="http://www.heise-online.co.uk/open/Kernel-Log-Higher-and-Further-The-innovations-of-Linux-2-6-28--/features/112299">"Higher and further: The innovations of Linux 2.6.28"</a>. Heise Online.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Higher+and+further%3A+The+innovations+of+Linux+2.6.28&rft.date=2008-12-23&rft.aulast=Leemhuis&rft.aufirst=Thorsten&rft_id=http%3A%2F%2Fwww.heise-online.co.uk%2Fopen%2FKernel-Log-Higher-and-Further-The-innovations-of-Linux-2-6-28--%2Ffeatures%2F112299&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPaul2010" class="citation web cs1">Paul, Ryan (15 January 2010). <a rel="nofollow" class="external text" href="https://arstechnica.com/open-source/news/2010/01/google-upgrading-to-ext4-hires-former-linux-foundation-cto.ars">"Google upgrading to Ext4, hires former Linux Foundation CTO"</a>. <i>Ars Technica</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Ars+Technica&rft.atitle=Google+upgrading+to+Ext4%2C+hires+former+Linux+Foundation+CTO&rft.date=2010-01-15&rft.aulast=Paul&rft.aufirst=Ryan&rft_id=https%3A%2F%2Farstechnica.com%2Fopen-source%2Fnews%2F2010%2F01%2Fgoogle-upgrading-to-ext4-hires-former-linux-foundation-cto.ars&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation news cs1"><a rel="nofollow" class="external text" href="http://www.h-online.com/open/news/item/Android-2-3-Gingerbread-to-use-Ext4-file-system-1152775.html">"Android 2.3 Gingerbread to use Ext4 file system"</a>. <i>The H Open</i>. 14 December 2010.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+H+Open&rft.atitle=Android+2.3+Gingerbread+to+use+Ext4+file+system&rft.date=2010-12-14&rft_id=http%3A%2F%2Fwww.h-online.com%2Fopen%2Fnews%2Fitem%2FAndroid-2-3-Gingerbread-to-use-Ext4-file-system-1152775.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://wiki.debian.org/FileSystem">"FileSystem in debian"</a>. 14 September 2019.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=FileSystem+in+debian&rft.date=2019-09-14&rft_id=https%3A%2F%2Fwiki.debian.org%2FFileSystem&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.kernel.org/doc/html/v6.1/filesystems/ext4/overview.html#blocks">"ext4 – High Level Design"</a>. <i>kernel.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=kernel.org&rft.atitle=ext4+%E2%80%93+High+Level+Design&rft_id=https%3A%2F%2Fwww.kernel.org%2Fdoc%2Fhtml%2Fv6.1%2Ffilesystems%2Fext4%2Foverview.html%23blocks&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPomeranz2011" class="citation web cs1">Pomeranz, Hal (28 March 2011). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190818050155/https://digital-forensics.sans.org/blog/2011/03/28/digital-forensics-understanding-ext4-part-3-extent-trees">"Understanding EXT4 (Part 3): Extent Trees"</a>. <i>SANS Digital Forensics and Incident Response Blog</i>. Archived from <a rel="nofollow" class="external text" href="https://digital-forensics.sans.org/blog/2011/03/28/digital-forensics-understanding-ext4-part-3-extent-trees">the original</a> on 18 August 2019.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=SANS+Digital+Forensics+and+Incident+Response+Blog&rft.atitle=Understanding+EXT4+%28Part+3%29%3A+Extent+Trees&rft.date=2011-03-28&rft.aulast=Pomeranz&rft.aufirst=Hal&rft_id=https%3A%2F%2Fdigital-forensics.sans.org%2Fblog%2F2011%2F03%2F28%2Fdigital-forensics-understanding-ext4-part-3-extent-trees&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://developer.ibm.com/tutorials/l-anatomy-ext4">"Anatomy of ext4"</a>. <i>IMB Developer</i><span class="reference-accessdate">. Retrieved <span class="nowrap">27 May</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=IMB+Developer&rft.atitle=Anatomy+of+ext4&rft_id=https%3A%2F%2Fdeveloper.ibm.com%2Ftutorials%2Fl-anatomy-ext4&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.linuxquestions.org/questions/red-hat-31/mount-of-ext4-created-without-extents-as-ext3-fails-on-rh6-2-a-936813/">"Mount of ext4 (created without extents) as ext3 fails on RH6.2"</a>. <i>www.linuxquestions.org</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230805062315/https://www.linuxquestions.org/questions/red-hat-31/mount-of-ext4-created-without-extents-as-ext3-fails-on-rh6-2-a-936813/">Archived</a> from the original on 5 August 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.linuxquestions.org&rft.atitle=Mount+of+ext4+%28created+without+extents%29+as+ext3+fails+on+RH6.2&rft_id=http%3A%2F%2Fwww.linuxquestions.org%2Fquestions%2Fred-hat-31%2Fmount-of-ext4-created-without-extents-as-ext3-fails-on-rh6-2-a-936813%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.kernel.org/filesystems/ext4/overview.html#block-and-inode-allocation-policy">"2. High Level Design — The Linux Kernel documentation"</a>. <i>docs.kernel.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">9 January</span> 2025</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=docs.kernel.org&rft.atitle=2.