Erasing SSD in MacBook Air?

Discussion in 'MacBook Air' started by iUseMacBooks, Aug 13, 2015.

  1. iUseMacBooks macrumors member

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    #1
    Hi,

    Over the past 6 months or so I've been debating on what to do with my MacBook Air. I've come up with a plan for what I finally want to do, but I have one problem.

    First off, here's my plan: I have an Early 2014 11.6" MacBook Air -- 4 GB of RAM and 256 GB SSD. I'd like to sell it and get a 13.3" MacBook Air.

    To do this, I'd first get an external hard drive (via USB 3.0) and take all of my info from the 11.6" to put onto the 13.3" But if I sell my 11.6" (even if I wipe it clean) I've been told that an SSD doesn't actually completely erase?

    That's my biggest problem at this point. I've been through giving a Mac away before but it was a different story. I had a MacBook Pro that I wiped clean and gave to my cousin. But now I've read an SSD doesn't erase like a traditional hard drive. So, if I can't wipe the SSD clean of my personal info, I obviously wouldn't want to sell it to someone.

    Does anyone know how I can safely and completely wipe the SSD clean? I figure if I can't find a solution, I'll go to the Apple Store and seek help.

    My 11.6" MacBook Air is in great condition, I only use it for college, and I don't do any heavy lifting with it (such as video or photo editing). The only reason I want to sell it is because I'd like to have the 13.3" screen. I'm ready to upgrade, but first I have to figure out this SSD-erase issue.

    If anyone has an advice or first-hand experience with this, I'd greatly appreciate help. Thanks.
     
  2. prisstratton macrumors 6502

    prisstratton

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    Winnipeg
  3. iUseMacBooks thread starter macrumors member

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    #3
  4. motrek macrumors 68020

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    Sep 14, 2012
    #4
    Not sure if that diskutil command line does anything more than what secure erase would do in Disk Utility.

    IMO a fairly good way to erase an SSD is to fill it up by copying a large compressed file to it (like a rip of DVD movie, or a ZIP file of a bunch of MP3s) and then duplicating that file until the disk is more or less full.

    Then delete all the files and your SSD should be effectively wiped.
     
  5. Weaselboy Moderator

    Weaselboy

    Staff Member

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    Jan 23, 2005
    Location:
    California
    #5
    Follow these steps...

    First go into System Preferences and in the Security & Privacy pane turn on FileVault encryption and wait for the encryption to finish.

    Now restart and hold command-option-r at boot. Once you select your wifi, you will see a spinning globe while the recovery utility downloads. Once in recovery, go to the Utilities menu and launch Terminal. Then type in the command below including the quotes (I am assuming the default volume name).

    Code:
    diskutil cs delete "Macintosh HD"
    That will kill the encrypted FileVault volume.

    Now start Disk Utility and go to the erase tab and format the drive to Mac OS Extended (Journaled).

    Then quit Disk Utility and click reinstall OS X at the top. This will download the OS version that came from the factory.

    Once the OS is installed and the setup utility starts, just power down.

    What this does is encrypt all your data then delete the encrypted volume, then after that erase over top of it. Nobody is getting your data after that.
     
  6. motrek macrumors 68020

    Joined:
    Sep 14, 2012
    #6
    Not so sure about that.

    If I'm not mistaken, turning on FileVault will read your data, encrypt it, and write it back. On a hard drive, it would be written to the same location, effectively overwriting your unencrypted data and making it unrecoverable.

    With an SSD, blocks get remapped so if you write data back to the same logical location on the "disk," it will hardly ever get written to the same blocks of the SSD.

    The end result is that your SSD will contain your encrypted data AND your unencrypted data simultaneously, and your unencrypted data will still be recoverable.

    My suggested method of duplicating a big file until the drive is full gives you a better shot at overwriting all the blocks of an SSD (all that data has to go somewhere...) and thus making the previous data unrecoverable.
     
  7. Weaselboy Moderator

    Weaselboy

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    #7
    When you turn on FV2 it encrypts the entire disk. The data is all placed inside the encrypted "container" so to speak. So even if someone were able to restore parts of the encrypted volume we deleted, the data would still be encrypted.

    The FV2 operation encrypting the entire volume accomplishes the same thing as overwriting everything as you suggested, just in a different way.
     
  8. motrek macrumors 68020

    Joined:
    Sep 14, 2012
    #8
    But my point is that overwriting doesn't work on an SSD... you think you overwrite something, but you're really writing to a different part of the drive, and the old part still exists and is recoverable.

    The only way to ensure that you overwrite everything is to fill the disk up. If this is what FV2 does, then great. In other words, does it make a "container" the size of the entire drive and fill it all up with random data?

    I suspect this doesn't happen, because it would prevent TRIM support from working on SSDs.
     
  9. Weaselboy Moderator

    Weaselboy

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    #9
    Yes... and that is my point. It does fill the entire drive with the encrypted volume.
     
  10. motrek macrumors 68020

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    Sep 14, 2012
    #10
    Not to disagree but I wonder how that's at all possible. It means TRIM support would be irrelevant, since all the blocks would always be full.

    I've always had FileVault turned on on all of my Macs. I noticed that writes to my 3rd party SSD in my Mac Mini were getting really slow so I enabled TRIM and performance improved immensely. So I think TRIM does work with FileVault somehow, which points to FileVault not taking up the whole drive with its encrypted DMG or however it works.
     
  11. Weaselboy Moderator

    Weaselboy

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    #11
    It does fill the whole drive. You can look in Disk Util and see that the encrypted volume has filled the drive.

    Here is mine from DU with FV2 on. Inside the encrypted volume I actually have about 55GB free.
     

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  12. ET iPhone Home macrumors 68040

    ET iPhone Home

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    Location:
    Orange County, California USA
    #12
    Can you make a recommendation?

    I'd like to erase all the content of my 2011 MBA so I can give my MBA to a family member, however I'd like to keep my purchased Microsoft Office which contains Word, Excel and Powerpoint so they can use it and not have to repurchase it. Can this be done?
     
  13. Weaselboy Moderator

    Weaselboy

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    #13
    Heck, if it is just a family member, I would create a new admin user account for them, then login to that account and from there delete your account and all its data.

    That would remove your personal data and leave Office intact for them.
     
  14. ET iPhone Home macrumors 68040

    ET iPhone Home

    Joined:
    Oct 5, 2011
    Location:
    Orange County, California USA
    #14
    Thank you! I never thought about creating a new admin. user acct. I'll try this, but I was under the impression that their can only be 1 admin. user, not more than that, but I'll try and see.
     
  15. rigormortis macrumors 68000

    rigormortis

    Joined:
    Jun 11, 2009
    #15
    your two options are either:

    turn on file vault 2 , erase the disk and lose the key
    or
    physically destroy the flash chips

    technically speaking, when you erase any iPhone from the 3GS to the latest model, all your doing is losing the keys.
    iphones don't erase the entire disk. this would take several hours. they haven't done this since the 2g/3g

    if you worry about erasing and writing junk files on your mac book but not worrying when you sell your iPhone 5, well hmmm!!! its the same thing!
     
  16. Weaselboy Moderator

    Weaselboy

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    #16
    Yep... you can create as many accounts as you want and they can all be admin accounts.
     

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