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How can I do a clean install of Mountain Lion?

I have an older MacBook Pro that I'm selling. I upgraded to Mounbtain Lion, but there was not an option to do a clean install (wiping everything clean and starting fresh). I want to do this to make sure all of my data is removed before I sell it. How can I do a clean install of Mountain Lion in order to accomplish this? In the past, from DVDs, it was easy. Thanks!

various macs, Mac OS X (10.4.9)

Posted on Sep 11, 2012 8:43 AM

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14 replies

Sep 11, 2012 2:17 PM in response to Budrew

Budrew wrote:

Sure, but I would imagine that it will be common for people to sell their Macs with upgraded OSs.

Doesn't apply to machines with Lion or ML unless they shipped with them. My advice is wipe the disk with DU, zero out the data, and sell it with the discs that shipped with it and instructions on how to install the software. Let the buyer deal with upgrading and adding 3rd-party apps.

Sep 11, 2012 3:04 PM in response to baltwo

So this is how it works under the recent OS's? I doubt most people want to buy a used Mac without an OS on it. There must be a way to deauthorize the OS and allow the buyer to re-authorize it. By the logic I'm reading in this thread the (newer versions of the) OS are tied to an iTunes account and are not simply part of (installed on) the computer. So, in theory, you can sell your hardware but not the software, the OS, on it. Does not make sense to me.


I will look in the box and see what OS it came with.

Sep 11, 2012 3:15 PM in response to Budrew

OK, so I tried to install the OS that came on the original DVD. Apparently, I'm not allowed to do that since I have a newer OS. It simply won't allow it.


So, I'm very confused. I cannot attempt a simple clean install of the Mountain Lion OS (unless I follow the somehwat technical instructions above) and I cannot install a previous OS.


So... I will try to "Boot into the recovery patition and use Disk Utility to format the boot drive, then install" the OS that came with the Mac in the first place.


Wish me luck!

Sep 11, 2012 3:44 PM in response to Budrew

OK, so I tried to install the OS that came on the original DVD. Apparently, I'm not allowed to do that since I have a newer OS. It simply won't allow it.


So, I'm very confused. I cannot attempt a simple clean install of the Mountain Lion OS (unless I follow the somehwat technical instructions above) and I cannot install a previous OS.

That's because you're not doing it correctly. You can't run an older OSX installer from a newer one. You can't install and older OSX on top of a newer one.


Put the first Grey disc that came with your Mac into the DVD drive. (Disc no. 1)


Then restart the Mac while holding down the "C" key. That will boot your Mac from the DVD. It takes a longer time to boot.


After it boots, access Disk Utility and Erase/repartition your hard drive.


Then quit Disk Utility and proceed with the install.

Sep 11, 2012 3:43 PM in response to Budrew

It was not as straightforward but it is working. I had to reboot from the Snow Lion DVD and use the Disk Utility there to erase the hard drive, and then install that OS again. As long as Mountion Lion is installed in any form it does not allow anything else prior to it to be installed (maybe that's how it's always been).


At any rate, I'll sell the trusty old MacBook Pro with Snow Lion and let the buyer do what they want with it.


Still, I'm wondering, if an OS is tied to an iTunes account, how will people sell ther old Macs in the future?

Sep 11, 2012 3:49 PM in response to Budrew

Budrew wrote:


Sure, but I would imagine that it will be common for people to sell their Macs with upgraded OSs.

That was only OK when you bought the Upgrade DVD and included both the original system discs and the disc you used to upgrade the OS.


Since Apple has now gone to the Download only model of OS X you now always need to install the Original OS or an Upgraded version that you have the DVD disc for.


If a Mac came with Leopard and you upgraded to Snow Leopard and then to Lion or Mt Lion you must remove Lion or Mt Lion and reinstall either Leopard or Snow Leopard and include all the discs for that system, Originals and the Upgrde Snow Leopard DVD.


If your system came Snow Leopard and you installed Lion or Mt Lion thenn again you remoeve Lion or Mt Lion and reinstall Snow Leopard and include the original discs that came with the system


If your system came with Lion and you upgraded to Mt Lion then you remove Mt Lion and reinstall Lion.


The reason for all of that is because with the Download only OS all upgrades are TIED to YOUR Apple ID, not to the computer. So the new owner can not reinstall Lion or Mt Lion, whichever you upgraded to, without using your Apple ID.

Sep 11, 2012 4:33 PM in response to Budrew

Budrew wrote:

At any rate, I'll sell the trusty old MacBook Pro with Snow Lion and let the buyer do what they want with it.

The others discussed the nuances with this new, since Lion delivery system, but if you've not finished installing, when the computer restarts and starts the setup process, quit it, and it should shutdown the machine. The next time it starts, the OP will get the virgin welcome screen. Otherwise, you'll have to create an admin account and that's just a PITA to deal with.


For another variant, see http://discussions.apple.com/thread.jspa?messageID=11927841#11927841

How can I do a clean install of Mountain Lion?

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