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Selling MacBook Air

Discussion in 'MacBook Air' started by Yankeesxd, Jun 25, 2013.

  1. macrumors member

    Hi if I want to sell my 2012 MacBook Air how can I restore my air back to factory settings?thanks
  2. macrumors regular

    Command-R on startup - reinstall the OS. Also a good idea to to a disk secure erase using the disk utility that comes up after the Cmd-R key as well.
  3. macrumors member

    Alright thanks for the help! This will prevent the future owner from seeing the things i had before or my passwords right?
  4. macrumors regular

  5. macrumors member

    secure erase greyed out

    I too am selling my 2012 MBA but the secure erase option is greyed out. Googling surfaces many confusing suggestions for many different models and years of MacBooks -- including the notion that SSD drives don't need secure erasing -- so I am curious to know what specifically works for the 2012 MBA.

    I tried running secure erase from a 2013 MBA connected via thunderbolt to the 2012 MBA in Target Disk mode, but that estimate grew to 19 hours remaining after already running overnight (which was only a 3 hour estimate as I went to bed). So I aborted that.

    Also, it seems my MBA 2012 is incapable of booting from a USB 3.0 key with either RecoveryDiskAssistant.dmg or Lion InstallESD.dmg restored to it. (Holding down option while booting does not surface the key as an option.) Does USB 3.0 only work when booted in non-recovery mode into OS X proper?

    My next act of desperation is to either try the terminal command:

    diskutil zeroDisk /dev/disk0
    and see how long that takes.

    Or I could just try reinstalling Lion fresh and see if secure erase is un-greyed after that. If the damn USB 3.0 key could just boot I could install without the long wifi download.

    It feels like everything is trying to delay my sale of this MBA.
  6. macrumors 68040

    In my MBA... the "secure erase" is grayed out too... but in the top header... there is an "unlock" icon. Clicking that and typing an administrator password unlocks the drive and the secure erase feature is enabled.

  7. macrumors member

    Damn, I didn't see that, so I did the Terminal command. It worked. Still don't know why I couldn't boot from the USB 3.0 stick, so I've stopped trying. System is ready to sell.
  8. macrumors 68040

  9. macrumors 6502a


    From link above: I'm very interested in learning more about this as to why it doesn't work - Anyone?

  10. macrumors 68040

    I think, but I'm not 100% sure, that it has to do with wear-leveling of the Flash Memory. Here's a quick and dirty run down of flash memory.

    A flash memory chip might have 110 blocks where data can be written, but the stated capacity is only 100, 10% extra.

    Say you write (create) a file that it 4 blocks. So the chip writes your data on blocks 1-4. As you add data, it randomly fills up the blocks. But when you go back and edit the first file created (1-4), it might not save it in the original location, it might save it in 105-109.

    The SSD tries to avoid writing data in the same place multiple times in order to preserve the limited number of write cycles (about 100,000-200,000 times, maybe more, but it used to be a lot less).

    Anyway, SSD support is still more or less a hack on any operating system because the File Systems we use (HFS, NTFS, FAT) are older and were designed for traditional hard drives. So the older method of secure delete (overwriting with random data) don't necessarily work because the SSD wants to spread the write across the drive (and could potentially miss data). In theory, you could have 10% of that data that doesn't get properly erased.

    The method I describe in the guide is different because it encrypts the entire disk and destroys the key used to unencrypt the data. The guide method doesn't erase the data (and only overwrites a portion of it during the reinstall), but your data isn't accessible to anyone (save, perhaps, FBI-, CIA-, NSA-type organizations; but they probably have all of your data anyway. ;))
  11. macrumors 6502a


    I think you have something here. SSDs move your data all around and when you hit delete you only remove last known location, leaving past versions wide open.

    Encryption and re-install does look like the most efficient way to go.
  12. macrumors 68000


    Where do you see the disk secure erase? If I install everything and then restart and erase the disk again, does it wipe the OSX?

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