I have a WD "my Passport" external HD that is currently formatted for a PC and I would like to format it to eXFAT. Every time I hit "erase" in disk util it just comes up with the error "couldn't unmount disk". Btw, I am running on Maverick. Can anyone help me with this please?

  • Do you see any processes in Activity Monitor that are higher than usual with the exFAT drive attached? I am curious if there is something like Spotlight or fsck trying to access the drive in the background thus you have issues ejecting/unmounting
    – Andrew U.
    Jan 9 '14 at 10:28

I had the same problem with the same drive. I finally got it to work by rebooting from the recovery partition and formatting it using the disk utility option.


It's proper for the operating system to not unmount a volume if there is, on the volume, an open file that can not be closed.

Recommended reading

The accepted answer to The volume can't be ejected because it's currently in use

  • note the comment about use of sudo

The Mac App Store page for WhatsOpen

Posts that mention What's Keeping Me?, e.g. https://apple.stackexchange.com/a/22268/8546

There's another comparable app but at the moment I can't recall its name.

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