Repair permissions

<h2 id="overview">Overview</h2>
The <a href="/facts/BSD/XQKcURrh">BSD</a> layer in macOS is responsible for file-system security, including the management of the <a href="/facts/Unix/0pNL2seI">Unix</a> (<a href="/facts/POSIX/mQkSt234">POSIX</a>) <a href="/facts/File_system_permissions/DHq5SwI4">permissions</a> model. Applications depend on the correct assignment and interpretation of permissions in order to function properly.<a class="footnote-ref" id="fnref:2" href="#fn:2">2</a>
Repairing permissions involves checking the permissions of a set of files and folders on a volume with macOS installed against a list of correct POSIX permissions and correcting any discrepancies. The list of correct permissions is compiled by consulting the various bill-of-materials (.bom) files. Typically, these files are stored within reduced-size <a href="/facts/Installer_(macOS)/3uEuffKk">Installer package</a> (.pkg) files in the Receipts folder in the local Library directory (/Library/Receipts) on the volume being checked. Whenever a user installs software that uses the macOS Installer <a href="/facts/Package_format/NWx3JYj7">package format</a>, a bill-of-materials file is created which can be consulted for future permission repair.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a>
Files whose permissions have been incorrectly altered by an administrator, an administrator operating with <a href="/facts/Superuser/0Brr6ol7">root privileges</a>, or a poorly designed installer package (installed with similar privileges) can cause a wide array of problems ranging from application errors to the inability to boot macOS. Repairing permissions can become necessary, but has become increasingly less so for versions after <a href="/facts/Mac_OS_X_Panther/lDrnzKAe">Panther</a> (10.3).<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a>
In <a href="/facts/OS_X_El_Capitan/4NAIbG7c">OS X El Capitan</a>, Apple introduced a security feature called <a href="/facts/System_Integrity_Protection/hpVHcqRh">System Integrity Protection</a>. With it enabled, root privileges are no longer able to change system files and folders, including their permissions. Permissions repairs are instead performed automatically upon system installs and updates.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> To that end, <a href="/facts/Disk_Utility/gcyDN1tx">Disk Utility</a> as well as the corresponding diskutil <a href="/facts/Console_application/Gkr3u58Y">command-line utility</a> lost the ability to repair permissions.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>

<h2 id="usage">Usage</h2>
In systems prior to OS X El Capitan, a permissions repair can be performed by selecting a <a href="/facts/System_partition_and_boot_partition/2pqs8Eqc">startup volume</a> and clicking the "Repair Disk Permissions" button in the "First Aid" section of Disk Utility. The operation can also be performed by using the diskutil command-line utility.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> In El Capitan, the user can instead use two command-line utilities: pkgutil to repair particular packages or /usr/libexec/repair_packages to repair a standard set of system packages.<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a><a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> In both cases, the user has to disable System Integrity Protection to change permissions of system files and directories. In <a href="/facts/MacOS_Sierra/jV5ocHbo">macOS Sierra</a>, /usr/libexec/repair_packages is not available.
Permissions can also be repaired using <a href="/facts/Third-party_software_component/NFlWUV95">third-party utilities</a> such as The Apotek's <a href="/facts/AppleJack/naNa48hF">AppleJack</a> or Prosoft Engineering's Drive Genius.

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Gruber, John. "Seriously, 'Repair Permissions' Is Voodoo". Daring Fireball. John Gruber. Retrieved March 13, 2009. <a href="http://daringfireball.net/2006/04/repair_permissions_voodoo" target="_blank">http://daringfireball.net/2006/04/repair_permissions_voodoo</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">"Security Overview: Permissions". Apple Developer. Archived from the original on June 26, 2004. Retrieved April 4, 2007. <a href="https://web.archive.org/web/20040626052051/http://developer.apple.com/documentation/Security/Conceptual/Security_Overview/Concepts/chapter_3_section_9.html" target="_blank">https://web.archive.org/web/20040626052051/http://developer.apple.com/documentation/Security/Conceptual/Security_Overview/Concepts/chapter_3_section_9.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">"About Disk Utility's Repair Disk Permissions feature". Apple Support. Archived from the original on November 13, 2014. Retrieved April 4, 2007. <a href="https://web.archive.org/web/20141113201431/https://support.apple.com/en-us/HT1452" target="_blank">https://web.archive.org/web/20141113201431/https://support.apple.com/en-us/HT1452</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Gruber, John. "Seriously, 'Repair Permissions' Is Voodoo". Daring Fireball. John Gruber. Retrieved March 13, 2009. <a href="http://daringfireball.net/2006/04/repair_permissions_voodoo" target="_blank">http://daringfireball.net/2006/04/repair_permissions_voodoo</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">"OS X v10.11". Mac Developer Library. Apple Inc. June 8, 2015. Retrieved June 11, 2015. <a href="https://developer.apple.com/library/prerelease/mac/releasenotes/MacOSX/WhatsNewInOSX/Articles/MacOSX10_11.html#//apple_ref/doc/uid/TP40016227-SW1" target="_blank">https://developer.apple.com/library/prerelease/mac/releasenotes/MacOSX/WhatsNewInOSX/Articles/MacOSX10_11.html#//apple_ref/doc/uid/TP40016227-SW1</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">"OS X v10.11 Developer Beta 1 Release Notes". Mac Developer Library. Apple Inc. June 8, 2015. Retrieved June 11, 2015. <a href="https://developer.apple.com/library/prerelease/mac/releasenotes/General/rn-osx-10.11/index.html" target="_blank">https://developer.apple.com/library/prerelease/mac/releasenotes/General/rn-osx-10.11/index.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">diskutil(8) – Darwin and macOS System Manager's Manual <a href="https://keith.github.io/xcode-man-pages/diskutil.8.html" target="_blank">https://keith.github.io/xcode-man-pages/diskutil.8.html</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">pkgutil(1) – Darwin and macOS General Commands Manual <a href="https://keith.github.io/xcode-man-pages/pkgutil.1.html" target="_blank">https://keith.github.io/xcode-man-pages/pkgutil.1.html</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">repair_packages(8) – Darwin and macOS System Manager's Manual <a href="https://keith.github.io/xcode-man-pages/repair_packages.8.html" target="_blank">https://keith.github.io/xcode-man-pages/repair_packages.8.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
</ol>

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Repair permissions