+High+Level+Design+%E2%80%94+The+Linux+Kernel+documentation&rft_id=https%3A%2F%2Fdocs.kernel.org%2Ffilesystems%2Fext4%2Foverview.html%23block-and-inode-allocation-policy&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://kernelnewbies.org/Ext4">"Ext4 – Linux Kernel Newbies"</a>. <i>kernelnewbies.org</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=kernelnewbies.org&rft.atitle=Ext4+%E2%80%93+Linux+Kernel+Newbies&rft_id=https%3A%2F%2Fkernelnewbies.org%2FExt4&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ext4.wiki.kernel.org/index.php/New_ext4_features#Metadata_Checksums">"New ext4 features – Ext4"</a>. <i>ext4.wiki.kernel.org</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230923124620/https://ext4.wiki.kernel.org/index.php/New_ext4_features#Metadata_Checksums">Archived</a> from the original on 23 September 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=ext4.wiki.kernel.org&rft.atitle=New+ext4+features+%E2%80%93+Ext4&rft_id=https%3A%2F%2Fext4.wiki.kernel.org%2Findex.php%2FNew_ext4_features%23Metadata_Checksums&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPrabhakaranBairavasundaramAgrawalGunawi2005" class="citation conference cs1">Prabhakaran, Vijayan; Bairavasundaram, Lakshmi N.; Agrawal, Nitin; Gunawi, Haryadi S.; Arpaci-Dusseau, Andrea C.; Arpaci-Dusseau, Remzi H. (October 2005). <a rel="nofollow" class="external text" href="http://www.cs.wisc.edu/wind/Publications/iron-sosp05.pdf"><i>IRON File Systems</i></a> <span class="cs1-format">(PDF)</span>. <a rel="nofollow" class="external text" href="https://www.sigops.org/s/conferences/sosp/2005/default.htm">Symposium on Operating Systems Principles (SOSP '05)</a>. Brighton, United Kingdom: CS Dept, University of Wisconsin. Section 6.1, Paragraph 5 "Transactional Checksums"<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.btitle=IRON+File+Systems&rft.place=Brighton%2C+United+Kingdom&rft.pages=Section+6.1%2C+Paragraph+5+%22Transactional+Checksums%22&rft.pub=CS+Dept%2C+University+of+Wisconsin&rft.date=2005-10&rft.aulast=Prabhakaran&rft.aufirst=Vijayan&rft.au=Bairavasundaram%2C+Lakshmi+N.&rft.au=Agrawal%2C+Nitin&rft.au=Gunawi%2C+Haryadi+S.&rft.au=Arpaci-Dusseau%2C+Andrea+C.&rft.au=Arpaci-Dusseau%2C+Remzi+H.&rft_id=http%3A%2F%2Fwww.cs.wisc.edu%2Fwind%2FPublications%2Firon-sosp05.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ext4.wiki.kernel.org/index.php/Ext4_Metadata_Checksums">"Ext4 Metadata Checksums – Ext4"</a>. <i>ext4.wiki.kernel.org</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20231106144434/https://ext4.wiki.kernel.org/index.php/Ext4_Metadata_Checksums">Archived</a> from the original on 6 November 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=ext4.wiki.kernel.org&rft.atitle=Ext4+Metadata+Checksums+%E2%80%93+Ext4&rft_id=https%3A%2F%2Fext4.wiki.kernel.org%2Findex.php%2FExt4_Metadata_Checksums&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://kernelnewbies.org/Linux_3.5?highlight=(Metadata)%7C(checksumming)">"Linux_3.5 – Linux Kernel Newbies"</a>. <i>kernelnewbies.org</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=kernelnewbies.org&rft.atitle=Linux_3.5+%E2%80%93+Linux+Kernel+Newbies&rft_id=https%3A%2F%2Fkernelnewbies.org%2FLinux_3.5%3Fhighlight%3D%28Metadata%29%257C%28checksumming%29&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.kernel.org/filesystems/ext4/overview.html#checksums">"2. High Level Design"</a>. <i>The Linux Kernel documentation</i><span class="reference-accessdate">. Retrieved <span class="nowrap">3 April</span> 2025</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Linux+Kernel+documentation&rft.atitle=2.+High+Level+Design&rft_id=https%3A%2F%2Fdocs.kernel.org%2Ffilesystems%2Fext4%2Foverview.html%23checksums&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-osdirmailinglistext4timestamps-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-osdirmailinglistext4timestamps_24-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTs'o2006" class="citation web cs1">Ts'o, Theodore (5 October 2006). <a rel="nofollow" class="external text" href="https://www.redhat.com/archives/ext3-users/2006-October/msg00015.html">"Re: creation time stamps for ext4 ?"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Re%3A+creation+time+stamps+for+ext4+%3F&rft.date=2006-10-05&rft.aulast=Ts%27o&rft.aufirst=Theodore&rft_id=https%3A%2F%2Fwww.redhat.com%2Farchives%2Fext3-users%2F2006-October%2Fmsg00015.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-statx-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-statx_25-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFEdge2017" class="citation web cs1">Edge, Jake (31 March 2017). <a rel="nofollow" class="external text" href="https://lwn.net/Articles/718222/">"Extending statx()"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230920041649/https://lwn.net/Articles/718222/">Archived</a> from the original on 20 September 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Extending+statx%28%29&rft.date=2017-03-31&rft.aulast=Edge&rft.aufirst=Jake&rft_id=https%3A%2F%2Flwn.net%2FArticles%2F718222%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-projectquota-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-projectquota_26-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLi2016" class="citation mailinglist cs1">Li, Xi (12 January 2016). <a rel="nofollow" class="external text" href="https://lwn.net/Articles/671627/">"ext4: add project quota support"</a> (Mailing list). