Repair permissions on external hard drive

I have several external hard drives with different permissions on each of them. Some drives have me or system with read and write. Some drives have the group as staff or wheel as Read only or read and write. I’m not even sure what the right permissions for an external hard drive would be.

I already ran First Aid in Disk Utility and that didn’t reset the permissions.


You can easily change permissions per disk, and per user type within each disk, by choosing the drive, clicking Get Info, unlocking/authenticating then clicking settings to be changed.

What’s stored on the drives? Is it only data (as opposed to OS/Application files)? Does everything belong to you (or if not, do you want it to)?

Tried to do that but the interface doesn’t allow me to change.
Screen Shot 2020-05-12 at 15.34.18

It’s only data and all the data belongs to me.

I found out a couple more details:

  • I reformatted one partition and the default permissions had user=me and group=staff.
  • Time machine partitions permissions get changed to user=root and group=wheel
  • I have not tested yet if doing a bootable clone will change the permissions to (root, wheel) I’m guessing that it does change the permissions.

Next steps are to figure out how to reset the permissions back to (username, staff) on all the data partitions without reformatting. I’m not able to change them using “Get Info”

How comfortable are you with Unix commands? chown should work, unless Apple has done things that make it not compatible…

Did you follow the instructions in the link? (Did you first click the lock icon then authenticate with your password?)

You’re right, I didn’t fully read the instructions. I was able to set myself as the owner. I don’t see how to change the group from wheel to staff.

I’m comfortable enough with Unix commands.

“Wheel” is a special type of Unix group and I don’t know what you’d therefore want to change or why, as long as your drives are working properly. I’d google for technical info on these permissions if you’re idly interested, otherwise you might read a quick backgrounder here from someone with a similar question.

So it should be ok to leave the group as wheel? I was able to change the owner to me for the external drive.

drwxrwxr-x   8 macuser  staff   340B May 12 15:47 HDD01
drwxrwxr-x  14 root     wheel   544B Dec 19 02:46 HDD02
drwxrwxr-x  14 macuser  wheel   544B Dec 19 02:46 HDD03

HDD01 - Partition that I reformatted and looks ok
HDD02 - What I thought was weird
HDD03 - I was able to change the permission for the owner and I’ll leave as wheel for now.

I’m not sure why the owner and group got wonky.
For the pure data partitions, I wanted to rethink and consolidate data, so I repartitioned which fixed the permissions.
Thanks everybody.