I have two computers -- the newest, a MacBook Pro, came with OS X 10.6, and the oldest, an iMac, is running 10.5.8.

In order to upgrade from 10.5.8 to Mountain Lion, one has to first upgrade to 10.6, so I thought I could just try the DVD that I got with my other computer to get this first step done. And it's not working (the installer says "Mac OS X 10.6 cannot be installed on this computer" although the computer appears to satisfy hardware all requirements--I wish this error message was a little more helpful).

Is it because of restrictions of the Mac OS X DVD? I suppose what I'm doing with it isn't exactly its intended use.

  • 1
    How old is the iMac?
    – nohillside
    Jul 31 '12 at 17:55
  • 1
    Do you already have OS X 10.8 installed on the Mac Book Pro?
    – MrDaniel
    Jul 31 '12 at 18:52

Generally and legally no, since the installer on the DVD is checking for machine specific model identifier for the MacBook Pro that the DVD came with as shown in this workaround .

Once the file is opened, scroll down about ¾ of a page and you will come across a series of strings named hwbeSupportedMachines.

Now, technically the DVD's that came with Macs included a standard Mac OS 10.x.x Install plus new drivers for hardware specific features for that new model, stuff that would not be known about or included in the 10.x retail install DVD Mac OS X versions (builds) for computers. Which means the OS that came with your Macbook Pro once its installed on the Mac Book Pro should include all it needs to run on the iMac too. You just have to get it there, which you could do via cloning a 10.6 install from the MacBook Pro to the iMac or maybe via installing OS X 10.6 on the iMac via the MacBook Pro using FireWire target disk mode.

Untested Solution if you want go the Upgrade path of 10.5 to 10.8 wihout erasing the iMac

  1. Backup important Data on iMac

  2. Boot the iMac into target disk mode, by holding down the T key while boot the iMac.

  3. Connect iMac to the MacBook Pro via FireWire

  4. Boot the MacBook Pro from its 10.6 Installer DVD

  5. Try to select for installation of OS x 10.6 the hard drive with 10.5 installed on it in the iMac.
    Note: This is the untested part, the Restore / Install DVD may not allow upgrades from prior OS X versions.

  6. Boot up the iMac and then upgrade to latest version of OS X 10.6

  7. Install OS X 10.8

Recommended Solution:

This will promote better performance via a clean install to a blank disk thus reducein legacy cruft and other left-overs from old OS X installs and old Applications, etc.

First thing upgrade the MacBook Pro to Mountain Lion, if you have not done so already.

Next back up all your files you want from the iMac, since OS X Lion / Mountain Lion will not be able to upgrade users from Mac OS X 10.5 to 10.8.

  • Create a boot able Mountain Lion install disk(using a hard drive or usb thumb drive)

    1. Open the Mac App Store, go to purchases and re-download the Install Mountain Lion Installer.

    2. Create a boot able disk drive by extracting the InstallESD.dmg from it to a external drive or partition. See How to create a bootable, backup Mountain Lion install disk

    3. Connect the external drive to the iMac

    4. Start the iMac while holding down the option key. Select the MTN Lion installer to boot from.

    5. Once the MTN Lion installer loads open Disk Utility and Erase the Hard drive in the iMac

    6. Quit Disk Utility

    7. Install OS X 10.8 by selecting Reinstall Mac OS X

  • Thank you! I was hoping Apple wouldn't have gone through the trouble of customizing the OS X DVDs that they put in the box of their computers to implement restrictions on the sort of thing I'm trying to do, but such is life!
    – Clafou
    Jul 31 '12 at 19:09

OS X is OS X is OS X. Yes, u can use the disk to upgrade your old machine, although not legally. There is no licensing to deal with, so it's rly easy and straight forward.

  • Thanks--but then if the DVD isn't checking for legitimate use (i.e. only accepting to run on the MacBook Pro model it came with), why do I get "Mac OS X 10.6 cannot be installed on this computer"? I don't remember when I got the iMac but I'd be surprised if it was unsupported.
    – Clafou
    Jul 31 '12 at 23:01
  • I'm pretty sure it's because it detects the current OS. Have you tried formatting your drive and then attempting the install?
    – Alexander
    Jul 31 '12 at 23:17
  • Mmm... No, I haven't tried. If that doesn't work then it will waste me quite a bit of time for nothing, so I'm wary of trying it. I mean, on the DVD there's a PDF that talks about upgrades, so it doesn't give the impression that it's a fresh install only DVD.
    – Clafou
    Aug 1 '12 at 10:43
  • 2
    According to hackint0sh.org/genuine-mac-support-147/… the installer is checking the Model Identifier, in the OP's case its something like "MacBookPro6,2" and an iMac will never equal that, hence the installer fails and puts up the "Mac OS X 10.6 cannot be installed on this computer" message.
    – MrDaniel
    Aug 1 '12 at 19:25
  • Your link both explains what's wrong and gives me a solution (alongside your cloning solution)--priceless, thanks again!
    – Clafou
    Aug 1 '12 at 19:59

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