disk utility volume could not be unmounted mac

Disk Utility Volume Could Not Be Unmounted on Mac: A Troubleshooting Guide

Are you struggling to unmount and erase your external hard drive in Disk Utility due to the 'volume could not be unmounted' error on your Mac? This issue can be frustrating, especially when you're trying to free up space or transfer data to a new device. In this article, we'll explore the common causes of this problem and provide step-by-step solutions to help you overcome it.

To troubleshoot the issue, let's start with the basics. I'm using a MacBook Air (M1, 2020) running Mac OS 11.3.1, and my external hard drive is a LaCie 'Rugged' 1 TB Firewire drive formatted as Mac OS Extended (Journaled). The problem occurs when I try to erase the volume, but the 'Force Eject' option works just fine.

One potential cause of the issue is that the volume is still in use by another process. In my case, the process 0 (kernel) is using the volume, which prevents me from unmounting it. To check if this is the case, you can try running First Aid on your external hard drive. If the volume is currently mounted, Disk Utility will not allow you to erase it.

To run First Aid, select the physical device instead of just the volume in Disk Utility. This should allow you to start the repair process without encountering any issues. Once First Aid has completed its scan and repairs, you may still encounter problems erasing the volume. In this case, try selecting the volume again and attempting to erase it.

If running First Aid on the physical device does not resolve the issue, there may be another problem preventing you from unmounting the volume. One possible cause is that the volume is still in use by a process or application. To identify which process is using the volume, you can try using the Activity Monitor app to check for any processes that are accessing the drive.

In my case, I found that trying to delete files on the external hard drive using Finder resulted in an 'unexpected error' (code -50). When attempting to remove files using the Terminal and the `rm` command, I received an 'Invalid argument' message. This suggests that there may be a problem with the file system or permissions on the volume.

To resolve this issue, you can try restarting your Mac and then attempting to erase the volume again. If this does not work, you may need to try more advanced troubleshooting techniques, such as using the `fsck` command in the Terminal to check and repair any file system errors.

In conclusion, the 'volume could not be unmounted' error in Disk Utility can be caused by a variety of factors, including the volume being in use by another process or application. By running First Aid on the physical device, checking for processes that are accessing the drive, and attempting to erase the volume again after restarting your Mac, you should be able to overcome this issue and successfully erase your external hard drive.

Disk utility volume could not be unmounted mac