Which means that if your Mac is running Leopard, and you're feeling adventurous, you can edit the SystemVersion.plist file so that it claims you're running, say, 10.6.8. The Mavericks installer--which will still need to be run on a Mac running Snow Leopard or later--will then install over Leopard without the slightest complaint. Here's how to do that:
- On your Leopard-equipped Mac (or, if you're trying to update an external hard drive--including a Mac in Target Disk Mode--that has Leopard installed, on that drive), navigate to /System/Library/CoreServices.
- Using a text editor that lets you enter an admin-user name and password to edit system-level files--such as the non-Mac App Store version of TextWrangler--open the file called SystemVersion.plist.
- Locate the ProductVersion key (not the ProductUserVisibleVersion key). Just below that is a string of numbers indicating the OS version; for example, on a Mac running OS X 10.5.8, it will read 10.5.8.
- Change that number to 10.6.8, save the file (providing your admin-level username and password when prompted).
- If you modified an external drive, and the Mac you're working on is already booted into Snow Leopard or later, you can launch the Mavericks installer immediately. If you modified your Mac's startup drive, you'll need to boot your Mac from a drive running Snow Leopard or later that also contains the OS X installer. (If you've created a bootable Mavericks install drive, just boot your Mac from that, and when the Install OS X screen appears, continue until you can choose your Leopard drive as the install destination.) Another approach would be to boot your Leopard Mac from an external drive containing Snow Leopard or later, and then run the installer from there. Yet another option, if you've got two Macs with FireWire or Thunderbolt, is to boot the Leopard Mac into Target Disk Mode and connect it to your Snow Leopard or later Mac, and then run the installer.
- If you aren't using a bootable Mavericks installer (in other words, if you're booted from a standard drive running Snow Leopard or later), one additional tip: As explained in my main article on installing Mavericks, when you get to the installer screen showing your internal drive, you need to click the Show All Disks button to show your Leopard drive, and then select that drive as the install destination.
Whichever approach you take, when you're done, you'll have Mavericks on your previously Leopard Mac.
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