Partition Mojave HD to run Sierra

Started 3 months ago | Discussions thread
ChrisLumix Veteran Member • Posts: 3,361
Re: 2 things come to my head

silentstorm wrote:

ChrisLumix wrote:

"Especially true if the hardware comes with the newer OS, the firmware in the hardware will block any OSes that are older than the shipped version."

What you said is going back to the original OS that shipped with the hardware. You can't go back older than the shipped version.

If OP MBAir comes with Sierra, then yes, he can reformat his drive and get back the original OS. But if it comes with Mojave, then there's no way he could run Sierra on it, the firmware will block out Sierra.


I just checked, OP MBA laptop is a 2017 model. If it comes installed with Hi Sierra (original shipped OS), then he can't go to Sierra at all.

That's only partly true. My original 2011 iMac shipped with Lion. The supplier was able to erase and reformat the HD and install Snow Leopard on it. That model (not that machine) originally came with Snow Leopard, though later sales were shipped with Lion.

So the "shipping" point is not as moot as which particular OS the model in question FIRST SHIPPED WITH. Later examples may ship with a later OS but that doesn't mean the original OS for that model can't be installed.

No. It is very true. What you and Albert experienced is timeline down the road OS updated, and considered going back to original OS as older OS. Your supplier updated older machine to Lion and sold it to you. You as the customer perceived it as default OS from the shipped machine, but in actual fact it was updated w/o your knowledge.

My Air was bought on 1 week Aug 2011, and was shipped with Lion (end July 2011 released). I cannot get it back to SL. The firmware blocked everything.

For OP case, if his Air came with Sierra, or similar to your case the Air was updated to Hi Sierra from an older machine before shipped, he can go back to original shipped OS. If his Air was bought later in Nov 2017, he can't go back any older than Hi Sierra. For us to know what is what, OP need to test it out himself to see if a wiped drive can install Sierra. All we can do here is speculate over his situation. Hopefully he would update us on his progress.

Coming back to the timeline, if anyone were to buy a new apple computer today shipped with Big Sur, what would you consider as older OS? Big Sur? Since Monterey was already announced?

Yes, you must be right. My 2011 iMac came with 10.6.6 originally - when I got hold of the 10.6.3 DVD, which was the last 10.6 disk issued - it wouldn't install it onto an external HD . I'd forgotten about that, but there was some trick that let me do it in the end, though I can't now remember what that was.

(Ah, my filing system came to the rescue - here's what I had to do!):

• Use Disk Utility to make a read/write DMG of a 10.6.7 install disk for a MacBook Pro or iMac.
• Insert a 10.6.0 or 10.6.3 OSX retail installation disk in your DVD drive and use the Finder to open the disk to system/Installation/Packages/
⁃ open a Finder window of the 10.6/10.63 Installer disk, then press Shift-Cmd-G - in the popup type
⁃ System/Installation/Packages (no trailing "/") and press return, it will show the content of that hidden folder.
⁃ You will have to do this again, in another window, for the 10.6.7 Installer disk.
• One of these package files is OSInstall.mpkg which is the set of instructions for the Installer. This file in the 10.6.7 Installer is where the checking is done to see if it's installing to the 'correct' computer.
• Open another Finder window, and navigate to the same place in the 10.6.7 Installer. Replace the existing OSInstall.mpkg file with the one from the retail disk plus copy over all the printer related Installer packages. We do this because the retail installation script won't install the 10.6.7 printer packages. Check the 'copy all' box when the Finder warns you that the files already exist.
• Open Disk Utility and plug in an 8 gig thumb drive. Find the drive on the left side of the Disk Utility window and click on it. Now click Partition, chose 1 Partition, give it a name and click the Options button. Choose the GUID partition choice and close the window. Click the Partition button. When the Disk Utility is done, use SuperDuper or Carbon Copy Cloner to clone the modified 10.6.7 Installer to the 8 gig keychain drive. I had problems getting the Backup utility in Disk Utility to do this. You can boot any ready for Snow Leopard Mac with this Installer..

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Panas0n!c Lum!x LX100, TZ60

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