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Still can’t install Big Sur

Trying to install Big Sur on a supported iMac. Download the installer from Software Update: Check. Install the OS: Check. Then the Mac restarts, shows the Apple logo and a progress bar, and after 2 minutes... restarts. And after 2 minutes: Restarts.

I’ve now downloaded the installer four times; I’ve run the installer from Safe mode; I’ve checked the Fusion Drive integrity several times using Hard Disk Toolkit’s First Aid and with Onyx. I’ve checked if the correct startup disk is used using the alt key during restart and choosing the installer partition. It Just Won’t Work. Every time I have to go back to Catalina using cmd-R during restart. This is getting weird. What can I do? Thanks!

iMac 27″, macOS 10.15

Posted on Dec 13, 2020 12:30 AM

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Posted on Dec 14, 2020 12:15 PM

Update: APFS was the culprit. When I tried First Aid on the drive, Hard Disk Utility kept telling me that it couldn’t help: “NX media keylocker data range is invalid” and “Container superblock is invalid”. Both of these errors appear to have something to do with the introduction of APFS a couple of Apple Systems ago (Google it).

I made a bootable USB drive with the Big Sur installer (https://support.apple.com/de-ch/HT201372 - apologies this is German), selected that drive as the startup drive, used Hard Disk Utility to format the Fusion drive, and then installed Big Sur... now I’m restoring my user data and programs from the Time Machine backup.

Pretty ugly update path, I must say. Well, problem solved, anyway. Maybe this will help someone else.

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Question marked as Top-ranking reply

Dec 14, 2020 12:15 PM in response to Karl Geiger

Update: APFS was the culprit. When I tried First Aid on the drive, Hard Disk Utility kept telling me that it couldn’t help: “NX media keylocker data range is invalid” and “Container superblock is invalid”. Both of these errors appear to have something to do with the introduction of APFS a couple of Apple Systems ago (Google it).

I made a bootable USB drive with the Big Sur installer (https://support.apple.com/de-ch/HT201372 - apologies this is German), selected that drive as the startup drive, used Hard Disk Utility to format the Fusion drive, and then installed Big Sur... now I’m restoring my user data and programs from the Time Machine backup.

Pretty ugly update path, I must say. Well, problem solved, anyway. Maybe this will help someone else.

Dec 13, 2020 9:03 AM in response to PRP_53

The Fusion Drive is one drive to applications. The fact that part of it is an SSD, and another part of it is a regular hard drive, is transparent to apps. I have no separate SSD partition. The OS takes care of moving stuff between the hard drive and the SSD, but that is not visible to apps - or to me (as the user). The drive has >350 GB free (=empty space). If Big Sur would not find enough space on the drive, regardless of where that space is physically located, it would complain about not enough space.

Dec 13, 2020 11:44 AM in response to Karl Geiger

Thanks!

I am currently running Catalina and that’s what I ran Onyx on, prior to my attempts at installing Big Sur. So no, I can’t have damaged my installation with Onyx.

I was also thinking that multiple restart might be ok, but after the first restart, when it’s showing the Apple logo and a progress bar and nought else, it’s restarting every 1:53 minutes... for ever. I stopped this after about 30 restarts, every one at 1:53, punctually as a clock, which no firmware update on the planet would require.


As there are quite a number of people with problems installing Big Sur, I think I’ll wait for the first update, download the installer again, and try again... if that doesn’t help I’ll call support.

Still can’t install Big Sur

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