couldn't unmount disk

trying to do time machine backup. connected and selected external hard disc drive. I get the message "there was an error preparing "extreme SSD". "couldn't unmount disk". what does this mean and what do I do?

MacBook Pro 16″, macOS 12.6

Posted on Jul 5, 2023 6:20 PM

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1 reply

leroydouglas

Level 10

205,788 points

Jul 6, 2023 11:44 AM in response to lilayda

lilayda wrote:

trying to do time machine backup. connected and selected external hard disc drive. I get the message "there was an error preparing "extreme SSD". "couldn't unmount disk". what does this mean and what do I do?

From the Terminal.app you can umount, and try again

copy and paste:

diskutil umount

notice the trailing blank space, drag your external from the Desktop onto the Terminal window to complete the path, proceed using the enter\return key...

ex.

MacBook-Pro ~ % diskutil umount /Volumes/Install\ macOS\ Ventura

Volume Install macOS Ventura on disk2s2 unmounted

MacBook-Pro ~ %

ref:

Back up your Mac Back up your Mac with Time Machine - Apple Support

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