Downgrade from Big Sur to Mojave - Success

[wstrohm]

For several reasons, I would like to downgrade MacOS on my computer at left from Big Sur 11.6.1 to Mojave 10.14.x. I would also like to use HFS+ on that installation instead of the "standard" APFS. For starters I have created a Mojave installer USB flash drive, using the "createinstallmedia" method shown for Big Sur with appropriate file name changes. This flash drive, with an EFI folder copied from my Big Sur computer (OpenCore 0.7.5), does boot Big Sur with no problems. But I realize this "project" may not work, and I have questions. [Edit 12/01/21: It does work, but as mentioned below.]

1. I have a web page that describes how to install Mojave 10.14.4 and change the "ConvertToAPFS" in "macOS install data" from True to False to use HFS+, but the procedure is for an actual Mac. It is somewhat like RehabMan's procedure for High Sierra, but I'm not sure it will work. Any comment on this part of the task? Is there something better? [Edit 12/01/21: This procedure does not work.]

2. The earliest MacOS that is supposed to work with an iMac19,1 is 10.14.6. My "Install macOS Mojave.app" is version 14.6.06. That sounds right for what I want, but can version 10.14.6 still run HFS+? [Edit 12/01/21: Yes... must install normally resulting in an APFS file system, but CCC can copy all to an HFS+ drive and all works fine on that drive.]

3. In general, is there any chance of this working? I'm pretty sure I can do this by using a standard installation (APFS) but don't want that. If I cannot use HFS+ on Mojave, I will try the same thing with High Sierra instead of Mojave, and use RehabMan's method of installing the HFS+ file system, which I know works (I have two computers using HFS+ on High Sierra). If I have to do that, I would probably have to change my SMBIOS from iMac19,1 to iMac18,3, as on my other computers. [Edit 12/01/21: Works on HFS+ with SMBIOS of iMac19,1.]

Thanks for reading; sorry if this is boring.

 

[Jamesbond007]

For several reasons, I would like to downgrade MacOS on my computer at left from Big Sur 11.6.1 to Mojave 10.14.x. I would also like to use HFS+ on that installation instead of the "standard" APFS. For starters I have created a Mojave installer USB flash drive, using the "createinstallmedia" method shown for Big Sur with appropriate file name changes. This flash drive, with an EFI folder copied from my Big Sur computer (OpenCore 0.7.5), does boot Big Sur with no problems. But I realize this "project" may not work, and I have questions.

1. I have a web page that describes how to install Mojave 10.14.4 and change the "ConvertToAPFS" in "macOS install data" from True to False to use HFS+, but the procedure is for an actual Mac. It is somewhat like RehabMan's procedure for High Sierra, but I'm not sure it will work. Any comment on this part of the task? Is there something better?

2. The earliest MacOS that is supposed to work with an iMac19,1 is 10.14.6. My "Install macOS Mojave.app" is version 14.6.06. That sounds right for what I want, but can version 10.14.6 still run HFS+?

3. In general, is there any chance of this working? I'm pretty sure I can do this by using a standard installation (APFS) but don't want that. If I cannot use HFS+ on Mojave, I will try the same thing with High Sierra instead of Mojave, and use RehabMan's method of installing the HFS+ file system, which I know works (I have two computers using HFS+ on High Sierra). If I have to do that, I would probably have to change my SMBIOS from iMac19,1 to iMac18,3, as on my other computers.

Thanks for reading; sorry if this is boring.

MacOS Mojave may be able to boot from a HFS partition, but it will not be able to install any updates if running from HFS. That is my previous experience.

So if you have reason to want to use HFS for booting MacOS, stick with High Sierra.

 

[wstrohm]

MacOS Mojave may be able to boot from a HFS partition, but it will not be able to install any updates if running from HFS. That is my previous experience.

So if you have reason to want to use HFS for booting MacOS, stick with High Sierra.

My installer (I think) will install 10.14.6. If that is true, and I recall correctly, that is the last version of Mojave anyway. If I wanted to return to Catalina or Big Sur, I also have those installers on flash drives. Two of my main reasons for picking Mojave were 1) it's the last version of MacOS that runs 32-bit apps, and 2) the earliest MacOS that will run iMac19,1 is 10.14.6 (again if I have that correct). I could run High Sierra, but would have to change my Generic Platform data in OpenCore to show iMac18,3, which is not as good a match to my hardware.

[Edit 12/01/21: Solution to this was to install to APFS, then used Software Update to update to Build 18G9323 which includes security update 2021-5, which is, I believe, the latest and last Mojave update. Then use CCC (version 5.1.28) to copy the entire OS to a HFS+-formatted drive. Voila, the final version of Mojave on HFS+.]

 

[wstrohm]

Because of my ignorance of Terminal syntax, the only thing I have been able to do is change the directory to my flash drive. Anything beyond that gives me "no such file or directory" when attempting to access "macOS install data" and/or "vi minstallconfig.xml" on the flash drive, per the linked web page's instructions. Any help, or are those files just not there inside "Install macOS Mojave?"

 

[jpz4085]

Anything beyond that gives me "no such file or directory" when attempting to access "macOS install data" and/or "vi minstallconfig.xml" on the flash drive, per the linked web page's instructions.

The procedure in the page you linked indicates this is to be performed on the internal SSD and not the flash drive. Examine the Volumes directory for the correct folder name as instructed in that guide. This is to be done following the first reboot in the install process.

