Repair permissions
Repairing disk permissions is a troubleshooting activity commonly associated with the Mac OS X operating system.
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 that should followed after any update.[3][4]
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>
References
- ^ "Apple - Developer - Security Overview: Permissions". Retrieved 2007-04-04.
- ^ "Apple - About Disk Utility's Repair Disk Permissions feature". Retrieved 2007-04-04.
- ^ "Daring Fireball - Seriously, Repair Permissions Is Voodoo". Retrieved 2009-03-13.
- ^ "Unsanity - Exercises in Futility Part 2: Repairing Permissions is Useless". Retrieved 2009-03-13.