mac - I want to reformat my external hard disk but disk utility said it could not be unmounted

08
2014-07
  • Faith

    Hi I wanted to reformat my HP 500GB hard disk to MS DOS (FAT) by using Disk Utility but Disk Utility kept saying that the hard disk cannot be unmounted. I tried googling it but nothing seems to answer my question. I'm not trying to reformat the hard disk in my Mac but my external hard disk!

    I usually format my hard disks to clear the documents I no longer need. And I'll change it to ExFat but currently, whenever I plug in my hard disk on Windows, the whole system just hangs there.

    Can someone help??

    • Answers
  • Alex

    You can't have any files that are located in the external hard drive opened when trying to format it, nor any program installed on it running. Try unplugging and then plugging it, then immediately formatting it.

    Assuming you're on OSX, if you're still unable to unmount it, you can try forcing an unmount by issuing the follow command:

    sudo umount -f /Volumes/External_HD_Name

    Alternatively, try forcing an unmount with disk utility:

    sudo diskutil umount force /Volumes/External_HD_Name

    Replacing External_HD_Name with the your disk's name.

    Alternativly you can prevent a device from being automatically mounted following this tutorial. You can also burn GParted to a CD, boot it and try to format your external HD from it.


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    dvd - Input/output error using Mac Disk Utility?
  • CT.

    I began trying to backup my dvd collection to an external hard drive. I do this my making disk images(.iso) from the dvds. To do this I use disk utility > new image > save as dvd/cd master. Started with some Battlestar Galactica. First 6 disks of season 1 went fine. Next 3 disks of season 2 went fine. First disk of season 2.5 I get an input/output error about 75% through the process. Any ideas?


    • Related Answers
  • calvin123

    I think the issue is with your disk. If you have access to a spin doctor I would suggest that.

    Since your trying to get it as an iso, MacTheRipper and Handbrake will not do this. You could try http://www.xilisoft.com/dvd-copy-mac.html .

    You could also dd from the comand line. But this may be what disk utility already uses to create cd/dvd master copies. Just google this for syntax.

  • jweede

    This could be a problem with the drive, or (more likely) a problem with the DVD. Perhaps there's a scratch on it, or maybe just a smudge. It's tough to say.

    If you copy the files directly, you can still play it with VLC.

    Also Disk Utility is not your only choice for backing up DVDs. I will point to MactheRipper or Handbrake for other options.