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230920042516/https://lwn.net/Articles/671627/">Archived</a> from the original on 20 September 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=ext4%3A+add+project+quota+support&rft.date=2016-01-12&rft.aulast=Li&rft.aufirst=Xi&rft_id=https%3A%2F%2Flwn.net%2FArticles%2F671627%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-transparentencryption-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-transparentencryption_27-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTs'o2015" class="citation web cs1">Ts'o, Theodore (8 April 2015). <a rel="nofollow" class="external text" href="https://lwn.net/Articles/639427/">"Ext4 encryption"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20231012232912/https://lwn.net/Articles/639427/">Archived</a> from the original on 12 October 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Ext4+encryption&rft.date=2015-04-08&rft.aulast=Ts%27o&rft.aufirst=Theodore&rft_id=https%3A%2F%2Flwn.net%2FArticles%2F639427%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem">"Ext4 Filesystem"</a>. <i>Thomas-Krenn-Wiki</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20220214022131/https://www.thomas-krenn.com/en/wiki/Ext4_Filesystem">Archived</a> from the original on 14 February 2022<span class="reference-accessdate">. Retrieved <span class="nowrap">8 December</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Thomas-Krenn-Wiki&rft.atitle=Ext4+Filesystem&rft_id=https%3A%2F%2Fwww.thomas-krenn.com%2Fen%2Fwiki%2FExt4_Filesystem&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bfff68738f1cb5c93dab1114634cea02aae9e7ba">"kernel/git/torvalds/linux.git – Linux kernel source tree"</a>. <i>git.kernel.org</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=git.kernel.org&rft.atitle=kernel%2Fgit%2Ftorvalds%2Flinux.git+%E2%80%93+Linux+kernel+source+tree&rft_id=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Fcommit%2F%3Fid%3Dbfff68738f1cb5c93dab1114634cea02aae9e7ba&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://wiki.archlinux.org/index.php/ext4#Turning_barriers_off">"Ext4 –"</a>. <i>ArchWiki</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=ArchWiki&rft.atitle=Ext4+%E2%80%93&rft_id=https%3A%2F%2Fwiki.archlinux.org%2Findex.php%2Fext4%23Turning_barriers_off&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-31">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPaul2009" class="citation web cs1">Paul, Ryan (14 April 2009). <a rel="nofollow" class="external text" href="https://arstechnica.com/information-technology/2009/04/linux-collaboration-summit-the-kernel-panel/">"Panelists ponder the kernel at Linux Collaboration Summit"</a>. <i>Ars Technica</i><span class="reference-accessdate">. Retrieved <span class="nowrap">22 August</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Ars+Technica&rft.atitle=Panelists+ponder+the+kernel+at+Linux+Collaboration+Summit&rft.date=2009-04-14&rft.aulast=Paul&rft.aufirst=Ryan&rft_id=https%3A%2F%2Farstechnica.com%2Finformation-technology%2F2009%2F04%2Flinux-collaboration-summit-the-kernel-panel%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTheodore_Ts'o2008" class="citation mailinglist cs1">Theodore Ts'o (1 August 2008). <a rel="nofollow" class="external text" href="https://lkml.org/lkml/2008/8/1/217">"Re: reiser4 for 2.6.27-rc1"</a>. <i>linux-kernel</i> (Mailing list)<span class="reference-accessdate">. Retrieved <span class="nowrap">31 December</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Re%3A+reiser4+for+2.6.27-rc1&rft.date=2008-08-01&rft.au=Theodore+Ts%27o&rft_id=https%3A%2F%2Flkml.org%2Flkml%2F2008%2F8%2F1%2F217&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCorbet2011" class="citation web cs1">Corbet, Jonathan (11 October 2011). <a rel="nofollow" class="external text" href="https://lwn.net/Articles/462437/">"Securely deleting files from ext4 filesystems"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Securely+deleting+files+from+ext4+filesystems&rft.date=2011-10-11&rft.aulast=Corbet&rft.aufirst=Jonathan&rft_id=https%3A%2F%2Flwn.net%2FArticles%2F462437%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-ext4-kerneldoc-34"><span class="mw-cite-backlink">^ <a href="#cite_ref-ext4-kerneldoc_34-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ext4-kerneldoc_34-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.kernel.org/doc/Documentation/filesystems/ext4.txt">"ext4 documentation in Linux kernel source"</a>. 