Repairing disk permissions is a troubleshooting activity commonly associated with the

macOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

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

Overview

The

BSD The Berkeley Software Distribution (BSD), also known as Berkeley Unix or BSD Unix, is a discontinued Unix operating system developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley, beginni ...

layer in macOS is responsible for file-system security, including the management of the

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

(

POSIX The Portable Operating System Interface (POSIX; ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with comm ...

) permissions 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 macOS 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 directory () on the volume being checked. Whenever a user installs software that uses the macOS Installer

package format Package format is a type of archive containing computer programs and additional metadata needed by package managers; an instance of this type of archive is called a package. While the archive file format itself may be unchanged, package formats c ...

, 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 macOS. Repairing permissions can become necessary, but has become increasingly less so for versions after Panther (10.3). In

OS X El Capitan OS X El Capitan ( ) () is the twelfth major release of macOS (named OS X at the time of El Capitan's release), Apple Inc.'s desktop and server operating system for Macintosh. It focuses mainly on performance, stability, and security. Followi ...

, Apple introduced a security feature called System Integrity Protection. With it enabled, root privileges are no longer able to change system files and folders, including their permissions. Permissions repairs are instead performed automatically upon system installs and updates. To that end,

Disk Utility A disk utility is a utility software, utility program that allows a user to perform various functions on a computer disk, such as disk partitioning and logical volume management, as well as multiple smaller tasks such as changing drive letters an ...

as well as the corresponding command-line utility lost the ability to repair permissions.

Usage

In systems prior to OS X El Capitan, a permissions repair can be performed by selecting a startup volume and clicking the "Repair Disk Permissions" button in the "First Aid" section of Disk Utility. The operation can also be performed by using the command-line utility. In El Capitan, the user can instead use two command-line utilities: to repair particular packages or to repair a standard set of system packages. In both cases, the user has to disable System Integrity Protection to change permissions of system files and directories. In macOS Sierra, is not available. Permissions can also be repaired using third-party utilities such as The Apotek's AppleJack or Prosoft Engineering's Drive Genius.

References

{{reflist Apple Inc. software MacOS