Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Semi educated guess: / is the root volume of your internal disk, the "id -u" part, run the id command with the -u switch to get the id number of your account. And you do need the tick marks around the id part.

Try typing in at the Terminal just "diskutil resetuserpermissions" to see if you get a mini help reply: that might give some detail on what will happen.
 
Looks like there is a reason why Apple insist keeping homeFolder in the internal:
Code:
Last login: Fri Jul 26 19:14:16 on console
Mini2018:~ toke$ diskutil resetUserPermissions /Volumes/SSDhomeDir `id -u`
Ready to reset user permissions on disk6s1 SSDhomeDir
Started verify/repair permissions on disk6s1 SSDhomeDir
Error: -69838: Operation not supported for the macOS version on the targeted disk
 
If the external disk has a bootable system on it, try booting from it, then repairing with:
Code:
diskutil resetUserPermissions / `id -u`
It would only be necessary to run from the external for as long as it takes to do the repair.


If the OS (or user folder) isn't the same version as one is booted from, it's possible that diskutil is overly cautious about attempting repairs. This could be the reason for the error message, but that's just a guess, because we don't know which OS versions are being used here. That could be useful info to post.
 
  • Like
Reactions: toke lahti
If the external disk has a bootable system on it, try booting from it, then repairing with:
Code:
diskutil resetUserPermissions / `id -u`
It would only be necessary to run from the external for as long as it takes to do the repair.


If the OS (or user folder) isn't the same version as one is booted from, it's possible that diskutil is overly cautious about attempting repairs. This could be the reason for the error message, but that's just a guess, because we don't know which OS versions are being used here. That could be useful info to post.
It would be pretty nice, if Apple could allow repairing permissions just within one home folder.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.