Couldn't unmount disk

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Level 1

8 points

Couldn't unmount disk

I've been having issues with my computer constantly restarting after updating to Yosemite, so I'm trying to restore my computer back to factory settings (snow leopard) and going from there. I'm having trouble erasing the Mac hard drive though.

I have the original Mac installation disk in the computer, restarted the computer, and got into the Disk Utility by holding command + R, while it was restarting. When I click on the Mac HD (which is named "320.07 GB Hitachi HTS545032B9SA02 Media"), and then went to the Erase tab, and clicked "Erase..." and I get the error:

"Disk Erase Failed

Disk Erase failed with the error:

Couldn't unmount disk."

When I go into the Partition tab, I have one partition, and it's 275.44GB out of my available 320.07. When I try to expand the partition to fill in that extra space, and click "Apply", I get the error:

"Partition failed

Partition failed with the error:

Couldn't unmount disk."

I've went into Terminal, and typed: diskutil list

I then typed: diskutil unmountDisk force disk0 Followed by error:

"Forced unmount of disk0 failed: at least one volume could not be unmounted."

I need to get this hd unmounted so I can erase the hard drive, and I've run out of options. This is going to be a tough one, so if anyone could help me out, I would appreciate it so much. Thank you

MacBook Pro (15-inch Mid 2010), iOS 8.1.2, Photo Booth

Posted on Jun 20, 2015 9:42 PM

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Answer 1

YooZurNaim Author

Level 1

8 points

Jun 21, 2015 12:03 AM in response to YooZurNaim

i finally got it working, in case someone else runs into this issue, these are the steps I took. I can't guarantee this will work for you, but this is what worked for me:

in the picture above, for some reason, there were 15 different disks. I tried to unmount disk0 by typing: diskutil unmountDisk force disk0

it said the partition could not be unmounted

i then unmounted disks 1 at a time, starting with disk3, and after each disk I unnounted, I then tried to unmount disk0 again. I typed "diskutil unmountDisk force disk3", and it unmounted

i tried to force unmount disk0, and it again said it couldn't be unmounted

i forced disk4 to unmount "diskutil unmountDisk force disk4" and it unmounted

i tried to unmount disk0 again, and it successfully unmounted

now, I did that a few times successfully, but when I would close out of Terminal to go back into Disk Utility, I would get the spinning rainbow wheel, and would have to restart my computer and start over again, so this time, after unmounting disk0 successfully, I tried to erase the hard drive through Terminal by typing "diskutil eraseDisk JHSF+ Mac /dev/disk0" (WARNING! That command WILL erase EVERYTHING!)

it got to 20% removing disk0, and I clicked something, and got the rainbow wheel and froze up, and unfortunately had to restart the computer... I turned it back on, and where the apple logo usually shows up at boot up, it showed a folder icon with a question mark inside of it. Eventually, it went to an apple, and took about 5-10 minutes to reboot. I thought I had completely bricked my computer... It eventually booted up to the snow leopard welcome installation page, and I went through the installation, and snow leopard successfully reinstalled, and everything is working again! I used to do technical support for 3 years on computers (mostly Mac), and this was pretty extensive even for me, so if for even a second you don't feel comfortable doing any of this, DONT DO IT! It worked for me though

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Answer 2

YooZurNaim Author

Level 1

8 points

Jun 20, 2015 10:13 PM in response to YooZurNaim

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