Victoria Herring
Level 2 (297 points)
Mac OS X

Q: Using Disk Utility to Erase Disk-won't unmount

I have a MacPro and 4 drives inside it, one of which I need/want to erase.  I have backed it  up and using DU tried to erase it = by both highlighting the drive identifier and the name - in both cases, whether I try to erase disk or set it to erase to one partition, I get a message saying it can't do it because it can't unmount the disk.

 

I backed up my startup drive to this drive so I could wipe and reinstall OSX on my new SU drive but now I can't delete items off the backup drive [the one I want to erase] because the message says I can't delete backup items.  And I can't erase the drive to get a brand new drive to work with.

 

I don't need the old SU material on this drive, it was just a way to be sure I had it before using Migration Asst to reinstall the SU on the new SU drive = I used SuperDuper to clone the old SU onto this drive - then I used Migration Asst to move the stuff back to the new startup drive = but now I want to EITHER get rid of the system files and apps [no need for those = I don't min

Mac OS X (10.7.4), iPad and iPhone4

Posted on Jul 18, 2012 11:16 AM

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Victoria Herring

Q: Using Disk Utility to Erase Disk-won't unmount

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  • by elooPS,

    elooPS elooPS Sep 18, 2015 1:12 PM in response to Coluch
    Level 1 (0 points)
    Sep 18, 2015 1:12 PM in response to Coluch

    Option key heaven... thanks Coluch!! This worked first time for me, a total mac newbie!

  • by lylialikeapple,

    lylialikeapple lylialikeapple Nov 2, 2015 1:50 PM in response to Holmes321
    Level 1 (0 points)
    Nov 2, 2015 1:50 PM in response to Holmes321

    Huge thanks to Holmes321 and Dana 刀!!!!

     

    My laptop is early 2008 MBP (runs 10.10.5) , and I use LaCie 2TB external hard drive as my time machine. I only do back up once a month. But 3 days ago, when I wanted to do back up, I found out there is no icon of my time machine disk on the screen, but I could see it in Disk utilities.

     

    After I read some discussions here, I tried everything here mentioned. But for the people like me, who have a very little knowledge about computer, some words which people said here, I am difficult to understand and follow.  (I did ask a friend to help me to understand how to follow these steps).

     

    Finally, after all of tryings failed, (really I did try everything here the people mentioned), which always give me the same info "couldn't unmount disk". I found out "Holmes321" who wrote every step very clear. I followed what he said, wow, it finally worked! Now I have reformatted my external drive!

    Massive thanks!

  • by someotherandomguy,

    someotherandomguy someotherandomguy Jan 11, 2016 12:48 AM in response to Linc Davis
    Level 1 (0 points)
    Jan 11, 2016 12:48 AM in response to Linc Davis

    Every time I have a problem with a mac, you always have the best answers. it's like the 5th time you saved my ***. I'm not even sure if you're real or not. But thank you.

  • by madmu5icjunky,

    madmu5icjunky madmu5icjunky Jan 12, 2016 8:05 PM in response to eplt@odw
    Level 1 (0 points)
    Jan 12, 2016 8:05 PM in response to eplt@odw

    Thank you very much!  I tried killing spotlight, but that didn't do anything.  Following your instructions is what did it.  I would've never known how to force unmount a disk through Terminal otherwise!

  • by Eirig,

    Eirig Eirig Mar 13, 2016 10:16 AM in response to Victoria Herring
    Level 1 (0 points)
    Mar 13, 2016 10:16 AM in response to Victoria Herring

    HI to all, i have the sampe problem here. It's so frustated. My basic is not an it, i'm just a normal user doesnt understantd any programing language. Can anybody please help to guide me?

     

    ps : i already tried what you guys tell in here, go to terminal.. But i dont get it, which one is process number (sorry this is not my expertise) i'm just a noob

     

    thank youu

     

    E R

  • by Desny,

    Desny Desny May 2, 2016 11:25 PM in response to eplt@odw
    Level 1 (4 points)
    May 2, 2016 11:25 PM in response to eplt@odw

    This just saved both my drive and my sanity. Thank you SO much!

  • by baimhanifkamil,

    baimhanifkamil baimhanifkamil Jul 13, 2016 10:49 AM in response to Victoria Herring
    Level 1 (8 points)
    Jul 13, 2016 10:49 AM in response to Victoria Herring

    I have found the easiest solution ever!!!!!

     

    1) Eject disk from desktop

    2) Open Disk Utility

    3) Erase!

     

    Ps: I've tried all the top comments before but didn't worked.

  • by DEDASS,

    DEDASS DEDASS Aug 10, 2016 3:47 AM in response to Holmes321
    Level 1 (4 points)
    Aug 10, 2016 3:47 AM in response to Holmes321

    Thanks.... but I doesn't wish to work for me. I'm in Target Mode, my other macs sees the affect drive. I have Terminal open drop in the lines, head back to DU, hit erase and I get the same "Couldn't unmount disk" issue. :-(

  • by DEDASS,

    DEDASS DEDASS Aug 10, 2016 4:02 AM in response to eplt@odw
    Level 1 (4 points)
    Aug 10, 2016 4:02 AM in response to eplt@odw

    sadly I received this back 'Forced unmount of disk2 failed: at least one volume could not be unmounted'. Any advice on what to do next would be great appreciated.

  • by vic_france,

    vic_france vic_france Sep 5, 2016 10:33 AM in response to eplt@odw
    Level 1 (4 points)
    Sep 5, 2016 10:33 AM in response to eplt@odw

    Thank you .. those were the terminal commands I was looking for (similar "unable to unmount partition" problem (not Spotlight-related though). Once the disk was unmounted, I was able to use Disk Utility to Repair the disk (reported as ok though ), and, from there, Disk Warrior to rebuild the directory (again, nothing serious found, but, what the heck.. the combination of all that worked for me )

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