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The power went out and my external hard drive got pretty messed up. After several repair attempts I gave up and tried formatting the thing. I wasn't watching, but I believe Disk Utility hung on "unmounting disk" then crashed.

Now whenever I go back into it I see this:

enter image description here

(including Recovery Mode).

I can't do anything with it. The partition is locked.

How do I format this thing back to normal?

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Try gpart tool in linux – BlueBerry - Vignesh4303 Jul 29 '12 at 9:38
And if I don't own a linux computer? – ecnepsnai Jul 29 '12 at 20:10
up vote 1 down vote accepted

I was able to solve the problem by entering diskutil list in Terminal, finding the disk (my external drive was 500gb so I located the 500gb disk listed). And entering: diskutil eraseDisk HFS+ NewDrive disk1. It took a couple of seconds but now the external drive is back to normal! I did loose my backup but I'll just make another.

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