Repairing disk permissions is a troubleshooting

Troubleshooting

Troubleshooting is a form of problem solving, often applied to repair failed products or processes. It is a logical, systematic search for the source of a problem so that it can be solved, and so the product or process can be made operational again. Troubleshooting is needed to develop and...

 activity commonly associated with the Mac OS X

Mac OS X

Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

 operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

. The efficacy of repairing permissions to troubleshoot application errors has been debated.

Overview

The BSD layer in Mac OS X (and Darwin

Darwin (operating system)

Darwin is an open source POSIX-compliant computer operating system released by Apple Inc. in 2000. It is composed of code developed by Apple, as well as code derived from NeXTSTEP, BSD, and other free software projects....

) is responsible for file-system security, including the management of the Unix

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 (POSIX

POSIX

POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...

) permissions

File system permissions

Most current file systems have methods of administering permissions or access rights to specific users and groups of users. These systems control the ability of the users to view or make changes to the contents of the filesystem....

 model. Applications depend on the correct assignment and interpretation of permissions in order to function properly.

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.

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. Repairing permissions can become necessary, but has become increasingly less so for versions of Mac OS X after Panther (10.3).

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

Secure Shell

Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...

 or the Send UNIX Command in Apple Remote Desktop

Apple Remote Desktop

Apple Remote Desktop is a Macintosh application produced by Apple Inc., first released on March 14, 2002, that replaced a similar product called Apple Network Assistant...

:

diskutil repairPermissions /Volumes/

Permissions can also be repaired using third part utilities, such as AppleJack

AppleJack

AppleJack is a command-line interface for Mac OS X that provides a simplified user interface for single user mode system repairs. It allows for permission repair, disk repair, cache cleaning, validation of preference- and property list files, and removal of swap files on a boot drive, without...

 or Prosoft Engineering

Prosoft Engineering

Prosoft Engineering Inc. is software developer based in Livermore, California, USA.-About Prosoft:Founded in 1985, Prosoft Engineering Inc. is a software manufacturer developing data recovery software for the Mac and PC. The company’s Data recovery software is used by data recovery services, law...

's Drive Genius.