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User profile for user: Cyokie
Cyokie Author
User level: Level 1
13 points

Returning to Mojave Without Proper Backup

This is kind of an extension of the last post I made, but some of the circumstances have changed. I want to downgrade from Catalina to Mojave. However, all the instructions I've found tell me that I must have a Time Machine backup from before I updated to Catalina. I only got this computer a week or so ago, and I updated it almost immediately, so the only Time Machine backup I have is from Catalina.


What do I do? If this means I can't return to Mojave while keeping all my data, is there a way to do so without backup? I'm aware this would mean losing all my files, but I don't have anything particularly important on my computer yet. Any help would be greatly appreciated!

MacBook Air 13", macOS 10.15

Posted on Feb 20, 2020 6:53 AM

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User profile for user: HWTech
HWTech
User level: Level 9
60,650 points

Posted on Feb 20, 2020 10:40 PM

You can copy the files you want to keep to an external drive. I don't use TM, but it may be possible to copy just the files from the TM backup after you reinstall macOS. It never hurts to have multiple copies of your data. Then boot into Internet Recovery Mode using Command + Option + Shift + R to boot the installer for original OS which shipped with your computer. You can also create a bootable Mojave USB installer.


Once booted to the Mojave installer launch Disk Utility and click on "View" and select "Show All Devices" so that the physical drive appears in the left pane of Disk Utility. Select the physical drive and erase it as GUID partition and APFS (top option). Once the drive is erased quit Disk Utility and select "Reinstall macOS". Once you have finished setting up the new OS just copy your saved files back.


Once you have Mojave setup you will need to erase the external TM backup drive as GUID partition and macOS Extended (Journaled) before using it to back up your clean Mojave installation.

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User profile for user: HWTech
HWTech
User level: Level 9
60,650 points

Feb 20, 2020 10:40 PM in response to Cyokie

You can copy the files you want to keep to an external drive. I don't use TM, but it may be possible to copy just the files from the TM backup after you reinstall macOS. It never hurts to have multiple copies of your data. Then boot into Internet Recovery Mode using Command + Option + Shift + R to boot the installer for original OS which shipped with your computer. You can also create a bootable Mojave USB installer.


Once booted to the Mojave installer launch Disk Utility and click on "View" and select "Show All Devices" so that the physical drive appears in the left pane of Disk Utility. Select the physical drive and erase it as GUID partition and APFS (top option). Once the drive is erased quit Disk Utility and select "Reinstall macOS". Once you have finished setting up the new OS just copy your saved files back.


Once you have Mojave setup you will need to erase the external TM backup drive as GUID partition and macOS Extended (Journaled) before using it to back up your clean Mojave installation.

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User profile for user: Cyokie
Cyokie Author
User level: Level 1
13 points

Feb 21, 2020 6:43 AM in response to HWTech

I think this may solve my problem, so thank you very much! There's just one thing I'm a little unclear on: Are you saying I need another external drive other than the one I use for Time Machine, or can I use that one USB for the entire process?


Sorry if this is a stupid question. I'm not great with computers.

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Returning to Mojave Without Proper Backup

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