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Short summary: User attempted to decrypt FileVault protection and got impatient; now can't get hard drive working at all. No file recovery needed (good backup, thank God), just need to get the hard drive to the point where I can actually work with it.

I have another system with a similar 1 TB drive, and used gpt to manually copy its partition scheme to the problem drive; it won't mount (from klanomoath's assistance to another user).

Also tried initializing the disk using Windows (NTFS); partially successful. It almost looks like FileVault somehow still has hold of the drive, even though everything, including the partition map, has been overwritten. Can't figure out how to just write enough of a format onto the drive so that Disk Utility has a place to start.

I just need to get this drive working, and don't care what data is destroyed. Can anyone tell me what I'm missing?

  • I'd use an OS X/macOS USB Installer to boot from and then use Disk Utility from it to wipe the existing partition structure of the Macintosh HD (actually the entire internal disk) and create a new partition structure. If need be I'd zap the first few megabytes of the disk using dd if Disk Utility is having issues deleting the existing partition structure. Then do a clean install of the OS. – user3439894 Sep 29 '16 at 14:50
  • Please add a link to my answer. Cloning another disk's GUID pt only works if the disks were identical (i.e partition tables and file systems). Adding a partition doesn't create a file system! – klanomath Sep 29 '16 at 14:54
  • This is the post I was looking at: apple.stackexchange.com/questions/175551/… – Mark Hartman Sep 30 '16 at 3:23
  • Tried doing what user3439894 suggested; no joy. – Mark Hartman Sep 30 '16 at 4:14
  • Also tried initializing the disk using Windows (NTFS); partially successful. It almost looks like FileVault somehow still has hold of the drive, even though everything, including the partition map, has been overwritten. Can't figure out how to just write enough of a format onto the drive so that Disk Utility has a place to start. – Mark Hartman Sep 30 '16 at 4:16
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I would highly recommend using Disk Maker X to create a bootable USB disk to reinstall OS X/macOS. Here's what you'll need:

  • Another Mac with access to the App Store (if the one you're trying to fix doesn't function enough to complete the following steps.
  • A USB drive/stick with a capacity of at least 8 GB. Also be sure it has absolutely no data on it, since it will be formatted.
  • An internet connection in order to download Disk Maker X.

First, download macOS Sierra on whichever Mac you're using by searching for it on the App Store, but don't install it! Next, download and install Disk Maker X on whichever Mac you're using. Then, open Disk Maker X and follow the steps listed. After that, make sure the Mac you're trying to fix is off. Plug in the USB Stick, then press Option and press the power key. Select the USB disk in the window that loads, follow the setup process, and you should be good to go! Let me know if you have any questions.

  • I did the dd erase (above) booted from a Sierra USB stick. I appreciate the suggestion, but doing that turns out not to affect the problem. – Mark Hartman Oct 1 '16 at 0:56
  • Hmmm... That's strange! – TDM Oct 1 '16 at 0:58
  • This whole THING is strange. :/ – Mark Hartman Oct 1 '16 at 0:58
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There's always the brute force method. This should clear anything and everything on the drive no matter what Filevault or anything else did to it.

  1. Connect the drive to a working machine. Mac or Linux, either will work here, but we'll continue as if on a mac. This should also work from inside the installer, as you can get to both Disk Utility and a terminal from there.

  2. Open Disk Utility, and note down which device the drive is using. On my personal system, this looks like:

    Screenshot of Disk Utility

    And the device name is "disk0" as shown on the bottom right. Make sure you have the main drive, not anything else under it. (That is, the drive itself, not any partitions). In my image, that's the "Crucial LGT.." not "Macintosh HD"

  3. Open Terminal.

  4. In your Terminal, become root with sudo su - and entering a password
  5. Make sure you've closed disk utility - we're about to confuse it.
  6. Run: dd if=/dev/zero of=/dev/DEVICENAME bs=1M

For the love of all things holy, make sure you get the device name right.

This will take a long time, but should throughly zero out the contents of the drive to allow it to be used with anything else.

Once this process finishes, reboot the machine. The drive should now be usable.

  • You don't have to zero the whole disk! Just zero the first 34 blocks(512) or 6 blocks(4096) – depending on the device block size – to delete the partition table. Additionally you may have to unmount the disk with diskutil umountDisk disk0 first to be able to dd .... – klanomath Sep 30 '16 at 21:37
  • Believe it or not, I tried that - from user3439894's suggestion above. However, I didn't use the "of=" flag, but the redirect std output syntax. I'll try it and report back. – Mark Hartman Sep 30 '16 at 21:52
  • Nope. Tried erasing 2000 1-MB blocks, and still getting the error message, "Wiping volume data to prevent future accidental probing failed." Now trying a full erase of the disk. – Mark Hartman Sep 30 '16 at 22:13
  • @Mikey T.K. Nope. Tried erasing the entire disk with dd, and still getting the above error message. However, the drive now shows up a "1 TB Uninitialized" in Disk Utility; not sure if that's significant. – Mark Hartman Sep 30 '16 at 23:35
  • @klanomath - for your info as well. – Mark Hartman Sep 30 '16 at 23:36

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