Time Machine USB Drive Stopped Working after Upgrading to macOS Tahoe

macos tips
1

After upgrading to macOS Tahoe, a Time Machine USB drive stopped working.
First Aid reports “permission denied” and file system errors.
There’s a folder named “.inProgress” on the drive, and it can’t be reformatted or deleted. Although the user has Read & Write permissions, macOS says “You can only read,” suggesting a permissions issue preventing Time Machine from functioning.

2

I had the same thing happen after upgrading to macOS 26.
Time Machine somehow locked the entire volume because of that “.inProgress” folder.
Normal Disk Utility won’t access it either.
What fixed it for me was erasing the drive in macOS Recovery Mode.

You can use a data recovery tool to restore files from the drive before erasing it.
I have used iBoysoft Data Recovery for Mac to get files off the unworkable USB drive.

Download iBoysoft Data Recovery for Mac, and then install and open it.
Select the USB drive and click Search for Lost Data.
After scanning, check the results, preview and select the desired files, and click Recover to save them to a different destination.

After that, enter macOS Recovery Mode to erase the drive:

Open Disk Utility there.
Select the USB drive (not just the volume under it), and click Erase.

If it still fails, open Terminal from the Utilities menu and run the command below to list the volumes on your Mac.

diskutil list

Enter the following command to wipe the drive.

diskutil eraseDisk APFS TMDRIVE /dev/disk2

(Replace /dev/disk2 with your actual drive identifier from diskutil list).

3

That “.inProgress” folder is a broken backup session, and it can block Time Machine from accessing the disk. I’d suggest you try these tricks:

  1. Turn off Time Machine in System Settings.
  2. Eject and unplug the USB drive.
  3. Reboot your Mac.

Plug the drive back in and see if you can erase it using Disk Utility > View > Show All Devices, then select the parent drive (not the volume on the drive) before erasing.

If that still fails, connect it to another Mac (or even a PC) and format it there. Once it’s reformatted, reconnect and set it up fresh for Time Machine.