Repair permissions

Repair permissions

Repairing disk permissions is a troubleshooting activity commonly associated with the Mac OS X operating system.


The BSD layer in Mac OS X (and Darwin) is responsible for filesystem security, including the management of the Unix (POSIX) permissions model. Applications depend on the correct assignment and interpretation of permissions in order to function properly. [cite web | title=Apple - Developer - Security Overview: Permissions | url= | accessdate=2007-04-04]

Repairing permissions involves checking the permissions of a set of files and folders on a volume with Mac OS X 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 Installer package (.pkg) files in the Receipts folder in the local Library folder (/Library/Receipts) on the volume being checked. Whenever a user installs software that uses the Mac OS X Installer package format, a bill-of-materials file is created which can be consulted for future permission repair. [cite web | title=Apple - About Disk Utility's Repair Disk Permissions feature | url= | accessdate=2007-04-04]

Repairing permissions is a good first step in troubleshooting problems with Mac OS X; however, it is not a panacea. Files whose permissions have been incorrectly altered by an administrator, an administrator operating with root privileges, 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 Mac OS X. Some users periodically perform a permissions repair to prevent errors from developing; a practice considered useless (and even "voodoo") by several for versions of Mac OS X after Panther.


A permissions repair can be performed using Disk Utility (/Applications/Utilities/Disk by selecting a Mac OS X startup volume and clicking the Repair Disk Permissions in the First Aid section. A verification procedure, which will only check permissions, but not perform repairs, is also available. Both operations can be performed by using the diskutil command-line utility, which can be executed via local Terminal or remotely via SSH or the Send UNIX Command in Apple Remote Desktop:

diskutil repairPermissions /Volumes/


External links

* [ Repairing permissions: What you need to know] Macworld's Dan Frakes attempts to provide a thorough, balanced look at repairing permissions
* [ Repairing Permissions is Useless] Unsanity's Rosyna tries to educate mac users about repairing permissions.
* [ ‘Repair Permissions’ Is Not a Recommended Step When Applying System Updates] John Gruber questions the practise of repairing permissions.
* [ Seriously, ‘Repair Permissions’ Is Voodoo] Repairing permissions is declared to be voodoo.
* [ Troubleshooting permissions issues in Mac OS X] Apple document on troubleshooting permissions issues
* [ About Disk Utility's Repair Disk Permissions feature] Apple document on Disk Utility's repair disk permissions feature
* [ Care and Feeding of Jaguar: OS X Drive Maintenance] Arguments for repairing permissions regularly

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