28 March 2009.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=ext4+documentation+in+Linux+kernel+source&rft.date=2009-03-28&rft_id=https%3A%2F%2Fwww.kernel.org%2Fdoc%2FDocumentation%2Ffilesystems%2Fext4.txt&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://bugs.launchpad.net/ubuntu/+source/linux/+bug/317781?comments=all">Ubuntu bug #317781</a> Long discussion between Ubuntu developers and Theodore Ts'o on potential data loss</span> </li> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://thunk.org/tytso/blog/2009/03/12/delayed-allocation-and-the-zero-length-file-problem/">Thoughts by Ted blog entry, 12 March 2009</a> A blog posting of Theodore Ts'o on the subject</span> </li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text">Kleiman</span> </li> <li id="cite_note-38"><span class="mw-cite-backlink"><b><a href="#cite_ref-38">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBrandon_LeBlanc2020" class="citation web cs1">Brandon LeBlanc (10 September 2020). <a rel="nofollow" class="external text" href="https://blogs.windows.com/windows-insider/2020/09/10/announcing-windows-10-insider-preview-build-20211/">"Announcing Windows 10 Insider Preview Build 20211"</a>. <i>Windows Blogs</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 May</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Windows+Blogs&rft.atitle=Announcing+Windows+10+Insider+Preview+Build+20211&rft.date=2020-09-10&rft.au=Brandon+LeBlanc&rft_id=https%3A%2F%2Fblogs.windows.com%2Fwindows-insider%2F2020%2F09%2F10%2Fannouncing-windows-10-insider-preview-build-20211%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-39"><span class="mw-cite-backlink"><b><a href="#cite_ref-39">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPierre_Boulay2020" class="citation web cs1">Pierre Boulay (10 September 2020). <a rel="nofollow" class="external text" href="https://devblogs.microsoft.com/commandline/access-linux-filesystems-in-windows-and-wsl-2/">"Access Linux filesystems in Windows and WSL 2"</a>. <i>Windows Command Line</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 May</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Windows+Command+Line&rft.atitle=Access+Linux+filesystems+in+Windows+and+WSL+2&rft.date=2020-09-10&rft.au=Pierre+Boulay&rft_id=https%3A%2F%2Fdevblogs.microsoft.com%2Fcommandline%2Faccess-linux-filesystems-in-windows-and-wsl-2%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-40">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.microsoft.com/en-gb/windows/wsl/wsl2-mount-disk">"Get started mounting a Linux disk in WSL 2"</a>. <i>Microsoft Docs</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 May</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Microsoft+Docs&rft.atitle=Get+started+mounting+a+Linux+disk+in+WSL+2&rft_id=https%3A%2F%2Fdocs.microsoft.com%2Fen-gb%2Fwindows%2Fwsl%2Fwsl2-mount-disk&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-41"><span class="mw-cite-backlink"><b><a href="#cite_ref-41">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCraig_Loewen2019" class="citation web cs1">Craig Loewen (12 June 2019). <a rel="nofollow" class="external text" href="https://devblogs.microsoft.com/commandline/wsl-2-is-now-available-in-windows-insiders/">"WSL 2 is now available in Windows Insiders"</a>. <i>Windows Command Line</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 May</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Windows+Command+Line&rft.atitle=WSL+2+is+now+available+in+Windows+Insiders&rft.date=2019-06-12&rft.au=Craig+Loewen&rft_id=https%3A%2F%2Fdevblogs.microsoft.com%2Fcommandline%2Fwsl-2-is-now-available-in-windows-insiders%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-42"><span class="mw-cite-backlink"><b><a href="#cite_ref-42">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.microsoft.com/en-gb/windows/wsl/install-win10">"Windows Subsystem for Linux Installation Guide for Windows 10"</a>. <i>Windows Docs</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 May</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Windows+Docs&rft.atitle=Windows+Subsystem+for+Linux+Installation+Guide+for+Windows+10&rft_id=https%3A%2F%2Fdocs.microsoft.com%2Fen-gb%2Fwindows%2Fwsl%2Finstall-win10&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-43"><span class="mw-cite-backlink"><b><a href="#cite_ref-43">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.paragon-software.com/home/linuxfs-windows/">"Linux File Systems for Windows"</a>. <i>Paragon Software</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 May</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Paragon+Software&rft.atitle=Linux+File+Systems+for+Windows&rft_id=https%3A%2F%2Fwww.paragon-software.com%2Fhome%2Flinuxfs-windows%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-44"><span class="mw-cite-backlink"><b><a