Installing OS 10.6.8 on a Mac Mini built for 10.7 – yes, it’s possible.

Installing OSX on a i5 Mini using Target Disk Mode

Man, do I hate OSX v10.7, aka “Lion.” Like, I really, *really* hate it. In a production environment, you don’t need a version of your everyday OS acting all hinkie… but that’s what Lion has been doing since I was forced into using it on a new Mac Mini I got about a month ago for dev.

After numerous attempts to wipe & install 10.6.8 (after having backed up files using a USB 3 duplicator, of course) using an external DVD drive, I was coming up dry. No luck, so it’s time to get creative.

Luckily, there’s a way to get rid of that nasty “not ready for primetime” OS as long as you’re not scared of getting your hands dirty. Here’s the methodology I used, based on this thread over on the Apple discussion boards… you’ll need the following:

• a new Mac Mini (referred to here as Mac #1) running OS 10.7 with either an i5 or i7 processor.

• another Mac (either MBP or iMac is fine, referred to here as Mac #2), as long as it’s fairly recent and has an installed i5 or i7 processor.

• the original OS 10.6 install discs that Mac #2 came with (those are the grey ones).

• a FULL RETAIL INSTALL version of OS 10.6 (that’s the one with the Snow Leopard on the cover)

• a FireWire 800 cable

The process…

1. Grab your Mini, and go to System Preferences » Startup Disk. Tell it you want to boot it into Target Disk Mode.

2. Hook up the FW800 cable between the Mini and your i5 Mac (for me, I used my 2.4 i5 MBP), and restart the Mini in Target mode. The Mini should pop up on your Mac’s desktop as an external disk.

Now, here’s where you get creative…

3. Launch Disk Utilities, nav to the Mini, and erase the entire disc. Personally, I always do a “zero out data” and (depending on time & existing data) possibly a low level format.

4. After the format & erase is done, pop the RETAIL version of the 10.6 installer disc into Mac #2, and hit “Install.” Tell it you want to do a new install of the OS on that Mini (that’s Mac #1) sitting on your desktop. Your Mac #2 will quit every open app and go into an install mode – this is okay. It needs to do this to install 10.6 on Mac #1.

5. IMPORTANT STEP: about 20-30 minutes into the install, Mac #2 will try and restart. HOLD DOWN YOUR OPTION KEY AT THIS POINT. Your Mac will be at a grey screen here, showing you available discs for booting. Here’s where you eject the retail version of 10.6, and pop in the 10.6 install disc that Mac #2 came with. Once that newly inserted 10.6 disc shows up, highlight the disc and choose it as your boot volume.

6. The install will pick up where it left off, installing all the i5 or i7 proprietary drivers along with the remaining 10.6 pieces. When the install is done, Mac #2 will want to reboot. Again, this is a good thing.

7. After reboot, the Mac will restart using Mac #1 (that’s the Mini) as the primary drive. Yeah, you might be *using* Mac #2, but you’re booted to the Mini so it’s all good. Run thru the registration process, then run all OS updates until you are running a full clean version of 10.6.8.

8. Select “Shut Down.” This will shut down Mac #2, but Mac #1 is still on and in Target mode. Push & hold the power button until the Mini shuts off completely.

9. Unhook the FW800 cable. You’re done.

10. Power up both Macs. Mac #2 is just as you left it, and Mac #1 is running a rock solid version of 10.6.8.

Let me know how your install goes in the comments!