 

[wstrohm]

The procedure in the page you linked indicates this is to be performed on the internal SSD and not the flash drive. Examine the Volumes directory for the correct folder name as instructed in that guide. This is to be done following the first reboot in the install process.

The steps in the procedure are for a Mac, of course, not a Hackintosh. I interpret them as follows:

Step 9/10 (do first): Set the BIOS boot order to select the "installer media" (USB flash drive) and select it as the boot source, then "save and exit" the BIOS and select the volume "Install macOS Mojave" in OpenCore. Then boot the computer from that.
Step 7: Format the target SSD using Disk Utility from the USB flash drive installer. Name it during formatting.
Step 12/13: Launch the Terminal app in the flash drive's Utilities menu.
Step 16: Change directory ("cd") to the target SSD's name.
Step 19: Type cd "macOS install data"
Step 20: Type vi minstallconfig.xml
... etc.

The problem with this is that step 19 changes the directory from the target SSD to another directory. That directory has to be on the flash drive, since the target SSD has just been formatted and is empty. And I cannot find it on the flash drive anywhere in its Contents folder.

 

[jpz4085]

The steps in the procedure are for a Mac, of course, not a Hackintosh.

Once you boot the installer the procedure described will work the same way.

Step 9/10 (do first): Set the BIOS boot order to select the "installer media" (USB flash drive) and select it as the boot source, then "save and exit" the BIOS and select the volume "Install macOS Mojave" in OpenCore. Then boot the computer from that.
Step 7: Format the target SSD using Disk Utility from the USB flash drive installer. Name it during formatting.

Make sure you don't omit the following steps otherwise there's nothing on the SSD to edit:

Step 8: Agree to the Terms and Conditions and proceed by selecting your newly formatted SSD drive. (i.e. begin the installation process)
Steps 9 to 11: Reboot from your USB drive and select the macOS installer again and NOT the SSD.

Proceed with your steps listed below:

Step 12/13: Launch the Terminal app in the flash drive's Utilities menu.
Step 16: Change directory ("cd") to the target SSD's name.
Step 19: Type cd "macOS install data"
Step 20: Type vi minstallconfig.xml
... etc.

As I just indicated above...

The problem with this is that step 19 changes the directory from the target SSD to another directory. That directory has to be on the flash drive, since the target SSD has just been formatted and is empty. And I cannot find it on the flash drive anywhere in its Contents folder.

You need to start the installation process THEN reboot and edit the directory on the SSD per the instructions.

 

[Jamesbond007]

My installer (I think) will install 10.14.6. If that is true, and I recall correctly, that is the last version of Mojave anyway. If I wanted to return to Catalina or Big Sur, I also have those installers on flash drives. Two of my main reasons for picking Mojave were 1) it's the last version of MacOS that runs 32-bit apps, and 2) the earliest MacOS that will run iMac19,1 is 10.14.6 (again if I have that correct). I could run High Sierra, but would have to change my Generic Platform data in OpenCore to show iMac18,3, which is not as good a match to my hardware.

By "updates" I mean all OS updates, including the security updates subsequently released by Apple for Mojave.

Actually, I am not even sure if the Mojave installation program will allow installation to a HFS partition. I remember the last time I did this I installed Mojave to an APFS partition and then clone the partition to a HFS partition using SuperDuper and it booted from that. But no updates, including security updates, can be installed once Mojave was on a HFS partition.

 

[wstrohm]

Thanks for the replies, I appreciate them. "007," I do understand.

You need to start the installation process THEN reboot and edit the directory on the SSD per the instructions.

Thanks, I thought you meant after the initial "boot" to the installer disk. Anyway, my current problem is that after selecting and clicking on the Mojave icon in the OpenCore window, the computer automatically reboots... but not to the Mojave installer disk, but instead to the Recovery volume on the SSD. I'm guessing that's because SIP is enabled and I need to disable it with the "csrutil disable" command. Is that correct? Can't get anywhere if the Mojave installer won't open.

[Edit: nope, disabling SIP didn't help... It still restarts after selecting and clicking on the Mojave installer in the OpenCore window, and the computer comes up on the Recovery volume, showing a Big Sur icon in case I want to reinstall BS. I could use my secondary SSD to format the primary SSD, but I have no guarantee that if I then boot on the Mojave installer it will finally open... I might wind up on my secondary SSD's Recovery volume. What now?]

 

[wstrohm]

Still no progress. Although I formatted my primary SSD using the Recovery volume on my secondary disk, attempting to boot on my installer disk immediately results in a restart, putting me on the secondary SSD's Recovery volume.

I have tried setting "FF0F0000" in the csr section of OpenCore, using Terminal on the Recovery volume of my secondary SSD to set "csrutil authenticated-root disable" (which it did), and "csrutil status" shows "disabled." Still I cannot open the Mojave installer. The Recovery log on my secondary SSD displays a full page of errors. The only option available is to re-iinstall Big Sur. I have run First Aid on the installer and it shows good, but there must be something from the Big Sur installation on my lone remaining SSD blocking it from opening.

It would appear that if I want to install Mojave, I will have to reformat my secondary SSD as well. Not good... backing up and migrating my data from an external WD "Elements" would be a first time for me. Lots of chances to screw up, and I'm known for that. Am I still missing something?