href="#cite_ref-44">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.paragon-software.com/home/extfs-mac/">"extFS for Mac"</a>. <i>Paragon Software</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 May</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Paragon+Software&rft.atitle=extFS+for+Mac&rft_id=https%3A%2F%2Fwww.paragon-software.com%2Fhome%2Fextfs-mac%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AExt4" class="Z3988"></span></span> </li> <li id="cite_note-45"><span class="mw-cite-backlink"><b><a href="#cite_ref-45">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external free" href="https://docs.kernel.org/filesystems/ext4/overview.html#layout">https://docs.kernel.org/filesystems/ext4/overview.html#layout</a></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Ext4&action=edit&section=16" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://www.kernel.org/doc/Documentation/filesystems/ext4.txt">ext4 documentation in Linux kernel source</a></li> <li><a rel="nofollow" class="external text" href="https://archive.today/20120712143749/kerneltrap.org/node/6776">Theodore Ts'o's discussion on ext4</a>, 29 June 2006</li> <li><a rel="nofollow" class="external text" href="https://ols.fedoraproject.org/OLS/Reprints-2007/sato-Reprint.pdf">"ext4 online defragmentation"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20191230032039/https://ols.fedoraproject.org/OLS/Reprints-2007/sato-Reprint.pdf">Archived</a> 30 December 2019 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> (materials from Ottawa Linux Symposium 2007)</li> <li><a rel="nofollow" class="external text" href="https://www.kernel.org/doc/ols/2007/ols2007v2-pages-21-34.pdf">"The new ext4 filesystem: current status and future plans"</a> (materials from Ottawa Linux Symposium 2007)</li> <li><a rel="nofollow" class="external text" href="http://heise-online.co.uk/news/Kernel-Log-Ext4-completes-development-phase-as-interim-step-to-btrfs--/111742">Kernel Log: Ext4 completes development phase as interim step to btrfs</a>, 17 October 2008</li> <li><a rel="nofollow" class="external text" href="https://ols.fedoraproject.org/OLS/Reprints-2008/kumar-reprint.pdf">"Ext4 block and inode allocator improvements"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100331074732/http://ols.fedoraproject.org/OLS/Reprints-2008/kumar-reprint.pdf">Archived</a> 31 March 2010 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> (materials from Ottawa Linux Symposium 2008)</li> <li><a rel="nofollow" class="external text" href="http://usenix.org/event/lsf07/tech/cao_m.pdf">"Ext4: The Next Generation of Ext2/3 Filesystem"</a></li> <li><a rel="nofollow" class="external text" href="https://ext4.wiki.kernel.org/">Ext4 (and Ext2/Ext3) Wiki</a></li> <li><a rel="nofollow" class="external text" href="http://kernelnewbies.org/Ext4">Ext4</a> wiki at kernelnewbies.org</li> <li>Native Windows port of Ext4 and other FS in <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120111062641/http://www.crossmeta.org/redmine">CROSSMETA</a></li> <li><a rel="nofollow" class="external text" href="http://ext2read.sourceforge.net/">Ext2read</a> A windows application to read/copy ext2/ext3/ext4 files with extent and LVM2 support.</li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20120723091043/http://www.ext2fsd.com/">Ext2Fsd</a> Open source ext2/ext3/ext4 read/write file system driver for Windows. ext4 is supported from version 0.50 onwards</li> <li><a rel="nofollow" class="external text" href="https://github.com/gerard/ext4fuse">Ext4fuse</a> Open source read-only ext4 driver for <a href="/wiki/Filesystem_in_Userspace" title="Filesystem in Userspace">FUSE</a>. (Supports <a href="/wiki/Mac_OS_X" class="mw-redirect" title="Mac OS X">Mac OS X</a> 10.5 and later, using <a rel="nofollow" class="external text" href="https://code.google.com/p/macfuse/">MacFuse</a>)</li> <li><a rel="nofollow" class="external text" href="https://blogs.oracle.com/linux/post/understanding-ext4-disk-layout-part-1">oracle post</a> Understanding ext4 disk layout</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist 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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="/wiki/Advanced_Disc_Filing_System" title="Advanced Disc Filing System">ADFS</a></li> <li><a href="/wiki/AdvFS" title="AdvFS">AdvFS</a></li> <li><a href="/wiki/Amiga_Fast_File_System" title="Amiga Fast File System">Amiga FFS</a></li> <li><a href="/wiki/Amiga_Old_File_System" title="Amiga Old File System">Amiga OFS</a></li> <li><a href="/wiki/Apple_File_System" title="Apple File System">APFS</a></li> <li><a href="/wiki/AtheOS_File_System" class="mw-redirect" title="AtheOS File System">AthFS</a></li> <li><a href="/wiki/Bcachefs" title="Bcachefs">bcachefs</a></li> <li>BFS <ul><li><a href="/wiki/Be_File_System" title="Be File System">Be File System</a></li> <li><a href="/wiki/Boot_File_System" title="Boot File System">Boot File System</a></li> <li>Byte File System (<a href="/wiki/Z/VM" title="Z/VM">z/VM</a>)</li></ul></li> <li><a href="/wiki/Btrfs" title="Btrfs">Btrfs</a></li> <li><a href="/wiki/StorNext_File_System" title="StorNext File System">CVFS</a></li> <li><a href="/wiki/CXFS" title="CXFS">CXFS</a></li> <li><a href="/wiki/Disc_Filing_System" title="Disc Filing System">DFS</a></li> <li>EFS <ul><li><a href="/wiki/Encrypting_File_System" title="Encrypting File System">Encrypting File System</a></li> <li><a href="/wiki/Extent_File_System" title="Extent File System">Extent File System</a></li></ul></li> <li><a href="/wiki/Episode_filesystem" title="Episode filesystem">Episode</a></li> <li><a href="/wiki/Extended_file_system" title="Extended file system">ext</a> <ul><li><a href="/wiki/Ext2" title="Ext2">ext2</a></li> <li><a href="/wiki/Ext3" title="Ext3">ext3</a></li> <li><a href="/wiki/Ext3cow" title="Ext3cow">ext3cow</a></li> <li><a class="mw-selflink selflink">ext4</a></li></ul></li> <li><a href="/wiki/File_Allocation_Table" title="File Allocation Table">FAT</a> <ul><li><a href="/wiki/ExFAT" title="ExFAT">exFAT</a></li></ul></li> <li><a href="/wiki/Files-11" title="Files-11">Files-11</a></li> <li><a href="/wiki/Fossil_(file_system)" title="Fossil (file system)">Fossil</a></li> <li><a href="/wiki/GPFS" title="GPFS">GPFS</a></li> <li><a href="/wiki/HAMMER_(file_system)" title="HAMMER (file system)">HAMMER</a> <ul><li><a href="/wiki/HAMMER2" title="HAMMER2">HAMMER2</a></li></ul></li> <li><a href="/wiki/Hierarchical_File_System_(Apple)" title="Hierarchical File System (Apple)">HFS</a> (<a href="/wiki/Classic_Mac_OS" title="Classic Mac OS">Classic Mac OS</a>)</li> <li><a href="/wiki/Hierarchical_File_System_(IBM_MVS)" title="Hierarchical File System (IBM MVS)">HFS</a> (<a href="/wiki/MVS" title="MVS">MVS</a>)</li> <li><a href="/wiki/HFS_Plus" title="HFS Plus">HFS+</a></li> <li><a href="/wiki/High_Performance_File_System" title="High Performance File System">HPFS</a></li> <li><a href="/wiki/High_Throughput_File_System" title="High Throughput File System">HTFS</a></li> <li><a href="/wiki/JFS_(file_system)" title="JFS (file system)">JFS</a></li> <li><a href="/wiki/Log-structured_File_System_(BSD)" title="Log-structured File System (BSD)">LFS</a></li> <li>MFS <ul><li><a href="/wiki/Macintosh_File_System" title="Macintosh File System">Macintosh File System</a></li> <li><a href="/wiki/TiVo_Media_File_System" title="TiVo Media File System">TiVo Media File System</a></li></ul></li> <li><a href="/wiki/MINIX_file_system" title="MINIX file system">MINIX</a></li> <li><a href="/wiki/NetWare_File_System" title="NetWare File System">NetWare File System</a></li> <li><a href="/wiki/Next3" title="Next3">Next3</a></li> <li><a href="/wiki/NILFS" title="NILFS">NILFS</a> <ul><li><a href="/wiki/NILFS" title="NILFS">NILFS2</a></li></ul></li> <li><a href="/wiki/Novell_Storage_Services" title="Novell Storage Services">NSS</a></li> <li><a href="/wiki/NTFS" title="NTFS">NTFS</a></li> <li><a href="/wiki/OneFS_distributed_file_system" title="OneFS distributed file system">OneFS</a></li> <li><a href="/wiki/OpenZFS" title="OpenZFS">OpenZFS</a></li> <li><a href="/wiki/Professional_File_System" title="Professional File System">PFS</a></li> <li><a href="/wiki/QFS" title="QFS">QFS</a></li> <li><a href="/wiki/QNX4FS" title="QNX4FS">QNX4FS</a></li> <li><a href="/wiki/ReFS" title="ReFS">ReFS</a></li> <li><a href="/wiki/ReiserFS" title="ReiserFS">ReiserFS</a> <ul><li><a href="/wiki/Reiser4" title="Reiser4">Reiser4</a></li></ul></li> <li><a href="/wiki/Datalight#Reliance_family" title="Datalight">Reliance</a></li> <li><a href="/wiki/Datalight#Reliance_Nitro" title="Datalight">Reliance Nitro</a></li> <li><a href="/wiki/Remote_File_Sharing" title="Remote File Sharing">RFS</a></li> <li>SFS <ul><li>Shared File System (<a href="/wiki/VM_(operating_system)" title="VM (operating system)">VM</a>)</li> <li><a href="/wiki/Smart_File_System" title="Smart File System">Smart File System</a></li></ul></li> <li><a href="/wiki/StorNext_File_System" title="StorNext File System">SNFS</a></li> <li><a href="/wiki/Soup_(Apple)" title="Soup (Apple)">Soup (Apple)</a></li> <li><a href="/wiki/Tux3" title="Tux3">Tux3</a></li> <li><a href="/wiki/UBIFS" title="UBIFS">UBIFS</a></li> <li><a href="/wiki/Unix_File_System" title="Unix File System">UFS/UFS2</a> <ul><li><a href="/wiki/Soft_updates" title="Soft updates">soft updates</a></li> <li><a href="/wiki/Write_Ahead_Physical_Block_Logging" title="Write Ahead Physical Block Logging">WAPBL</a></li></ul></li> <li><a href="/wiki/Veritas_File_System" title="Veritas File System">VxFS</a></li> <li><a href="/wiki/Write_Anywhere_File_Layout" title="Write Anywhere File Layout">WAFL</a></li> <li><a href="/wiki/Xiafs" title="Xiafs">Xiafs</a></li> <li><a href="/wiki/XFS" title="XFS">XFS</a></li> <li><a href="/wiki/Xsan" title="Xsan">Xsan</a></li> <li><a href="/wiki/ZFS_(z/OS_file_system)" title="ZFS (z/OS file system)">zFS</a> (<a