- Repair permissions
Repairing disk permissions is a
troubleshooting activity commonly associated with theMac OS X operating system .Overview
The
BSD layer in Mac OS X (and Darwin) is responsible for filesystem security, including the management of theUnix (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=http://developer.apple.com/documentation/Security/Conceptual/Security_Overview/Concepts/chapter_3_section_9.html | 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=http://docs.info.apple.com/article.html?artnum=25751 | 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.
Usage
A permissions repair can be performed using Disk Utility (/Applications/Utilities/Disk Utility.app) 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/References
External links
* [http://www.macworld.com/2006/08/secrets/repairpermissions/ Repairing permissions: What you need to know]
Macworld 's Dan Frakes attempts to provide a thorough, balanced look at repairing permissions
* [http://www.unsanity.org/archives/000410.php Repairing Permissions is Useless]Unsanity 's Rosyna tries to educate mac users about repairing permissions.
* [http://daringfireball.net/2006/04/repair_permissions ‘Repair Permissions’ Is Not a Recommended Step When Applying System Updates]John Gruber questions the practise of repairing permissions.
* [http://daringfireball.net/2006/04/repair_permissions_voodoo Seriously, ‘Repair Permissions’ Is Voodoo] Repairing permissions is declared to be voodoo.
* [http://docs.info.apple.com/article.html?artnum=106712 Troubleshooting permissions issues in Mac OS X] Apple document on troubleshooting permissions issues
* [http://docs.info.apple.com/article.html?artnum=25751 About Disk Utility's Repair Disk Permissions feature] Apple document on Disk Utility's repair disk permissions feature
* [http://www.lafcpug.org/care_feeding_jag_print.html Care and Feeding of Jaguar: OS X Drive Maintenance] Arguments for repairing permissions regularly
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