Buying Used: How to reformat prior to use?

Discussion in 'iMac' started by Robdmb, Dec 17, 2012.

  1. Robdmb macrumors member

    Nov 5, 2008
    I am gonna pick up a 2011 iMac (21.5 inch base model) for what I think is a great price. I was wondering what I should do to make sure the computer is entirely wiped clean and reformatted prior to use? Can anyone point me in the right direction? Thanks.
  2. eairlie macrumors newbie

    Dec 17, 2012
    or, to make things nice and easy for you, when starting it up, press and hold command - r till the apple logo appears, then use disk utility to wipe the hard drive and remove any partitions, then install Mac OS X :) that should get you where you want to be :)

    i should mention that you should make sure you have a bootable install disk or drive before doing this, so that you can actually install an OS :)
  3. Robdmb thread starter macrumors member

    Nov 5, 2008
    So I got my used mac and am trying to do the clean install and have a few questions. When I got into Disk Utility I see:

    1. 500.11 GB .....
    Macintosh HD

    Superdrive (greyed out)

    disk 1
    Mac OS X Base System

    Which should I delete to do a clean install and start fresh? Is the Mac OSX Base system the recovery partititon? Also, is it better to use the recovery partition or to do internet recovery? Thanks.
  4. Weaselboy macrumors Core


    Jan 23, 2005
    When you do a command-r boot to Recovery HD, the recovery partition is mounted and shown as "Mac OS X Base System", and that is what you are seeing. If you want a clean install, just erase Macintosh HD and reinstall the OS.

    Before you do that though, just be aware of something. Does the machine now have Lion or Mountain Lion?

    If the machine has Mountain Lion, but came with Lion from the factory, when you go to install the OS as I described above you will be asked for the App Store AppleID that was used to purchase Mountain Lion. Of course you won't have that since you don't have the previous owner's AppleID... and you will be screwed since you will have already erased the OS.

    Post up what you have now and I'll explain your options if you like.
  5. Tofray macrumors regular

    Mar 7, 2011
    When you say "screwed" does this just mean you have to install Lion, and then buy Mountain Lion again? or does it mean you won't be able to install any OS without the previous owner's AppleID?
  6. Weaselboy macrumors Core


    Jan 23, 2005
    Yes, I mean you will have to install Lion then buy Mountain Lion. The problem though is you will be running from a Mountain Lion recovery partition and that won't let you install Lion. You will need to boot from an external drive or USB key to format the entire drive and only then will you be able to get back to Lion. Thing is you will have already wiped the OS and will have to no way now to make a recovery USB key to boot from and erase the entire drive. This is the Catch 22 I was referring to.

    Newer machines are supposed to be able to get around this by bypassing the recovery partition and going to "Internet Recovery" with command-option-r at boot, but this does not seem to always work.

    You can read more about it here.
  7. Tofray macrumors regular

    Mar 7, 2011
    Thanks for the info, Weaselboy...What if I made a bootable USB drive before I tried to reinstall the OS? Would it be possible then to reformat the entire drive and get back to Lion (without the previous AppleID)?

    I read the link you sent (thanks) and it sounded like this was possible, but maybe I read it wrong.
  8. Weaselboy macrumors Core


    Jan 23, 2005
    Yes. If you completely wipe the drive it will default back to whatever OS version it came with and download that from Apple's servers. The default OS is tied to the serial number and not an AppleID.

    So if your machine came with Lion, that will install Lion then you will have to go to the App Store and buy Mountain Lion.

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