New Mac with Mavericks, I want downgrade to Mountain Lion

If the Mac came pre-installed with Mavericks you can't install an earlier OS than the one on the computer when new 😟.

If the Mac previously had MLion and you upgraded to Mavericks you could restore from backup. If this is the case, and you need more info, please ask.

Is there a particular app you need Mountain Lion for, or some other reason? Maybe there's a solution whilst retaining Mavericks as the OS.

It's certainly not recommended to use a friends installer file. Mountain Lion was a paid for upgrade and is tied to a users AppleID not the computer (unless the computer had MLion installed when new).

Even if you were able to install a legitimate copy you would need to have bought your own version that is tied to your AppleID. What you're thinking of doing is probably likely to cause problems, apart from it being a bootleg copy of MLion.

Yes, the computer had Mountain Lion installed when new.

That's good news as you should be able to erase the drive and re-install Mountain Lion using Internet Recovery. IR should re-install the OS that was on the Mac when new.

This will erase everything on the drive, so if there is anything you need, ensure you have back up first so that you can restore your data.

More info here:

http://support.apple.com/kb/HT4718

Alternatively, did you make a Time Machine backup or a Clone of your HD before upgrading to Mavericks? If so, you can use that to restore back to the previous OS with your data intact.

😟 In that case I think you may have a problem installing an earlier OS than Mavericks.

Perhaps it would be worth calling AppleCare (you have 90 days free telephone support with your new purchase - 3 years if you bought the extended AppleCare). Explain that you need a Mac that will run Mountain Lion.

If the Mac is less than 14 days old Apple operate a 14-day returns, no questions asked policy.

Although this is just a guess, my hunch is because the Mac Mini hasn't been updated recently it might be able to run Mountain Lion, although the advice is always never install an OS earlier than the one on the computer when new. You don't want to do anything that might invalidate your warranty.

jmgaco wrote:

No, the computer that had Mountain Lion installed when new is the my friend´s computer (I have a flash bootable of this computer).

If you mean you have a bootable flash drive with a copy of the Mountain Lion installer on it, it may install that OS on the erased Mini's drive, assuming it will boot your Mini to begin with. On the first startup after installing that OS, as part of the setup process you should be asked for your Apple ID, which should link the license for that installation to you rather than to your friend.

But because this is unsupported & possibly a violation of the ML licensing terms, I agree that if possible you should call Applecare & discuss the implications of doing this before proceeding.

You also might want to consider buying an external drive & installing ML & Server 2.0 on it rather than on your Mini's internal drive, & booting from that for your certification work. That way, the Mini will still run its "native" OS when booted from the internal. To keep that system from being influenced by the ML one in any way, you should immediately unmount the internal drive after starting up from the external drive, or you can create an "fstab" file on the ML system with an entry to prevent the internal drive from mounting when starting up from the external.

I need Mountain Lion because I will install Mountain Lion Server over Mountain Lion, and I need ML Server because I want to study to pass an Apple Certification about ML Server 10.8

The difficulty here is twofold. First, we don't know whether Mountain Lion would run on that machine at all. Apple does not support running systems older than the one that a machine shipped with, because those older systems may not support the newer hardware.

Secondly, even if it would work, there's a very big legal issue involved with using a friend's copy of Mountain Lion. In fact, if we actually provided you with detailed instructions on how to do that, that would probably result in this topic being deleted by the moderators.

Fortunately, there's a very easy solution: install ML Server in a Parallels virtual machine. I keep a number of Lion and Mountain Lion virtual machines around for testing purposes, and this works quite well. Of course, the performance of those systems isn't what it would be if you were running them directly, but the beauty of it is that it doesn't really matter what your hardware is (as long as you have sufficient resources).

I'm surprised no-one asked "what Mac did you exactly buy"?

While the general advice you're been given is generally correct, that is, you cannot install an OS version older than the version that came with your Mac, there are instances when certain model are in fact able to run the prior version OS.

If, and this is a very big if, your computer model was released prior to the release of Mavericks and did not come with a special build of OS X Mt Lion 10.8.5 (that is it will run on a 12F45 build or earlier) then it's possible and worth a try. What you need to do though is be sure you're trying to install from a v1.3.29 Mt Lion installer that produces build 12F45.

The OP says he bought a new Mac Mini with Mavericks 10.9.

That'll teach me to not read everything exactly. 😀

Given that then I would expect Mt Lion to be installable as this was not changed at the time Mvx was released. How he goes about doing it is up to him but a simple way to do it without a 12F45 installer is to use Target Disk Mode from another computer, install Mt Lion from there, update it fully, then try booting directly from his Mac mini. Flash drive should work if he downloads and uses the newest version of the Mt Lion App Store installer.

I'm good at speed-reading as well 😁.

Thomas A Reed wrote:

Secondly, even if it would work, there's a very big legal issue involved with using a friend's copy of Mountain Lion.

It is possible the licensing issue could be resolved by buying a copy of Mountain Lionfrom the Apple Store. Technically, there are still problems actually getting that installed on the Mini but it might be worth asking Apple support about that.

And I still think the way to go, assuming the technical & legal issues can be resolved, is to install ML & Server 2.0 on an external HD, keeping it isolated from the "native" system on the internal drive in the Mini.

Install OSX Restrictions