I followed this article. Now I'm on 10.15 Beta (19A512f), which I think it is beta 4, I'm trying to restore a timemachine backup of mojave(10.14.5).

My question is do I have to erase my entire disk to go back to mojave. I somehow managed to erase once before on a different machine. When I entered recovery mode again right after erasing, it seems like it tried to download a large image for a bare machine only using internet, but the timer stuck at 24:00. Basically, I couldn't access to mac OS utility at that time. Now I'm experimenting on another machine, and I don't want same thing happen again.

But as I skip Reformat and partition your startup disk step, I jumped to Restore from your Time Machine Backup step. I found that I have to choose between two destinations to restore, which I think it's something new brought by Catalina. Other the my backup drive, there are two other options. One is called Macintosh HD, the other is called Macintosh HD data. Both get similar info, I don't know which one it should be. So back to my question, do I have to erase entire disk. If I don't erase, which disk should be selected as restore destination. If I have to erase, does it mean the original OS installer on the disk would be gone as well, therefore I have to download the image from internet? But still after erase, do I still need choose between those two destinations? If so, which one.

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I need to get back to stable version ASAP, so I can't simply unenroll the device and simply wait for Catalina release. And I also turned genius bar guys for help, they said Catalina bring security feature, they can't help me restore factory setting(install Mojave) either. Plus they said using beta version means you have to deal with issue yourself. Any solution other than these would help.

Thank you guys

  • 2
    The article you linked states you have to do a complete re-format. Catalina partitions in a different way to Mojave.
    – Tetsujin
    Jul 29, 2019 at 16:01

1 Answer 1


Unlike some installations of some operating systems there is no OS level uninstall feature in macOS.

  • That is true for applications, though some do have uninstallers available.
  • That is true for minor OS version upgrades, EG 10.14.1 to 10.14.2
  • That is especially true for full versions, EG 10.14 to 10.15

What that means is that if you install an OS update or upgrade and you need to revert back to the previous version there is no built-in way to do so.

In fact the ONLY way to revert any OS upgrade is to back up your files, boot into recovery mode (or a bootable USB installer), wipe the drive and re-install the operating system. Once that is done you can restore from your backup.

  • I followed exactly the article says, I won’t be able to proceed after choose partition. If I choose reformat as APFS(encrypted ), the “apply” button is grey . If I choose APFS, I can click “apply”, but it prompts me with internal error partition failed.
    – ychz
    Jul 29, 2019 at 17:21

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