Egg Freckles
Notes from my Newton

Tue Aug/20 Repair Disk Permissions





Prior to 10.6 you could use any version of Disk Utility on any version of Mac OS X to Repair Disk Permissions. It didn't matter because the disk permissions being inspected were always compared to the defaults stored in the local /Library/Receipts/ directory.

Starting Mac OS X v10.6 and later, Disk Utility doesn't even look in the /Library/Receipts/ directory when you Repair Disk Permissions. All it does is reset the Base Systems disk permissions back to the default as specified by version of Disk Utility you are using.1

  • Disk Utility can not repair permissions on any files in your Home Folder.2


Back in the days when Macs were capable of dual-booting into Mac OS 9 disk permissions were a big problem. Mac OS 9 didn't respect disk permissions. It treated every file as if you were root.


Since this was a relatively common occurrence and a huge support issue, Apple introduced the Repair Privileges Utility. Starting with Mac OS X 10.2 Jaguar the Repair Privileges Utility was combined with Disk Utility. Repair Disk Permissions offered early dual-booting Mac users a quick way to fix their systems and get Mac OS X working again. But now that Macs can't boot into Mac OS 9, why do we need to repair disk permissions?

The only time you need to run Repair Disk Permissions is if you changed a system-level permission you shouldn't have. Apple tries to educate users on changing permissions in knowledge base articles like this one, but warns incorrect commands may result in data loss and/or unusable system software, reduced system security and/or exposure of private data. It is best to leave system-level permissions alone. Sure the freak power outage, cosmic ray, or a runaway installer might mangle some permissions here or there, but those are rare occurrences.3

Leave Repair Disk Permissions for the people who need it most. Gullible people who don't know what they are doing, and still insist on Zapping their Mac's PRAM every third Sunday.