href="/wiki/Z/OS" title="Z/OS">z/OS</a>)</li> <li><a href="/wiki/ZFS" title="ZFS">ZFS</a> (<a href="/wiki/Sun_Microsystems" title="Sun Microsystems">Sun</a>)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/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"> <ul><li><a href="/wiki/High_Sierra_Format" class="mw-redirect" title="High Sierra Format">HSF</a></li> <li><a href="/wiki/ISO_9660" title="ISO 9660">ISO 9660</a></li> <li><a href="/wiki/ISO_13490" title="ISO 13490">ISO 13490</a></li> <li><a href="/wiki/Universal_Disk_Format" title="Universal Disk Format">UDF</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Flash_memory" title="Flash memory">Flash memory</a> and <a href="/wiki/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"> <ul><li><a href="/wiki/Apple_File_System" title="Apple File System">APFS</a></li> <li><a href="/wiki/File_Allocation_Table" title="File Allocation Table">FAT</a></li> <li><a href="/wiki/ExFAT" title="ExFAT">exFAT</a></li> <li><a href="/wiki/Transaction-Safe_FAT_File_System" title="Transaction-Safe FAT File System">TFAT</a></li> <li><a href="/wiki/EROFS" title="EROFS">EROFS</a></li> <li><a href="/wiki/F2FS" title="F2FS">F2FS</a></li> <li><a href="/wiki/JFS_(file_system)" title="JFS (file system)">JFS</a></li> <li><a href="/wiki/Non-Volatile_File_System" title="Non-Volatile File System">NVFS</a></li></ul> </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="/wiki/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"> <ul><li><a href="/wiki/CHFS" title="CHFS">CHFS</a></li> <li><a href="/wiki/JFFS" title="JFFS">JFFS</a></li> <li><a href="/wiki/JFFS2" title="JFFS2">JFFS2</a></li> <li><a href="/wiki/LogFS" title="LogFS">LogFS</a></li> <li><a href="/wiki/NILFS" title="NILFS">NILFS</a> <ul><li><a href="/wiki/NILFS" title="NILFS">NILFS2</a></li></ul></li> <li><a href="/wiki/YAFFS" title="YAFFS">YAFFS</a></li> <li><a href="/wiki/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="/wiki/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="/wiki/BeeGFS" title="BeeGFS">BeeGFS</a></li> <li><a href="/wiki/Ceph_(software)" title="Ceph (software)">Ceph</a></li> <li><a href="/wiki/CXFS" title="CXFS">CXFS</a></li> <li><a href="/wiki/GFS2" title="GFS2">GFS2</a></li> <li><a href="/wiki/Google_File_System" title="Google File System">Google File System</a></li> <li><a href="/wiki/OCFS2" title="OCFS2">OCFS2</a></li> <li><a href="/wiki/OrangeFS" title="OrangeFS">OrangeFS</a></li> <li><a href="/wiki/Parallel_Virtual_File_System" title="Parallel Virtual File System">PVFS</a></li> <li><a href="/wiki/Quantcast_File_System" title="Quantcast File System">QFS</a></li> <li><a href="/wiki/Xsan" title="Xsan">Xsan</a></li> <li><i><a href="/wiki/List_of_file_systems#Distributed_parallel_file_systems" title="List of file systems">more...</a></i></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/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"> <ul><li><a href="/wiki/9P_(protocol)" title="9P (protocol)">9P</a></li> <li><a href="/wiki/Andrew_File_System" title="Andrew File System">AFS</a> (<a href="/wiki/OpenAFS" title="OpenAFS">OpenAFS</a>)</li> <li><a href="/wiki/Apple_Filing_Protocol" title="Apple Filing Protocol">AFP</a></li> <li><a href="/wiki/Coda_(file_system)" title="Coda (file system)">Coda</a></li> <li><a href="/wiki/Distributed_File_System_(Microsoft)" title="Distributed File System (Microsoft)">DFS</a></li> <li><a href="/wiki/Google_File_System" title="Google File System">Google File System</a></li> <li><a href="/wiki/GPFS" title="GPFS">GPFS</a></li> <li><a href="/wiki/Lustre_(file_system)" title="Lustre (file system)">Lustre</a></li> <li><a href="/wiki/NetWare_Core_Protocol" title="NetWare Core Protocol">NCP</a></li> <li><a href="/wiki/Network_File_System" title="Network File System">NFS</a></li> <li><a href="/wiki/Elliptics" title="Elliptics">POHMELFS</a></li> <li><a href="/wiki/Apache_Hadoop" title="Apache Hadoop">Hadoop</a></li> <li><a href="/wiki/Server_Message_Block" title="Server Message Block">SMB (CIFS)</a></li> <li><a href="/wiki/SSHFS" title="SSHFS">SSHFS</a></li> <li><i><a href="/wiki/List_of_file_systems#Distributed_file_systems" title="List of file systems">more...</a></i></li></ul> </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"> <ul><li><a href="/wiki/Aufs" title="Aufs">Aufs</a></li> <li><a href="/wiki/AXFS" title="AXFS">AXFS</a></li> <li><a href="/wiki/Boot_File_System" title="Boot File System">Boot File System</a></li> <li><a href="/wiki/Compact_Disc_File_System" title="Compact Disc File System">Compact Disc File System</a></li> <li><a href="/wiki/Cramfs" title="Cramfs">cramfs</a></li> <li><a href="/wiki/Davfs2" title="Davfs2">Davfs2</a></li> <li><a href="/wiki/EROFS" title="EROFS">EROFS</a></li> <li><a href="/wiki/FTPFS" title="FTPFS">FTPFS</a></li> <li><a href="/wiki/Filesystem_in_Userspace" title="Filesystem in Userspace">FUSE</a></li> <li><a href="/wiki/Lnfs" title="Lnfs">Lnfs</a></li> <li><a