studio_

Q: Disk Erase failed with the error:  Couldn’t unmount disk. Running Mavericks

I am running Mavericks OX 10.9.1 and am trying to erase an external hard drive that has been partioned. I keep coming up with the error message "Disk Erase failed with the error:  Couldn’t unmount disk." Any suggestions?

iMac, OS X Mavericks (10.9.1)

Posted on Jan 21, 2014 1:45 PM

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Q: Disk Erase failed with the error:  Couldn’t unmount disk. Running Mavericks

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  • by Kappy,

    Kappy Kappy Jan 21, 2014 1:48 PM in response to studio_
    Level 10 (271,174 points)
    Desktops
    Jan 21, 2014 1:48 PM in response to studio_

    Eject the drive, wait a minute or two, then reconnect it. Try again.

  • by studio_,

    studio_ studio_ Jan 21, 2014 2:11 PM in response to Kappy
    Level 1 (2 points)
    Jan 21, 2014 2:11 PM in response to Kappy

    Hey Kappy, thanks for your reply! It was a no go though

  • by Kappy,

    Kappy Kappy Jan 21, 2014 2:17 PM in response to studio_
    Level 10 (271,174 points)
    Desktops
    Jan 21, 2014 2:17 PM in response to studio_

    There must be something on the drive that has a connection to the internal drive, I think. Try booting from the Recovery HD:

     

    Boot to the Recovery HD:

     

    Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the arrow button below the icon.

     

    Select Disk Utility from the list and click on the Continue button. See if this lets you erase the drive.

  • by Dr.Mac.,

    Dr.Mac. Dr.Mac. Jan 21, 2014 2:26 PM in response to studio_
    Level 3 (636 points)
    Jan 21, 2014 2:26 PM in response to studio_

    To list all the drives and their accompanying partitions from the Terminal, type the following command:

     

    diskutil list

     

    This will give you a listing out the drives, their volume names, the size of the drive and partitions, their partition types, and their identifier location.   Paste the disk drives listing into a reply to this message.

     

     

     


  • by Kappy,

    Kappy Kappy Jan 21, 2014 2:26 PM in response to Dr.Mac.
    Level 10 (271,174 points)
    Desktops
    Jan 21, 2014 2:26 PM in response to Dr.Mac.

    We aren't there, yet. That will be part of the next thing to try - force unmounting using diskutil.

  • by studio_,

    studio_ studio_ Jan 21, 2014 2:58 PM in response to Kappy
    Level 1 (2 points)
    Jan 21, 2014 2:58 PM in response to Kappy

    Booting to a Recovery HD wasn't an option... the external HD I am trying to erase is for my Time Machine BU. Does that make a difference? I currently do not have a Time Machine BU.

  • by Kappy,

    Kappy Kappy Jan 21, 2014 3:04 PM in response to studio_
    Level 10 (271,174 points)
    Desktops
    Jan 21, 2014 3:04 PM in response to studio_

    Why are you unable to boot from a Recovery HD? When you tried to eject the drive, were you able to do so? You said, "no go," but I'm not sure what that meant.

  • by Dr.Mac.,

    Dr.Mac. Dr.Mac. Jan 21, 2014 3:16 PM in response to studio_
    Level 3 (636 points)
    Jan 21, 2014 3:16 PM in response to studio_

    The external HD is for my Time Machine BU. Does that make a difference?  No difference.

     

    Unable to use  Recovery HD:  Probably the  Recovery HD is damaged.


     

    Open the Terminal, and type the following command:


    diskutil list

     

    and paste the output into a reply to this message.

  • by studio_,

    studio_ studio_ Jan 21, 2014 3:17 PM in response to Kappy
    Level 1 (2 points)
    Jan 21, 2014 3:17 PM in response to Kappy

    sorry, I should clarify. I was able to eject the external HD, but after waiting a few minutes and reconnecting it, I was still not able to erase the external hard drive.

     

    I also tried to erase the drive after a simple restart of the computer. That did not work.

     

    When I restarted the computer with command + r at the chime, the menu came up, but did not have the option of "Recovery HD".

     

    I can try again and tell you what my options are if that will help...

  • by studio_,

    studio_ studio_ Jan 21, 2014 3:21 PM in response to Dr.Mac.
    Level 1 (2 points)
    Jan 21, 2014 3:21 PM in response to Dr.Mac.

    #:                       TYPE NAME                    SIZE       IDENTIFIER

       0:      GUID_partition_scheme                        *2.0 TB     disk0

       1:                        EFI EFI                     209.7 MB   disk0s1

       2:                  Apple_HFS OSX                     869.3 GB   disk0s2

       3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

       4:                  Apple_HFS TAGP                    1.1 TB     disk0s4

       5:                  Apple_HFS Scratch                 49.8 GB    disk0s5

    /dev/disk1

       #:                       TYPE NAME                    SIZE       IDENTIFIER

       0:      GUID_partition_scheme                        *1.0 TB     disk1

       1:                        EFI EFI                     209.7 MB   disk1s1

       2:                  Apple_HFS Production iMac Clone   250.0 GB   disk1s2

       3:                  Apple_HFS Production iMac Time... 749.7 GB   disk1s3

  • by Kappy,Helpful

    Kappy Kappy Jan 21, 2014 3:21 PM in response to studio_
    Level 10 (271,174 points)
    Desktops
    Jan 21, 2014 3:21 PM in response to studio_

    Here's a suggestion you might try:

     

    It appeared that the external drive would not unmount because some activity was using it.  fsck_hfs process was working away as shown by activity monitor.  It seems that Spotlight was struggling with a the failed drive and would not let it go so the unmount and erase could not occur.

    This was solved by disabling Spotlight (terminal: sudo mdutil -a -i off) temporarily.  After disabling Spotlight, Disk Utility performed its job and my corrupted drive was restored to use.

     

    (Spotlight is turned back on with: sudo mdutil -a -i on)

     

    This is from a 2012 discussion re: this problem. It helped some users, so give it a go.

  • by Dr.Mac.,

    Dr.Mac. Dr.Mac. Jan 21, 2014 3:27 PM in response to studio_
    Level 3 (636 points)
    Jan 21, 2014 3:27 PM in response to studio_

    Open the Terminal, and type the following command:


    diskutil unmountDisk force disk1

     

     


  • by Kappy,Helpful

    Kappy Kappy Jan 21, 2014 3:30 PM in response to Dr.Mac.
    Level 10 (271,174 points)
    Desktops
    Jan 21, 2014 3:30 PM in response to Dr.Mac.

    I think he needs to use sudo:

     

         sudo diskutil unmountDisk force disk1

     

    Press RETURN. Enter your admin password when prompted. It will not echo back to the screen. Press RETURN again.

  • by studio_,

    studio_ studio_ Jan 21, 2014 3:31 PM in response to Kappy
    Level 1 (2 points)
    Jan 21, 2014 3:31 PM in response to Kappy

    Thank you!! This worked. I also turned off Time Machine, as I had set this drive to be the BU for Time Machine (but because of the partion, did not have enough free space). I suppose a better techy (than myself) would have seen that right away, but with your post Kappy, I was able to fix it! Thanks so much Kappy and Dr. Mac!

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