Don't Have Permission to Erase & First Aid Check the External Drive on Mac

macos tips
1

My new SanDisk external drive is formatted in exFAT. I found I couldn’t access files on it on my MacBook Air.

So I went to Disk Utility to check it, but failed.

Tried erasing the drive, failed either.

Only got “The operation can’t be completed because you don’t have the necessary permission.”

Went to Get Info > Sharing & Permission, it shows " You have custom access."
What should I do?

2

I suggest you reconnect the drive to your Mac. This can verify if macOS failed to recognize your SanDisk drive properly before.

If you still can’t do any operation on the exFAT SanDisk drive on your Mac, try using a Windows PC to reformat it.

“You have custom access” means the permission settings on that drive don’t match any of the standard combinations Finder can summarize.

Although exFAT is supported by both Mac and PC, there are slight differences in technical differences and caveats when formatting a drive to exFAT on the two OS.

That may be the reason why the exFAT shows “You have custom access” on Mac.

Remember, choose GPT as the partition table. GPT is better for drives working on modern Macs & Windows PCs.

3

Got it. You can’t change permissions on the external drive on your Mac. This issue can be triggered by system errors, glitches between your Mac and the external drive, a corrupted disk partition table, etc.

Are you sure you can’t erase the external drive? exFAT is compatible with macOS. Usually, when an external drive is inaccessible on a Mac, you can recover data from it and then erase it.

Given that you can’t access the external drive, I suggest you recover files from the corrupted drive with data recovery software first, like iBoysoft Data Recovery for Mac.

This tool can restore files from inaccessible, unreadable, and corrupted external hard drives.

Simply download iBoysoft Data Recovery for Mac and install and open it.
Choose the problematic exFAT external drive and click Search for Lost Data.
After scanning, check, preview, and choose your desired files, and click Recover to save them to a different destination.

After that, try using Terminal to erase your exFAT external hard drive.

Open Terminal.
Enter this command:

diskutil list

Find your SanDisk exFAT drive (for example, /dev/disk3) from the list.
Enter the following command to erase it.

diskutil eraseDisk APFS SANDISK GPT /dev/disk3