I've installed El Capitan Developer Preview . Installation crashed at about 75% and then i could only boot in safe mode.

I wiped all the hard drive to reinstall Yosemite but it only displays 10.11 as an installation option. However, installing it won't work either. It says this disk is locked (the one I just wiped).

Now I can not even unmount it again.

I tried in the Terminal to erase it, won't work either.

Anyone else having these issues, or has any clue how I can solve the problem (install Yosemite)?

  • also see apple.stackexchange.com/questions/135677/…
    – nohillside
    Jun 13, 2015 at 7:42
  • Thanks for replying. This does not help though since I have already wiped all my data and now my drive is locked thus i can not install something else on it. I belive the only option is to somehow unlock it through the terminal, but i do not know the commands. Also the current terminal doesnt know about sudo and i have the el-capitan version of recovery mode. Sorry for typos. I am on the phone.
    – mironAlex
    Jun 13, 2015 at 8:01

2 Answers 2


If you're looking for a Terminal solution, you can try this:

diskutil eraseVolume free %noformat% disk0s2


diskutil eraseDisk free %noformat% GPT disk0

In this case, disk0 should be changed to match whatever your actual device node is. It will depend on whether you're using a USB stick to boot into recovery – in which case it's probably disk1 – or if you're actually booting off of the disk you're trying to erase.

And an important disclaimer: If you blow away your disk, you will not be able to boot into the onboard recovery mode. In fact, you probably aren't going to be able to do this without booting off of USB. I hope you have a recovery stick somewhere, or another computer from which you can make one.

It should go without saying that you will lose data if you run either one of these commands successfully.

  • 1
    Whilst you won't be able to boot into the "onboard recovery mode", Internet Recovery should still work.
    – grg
    Jun 13, 2015 at 16:05

I was able to solve this by using a usb stick of yosemite. Appsrently the disk was not locked when I booted from it. This is only a 10.11 issue.

Thanks for your replies.

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