BATCHMOD PERMISSIONS SOFTWARE

What the support note does not say is that software might change those permissions for you. The note refers to the user changing those permissions, but in my experience few users are ever likely to do that deliberately, and it is most unlikely to be accidental.

The question that Apple’s support note does not consider is how the permissions in, say, ~/Library might get changed. Apple has recognised that changing their permissions can result in a wide range of problems, few of which clearly point to it being a permissions problem. There are still plenty of unprotected folders and files, including many of those in /Library, third-party apps in /Applications, and of course everything in your Home folder, particularly in ~/Library. So that makes traditional repair of permissions superfluous, and it could only have been performed in Recovery mode in any case. No app, no matter how badly behaved, can change permissions or anything else in those protected files. The only ways that they can get changed involve special Apple-signed installers, or Recovery mode. Since Apple introduced its System Integrity Protection (SIP) in El Capitan, all macOS system files – including now all the bundled apps too – are protected from intentional and inadvertent tampering. With details buried away in one of Apple’s lesser-known support notes, this also relies on an undocumented Terminal command. Amazingly, Apple is recommending it as a solution again, only this time it’s not the permissions in macOS, but those of your Home folder. We used to do it often, and it could fix the most intransigent of problems at times: repairing permissions.

Batchmod permissions