USB drive can't be unmounted because it's in use by process 563

KC_2020 wrote:

After updating to OS 15.1 USB drives cannot be formatted because they cannot be unmounted.

I get the error message: The volume "untitled" on disk4s1 couldn't be unmounted because it is in use by process 563 (mds_stores)

Couldn't unmount disk, : (-69888)

This happens with multiple known good USB drives.

From the Terminal.app copy and paste:

diskutil umount force 

notice the trailing blank space, now drag and drop your external HD icon directly onto the Terminal window to complete the path...

ex.

MacBook-Pro ~ % diskutil umount force /Volumes/Untitled

use the enter\return key to proceed, if it fails run it again.

A better option is to quit the Spotlight process using the PID you have. You may be able to do this using Activity monitor, or you can use the command line.

To be thorough, you can use the following command to identify which processes are using the mounted volume. Make sure to replace "<path-to-mounted-volume>" with the correct path, or better yet type the first part of the command making to leave at least one space after the "f ", the dragging & dropping the mounted volume from the Finder onto the open Terminal window so the system autofills the correct path for you.

sudo  lsof  <path-to-mounted-volume>

This will prompt you for your admin password. Nothing will appear on the screen as you type the password, so press the "Return" key to submit the password.

Assuming the mounted volume is called "MyVolume", the command would look like this:

sudo  lsof  /Volumes/MyVolume

Things get tricky when there are spaces in the path or volume name which is why dragging & dropping the volume from the Finder is best.

Once you have the Process ID(s) (aka PID), then you can use the following command to terminate those processes (replace "<PID>" with the actual Process ID found with the previous command):

sudo  kill  <PID>

For you at the time it would have been:

sudo  kill  563

After you do this to all the listed PIDs associated with the mounted volume, then you should be able to eject the drive normally (or you need to do that to each other volume on that drive).

If all else fails, then shutdown the computer so you can safely disconnect the drive.

I never like to force eject a drive that has any important data because it could corrupt the data and/or the file system.

KC_2020 wrote:

That worked.

Thanks for your feedback KC_2020, this will help others when then search for the same issue...