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I'm in a somewhat odd situation: I need to wipe the disk of a MBP, but I can't boot into Recovery Mode/from a CD/etc. as there is a firmware password set.

Is there a way to wipe the disk from within the OS? (I guess the answer will likely be no, but I had to check). Or maybe just to "remove" the encryption password from the HD so as to make it unreadable?

I've been looking around and have found several ways of wiping files (srm, "Permanent Erase", etc) but if possible I'd like to be more thorough.

PD: A bit of background to explain how I got to be in this situation: I've been doing some work for a company where they use Macs so they've loaned me a laptop configured as per their policies (encrypted drive, firmware pwd, etc); once but I've finished the project I have to return the laptop but I'd like to clean it up as much as I can before handing it back.

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  • Are you doing that much of secret stuff non-work-related?
    – Rob
    Commented Feb 21, 2014 at 9:36
  • Even leaving the firmware password intact, your options depend on the OS level on the Mac and whether you have admin permissions. Can you elaborate on those two items with an edit?
    – bmike ♦
    Commented Feb 21, 2014 at 14:22
  • If the "disk" is really SSD and FileVault-ed, deleting the files and emptying the trash afterwards should be enough. If you're any doubt, create another (temporary) account and delete your original one just to make sure. This latter step would surely remove web history, caches, keychain etc.
    – adib
    Commented Mar 21, 2017 at 9:37

3 Answers 3

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You can just delete the files and use Disk Utility's Erase Free space feature to make them permanently gone. Open Disk Utility, go to the partition you want to clear, select the Erase tab and click on Erase Free Space... This will give you options that depend on your OSX version.

  • a slider with the settings Fastest, Secure and Most secure represent 1-pass, 3-pass and 7-pass wipes respectively.
  • radio buttons labeled Zero Out Deleted Files, 7-pass Erase Deleted Files and 35-pass Erase Deleted Files are quite self-explanatory

You may want to first go with a single pass to get an idea how long a single pass takes and then depending on your time allocation (or paranoia) choose between the multi-pass wipes. Note that 7-pass is good enough for NSA.

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I am not personally aware of anything, but then I haven't done any work with firmware passwords...

Just a thought though, can you take the drive out stick it in an enclosure and format it on another computer? I know it's not what you asked but it might do the trick if you have an external drive enclosure and another Mac (or even PC...)

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  • In the end, this is what I did -- as it was a MBP15 (not Retina), it was physically possible... On a Retina I guess I would have been a bit more "stumped"...
    – JJarava
    Commented Jun 2, 2014 at 9:59
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Depending on the age of the Mac you may be able to bypass/remove the firmware password.

Do you have a second hard drive available and administrator access? If so then give this a shot, I'm giving you a general workflow but feel free to ask about individual steps and I'll do what I can to answer them...

  • Connect an external hard drive (USB, Firewire or Thunderbolt, assuming it's an Intel Mac).
  • Use Disk Utility (Applications/Utilites/Disk Utility) to format the external hard drive as Mac OS Extended (Journaled). This WILL destroy any data on the external drive, be sure to save anything important beforehand.
  • Install a Mac OS onto the external drive. Mavericks is free, if the loaned Mac can support it then you can download it from the Mac App store. During the pre-installation process you are asked to choose the destination, choose the external hard drive.
  • Set the external hard drive to be the startup disk in System Preferences > Startup Disk
  • Reboot your Mac, assuming all of the above steps were done it should boot to the new system on the external disk.
  • Use Disk Utility to erase the Mac's internal disk

Hopefully that makes sense. That's the general workflow I've used before to help people in similar situations (need to erase firmware locked Macs) albeit I've already had a bootable external disk available. Feel free to ask for clarification on any steps and I'll edit my answer.

Alternately... If you're only concerned about your user data, and have been organized enough to keep the user data in your user folder and have administrator access then you can create a new user and remove the original user account. When you remove the user account you are given the option to remove the user folder (which would remove the sensitive data), along with a checkbox to remove it securely, which will write 0's over all of the data.

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