Resolved Help - How to do a clean install of Mountain Lion on Mountain Lion

Discussion in 'Mac Basics and Help' started by phr33k, Nov 25, 2012.

  1. phr33k, Nov 25, 2012
    Last edited: Nov 25, 2012

    macrumors newbie

    Nov 22, 2012
    Hi guys,

    This may seem like a dumb question, but I have been searching for ages and can't get what I need. I used cmd-r and reinstalled OSX 10.8 from there, but i didn't realise it wasn't a clean install. All my apps and files are still there.

    My Air cam with Mountain Lion preinstalled, so how to I download it to do a totally clean install without paying for it in the mac app store as I don't fancy paying for it again? Or it it possible to do a clean install from the cmd-r?

    I really appreciate and help.

  2. macrumors regular

    Jun 14, 2009
    After booting with command-r did you use Disk Utility to erase the drive before running the Mac OS installer?

    An other way is to make a Mountain Lion Installer on a USB drive and use Disk Utility on that to Erase the internal drive prior to installation of the OS.
  3. thread starter macrumors newbie

    Nov 22, 2012
    Thanks for help. Yes i read that i need to erase it, however, where can i get a copy of the installer from? As surely when i erase it the cmd-r won't work?
  4. macrumors regular

    Jun 14, 2009
    If your Air is new enough and came with Mountain Lion Installed originally, restoring it will work with command-r even on an erased/empty SSD. (You need to have an internet connection when you do that - Internet Restore)

    You should also be able to (re)download ML without paying using your Apple ID if you paid for it originally and the restore partition can be created on an external drive using Recovery Disk Assistant:
  5. thread starter macrumors newbie

    Nov 22, 2012

    Excellent. Thats exactly what I needed to here. Cheers buddy
  6. thread starter macrumors newbie

    Nov 22, 2012
    Ok just to clarify, as I'm sure you can understand I am a bit nervous.

    If I erase my ssd using the utility on cmd-r, then reboot cmd-r and click on restore it will work when I am connected to the internet?

    Sorry if you are repeating yourself...
  7. macrumors regular

    Jun 14, 2009
    No problem. I understand that.

    If you want to be absolutely sure you can check whether or not your particular MB Air supports this recovery method by posting the question in the Air subsection of the forum but as far as I know this should work as long as you have an internet connection and everything goes as designed.

    Since you are completely erasing everything I'm assuming you have back-ups of your files.

    Start with cmd-r
    Use Disk Utility to erase the SSD
    Exit Disk Utility
    Install OS (Check that you still have an internet connection at this point - a clean System will be downloaded from Apple directly at this point)

    You should only have to restart after this installation

    If you want to erase the entire SSD including the recovery partition you need to start up from an external drive - which you can prepare to become the startup volume from which you initialise the re-installation of a clean OS as well.
  8. thread starter macrumors newbie

    Nov 22, 2012
    Thank you very much. It went exactly as it should. I erased the HD using the disk utility then reinstalled it using cmd-r. Now I'm back to a system lie when I got it. It will be handy to do this every year or whatever to keep it fresh.
    Thanks again.

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