href="/wiki/Linear_Tape_File_System" title="Linear Tape File System">LTFS</a></li> <li><a href="/wiki/NOVA_(filesystem)" title="NOVA (filesystem)">NOVA</a></li> <li><a href="/wiki/Rational_MultiVersion_File_System" class="mw-redirect" title="Rational MultiVersion File System">MVFS</a></li> <li><a href="/wiki/SquashFS" title="SquashFS">SquashFS</a></li> <li><a href="/wiki/FAT_filesystem_and_Linux" title="FAT filesystem and Linux">UMSDOS</a></li> <li><a href="/wiki/OverlayFS" title="OverlayFS">OverlayFS</a></li> <li><a href="/wiki/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="/wiki/Configfs" title="Configfs">configfs</a></li> <li><a href="/wiki/Device_file" title="Device file">devfs</a></li> <li><a href="/wiki/Debugfs" title="Debugfs">debugfs</a></li> <li><a href="/wiki/Kernfs_(BSD)" title="Kernfs (BSD)">kernfs</a></li> <li><a href="/wiki/Procfs" title="Procfs">procfs</a></li> <li>specfs</li> <li><a href="/wiki/Sysfs" title="Sysfs">sysfs</a></li> <li><a href="/wiki/Tmpfs" title="Tmpfs">tmpfs</a></li> <li><a href="/wiki/WinFS" title="WinFS">WinFS</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/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="/wiki/ECryptfs" title="ECryptfs">eCryptfs</a></li> <li><a href="/wiki/EncFS" title="EncFS">EncFS</a></li> <li><a href="/wiki/Encrypting_File_System" title="Encrypting File System">EFS</a></li> <li><a href="/wiki/Rubberhose_(file_system)" class="mw-redirect" title="Rubberhose (file system)">Rubberhose</a></li> <li><a href="/wiki/SSHFS" title="SSHFS">SSHFS</a></li> <li><a href="/wiki/Oracle_ZFS" title="Oracle ZFS">ZFS</a></li></ul> </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="/wiki/Clustered_file_system" title="Clustered file system">Clustered</a> <ul><li><a href="/wiki/Global_file_system" title="Global file system">Global</a></li> <li><a href="/wiki/Grid_file_system" title="Grid file system">Grid</a></li> <li><a href="/wiki/Self-certifying_File_System" title="Self-certifying File System">Self-certifying</a></li></ul></li> <li><a href="/wiki/Flash_file_system" title="Flash file system">Flash</a></li> <li><a href="/wiki/Journaling_file_system" title="Journaling file system">Journaling</a></li> <li><a href="/wiki/Log-structured_file_system" title="Log-structured file system">Log-structured</a></li> <li><a href="/wiki/Object_storage" title="Object storage">Object</a></li> <li><a href="/wiki/Record-oriented_filesystem" title="Record-oriented filesystem">Record-oriented</a></li> <li><a href="/wiki/Semantic_file_system" title="Semantic file system">Semantic</a></li> <li><a href="/wiki/Steganographic_file_system" title="Steganographic file system">Steganographic</a></li> <li><a href="/wiki/Synthetic_file_system" title="Synthetic file system">Synthetic</a></li> <li><a href="/wiki/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="/wiki/Case_preservation" title="Case preservation">Case preservation</a></li> <li><a href="/wiki/Copy-on-write" title="Copy-on-write">Copy-on-write</a></li> <li><a href="/wiki/Data_deduplication" title="Data deduplication">Data deduplication</a></li> <li><a href="/wiki/Data_scrubbing" title="Data scrubbing">Data scrubbing</a></li> <li><a href="/wiki/Execute_in_place" title="Execute in place">Execute in place</a></li> <li><a href="/wiki/Extent_(file_systems)" title="Extent (file systems)">Extent</a></li> <li><a href="/wiki/File_attribute" title="File attribute">File attribute</a> <ul><li><a href="/wiki/Extended_file_attributes" title="Extended file attributes">Extended file attributes</a></li></ul></li> <li><a href="/wiki/File_change_log" title="File change log">File change log</a></li> <li><a href="/wiki/Fork_(file_system)" title="Fork (file system)">Fork</a></li> <li><a href="/wiki/Inode" title="Inode">Inode</a></li> <li>Links <ul><li><a href="/wiki/Hard_link" title="Hard link">Hard</a></li> <li><a href="/wiki/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="/wiki/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="/wiki/Access-control_list" title="Access-control list">Access-control list</a></li> <li><a href="/wiki/Filesystem-level_encryption" title="Filesystem-level encryption">Filesystem-level encryption</a></li> <li><a href="/wiki/File-system_permissions" title="File-system permissions">Permissions</a> <ul><li><a href="/wiki/Chmod" title="Chmod">Modes</a></li> <li><a href="/wiki/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="/wiki/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="/wiki/File_manager" title="File manager">File manager</a></li> <li><a href="/wiki/File_system_API" title="File system API">File system API</a> <ul><li><a href="/wiki/Installable_File_System" title="Installable File System">Installable File System</a></li></ul></li> <li><a href="/wiki/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="/wiki/List_of_file_systems" title="List of 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