Repair permissions
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Repairing disk permissions is a troubleshooting activity commonly associated with the Mac OS X operating system.
[edit] Overview
The BSD layer in Mac OS X (and Darwin) is responsible for file-system 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.[1]
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.[2]
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 for versions of Mac OS X after Panther.[3][4]
[edit] 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/<disk name>
[edit] References
- ^ "Apple - Developer - Security Overview: Permissions". http://developer.apple.com/documentation/Security/Conceptual/Security_Overview/Concepts/chapter_3_section_9.html. Retrieved on 2007-04-04.
- ^ "Apple - About Disk Utility's Repair Disk Permissions feature". http://docs.info.apple.com/article.html?artnum=25751. Retrieved on 2007-04-04.
- ^ "Daring Fireball - Seriously, Repair Permissions Is Voodoo". http://daringfireball.net/2006/04/repair_permissions_voodoo. Retrieved on 2009-03-13.
- ^ "Unsanity - Exercises in Futility Part 2: Repairing Permissions is Useless". http://www.unsanity.org/archives/000410.php. Retrieved on 2009-03-13.
