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I'm unable to eject USB drives. When I try, I get this error:

The disk "Untitled" wasn't ejected because one or more programs may be using it.

To eject the disk immediately, click the Force Eject button.

Additionally, when I use Disk Utility to erase a USB drive I get this error:

Disk Erase failed with the error:

Couldn't unmount disk.

This happens on my account and my wife's account. I can partition USB drives, but I can't erase or eject them.

Any ideas on how to resolve this?

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3 Answers 3

up vote 2 down vote accepted

When you have this kind of error, typically it occurs because the device is mounted and there is something accessing the information on the mounted disk. Whatever is causing you to be unable to eject the disk is the same reason the disk utility can't unmount the drive to erase it.

Likely culprits for things still accessing your files include applications like Preview or possibly Dropbox if you use it to import the information. If the USB drives include songs, iTunes could possibly be accessing the information as well. You want to make sure that all of these types of apps are closed when you go to dismount.

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I had the same problem, found a hint for solution here: http://www.snowcrash.eu/disk-wasnt-ejected-because-one-or-more-programs-may-be-using-it/.

In my case the culprit was a small non-archived program file (an old crack from Mac OS 8 days) which somehow stayed open by an unknown process in the system. I just force-deleted it and the problem’s gone, now the disk ejects normally.

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You can use lsof to list open files:

sudo lsof|grep /Volumes/Volume\ name

If you run lsof without sudo, it doesn't include processes owned by other users.

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