Failed Upgrade Big Sur iMac (Retina 5K, 27-inch, 2017)

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8 points

Failed Upgrade Big Sur iMac (Retina 5K, 27-inch, 2017)

Hello.

I’m trying to install Big Sur, as prompted by my iMac. It downloaded OK, and took me through licence accepting etc.

It then proceeded to a black screen with Apple logo and a progress bar. The progress bar is stuck at about 10%.

The machine is stuck in a loop of restarting, perhaps every 1-2 minutes. The mouse pointer appears top left after a short delay.

It has been like this for 4 hours.

I tried forcing power down with power button, then restarting. No change.

Any thoughts welcome!

Thank you in advance.

iMac Line (2012 and Later)

Posted on Nov 17, 2020 6:55 PM

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Answer 1

Top-ranking reply

HenryBevan Author

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8 points

Nov 18, 2020 6:22 AM in response to PRP_53

Thanks to all those who replied. I contacted Apple support. Following many attempted reboots, internet restore, Disk Utilities... sadly we had to reformat the fusion drive, rebuild it (using some Terminal wizardry), and install a fresh copy of Big Sur. I would perhaps recommend anyone else considering Big Sur wait a little while...

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Answer 2

HenryBevan Author

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8 points

Nov 21, 2020 2:33 PM in response to darthg1nger1977

Sure.

Strange things started happening to the disk and we couldn’t work out why. I haven’t done anything unusual to the computer so this was all down to the BS installer.

We booted into recovery, and tried disk utilities. The disk wasn’t happy - first aid failed. Etc.

Then following another reboot we got the grey question mark icon of death. Really not good.

It turned out the installer had managed to split the fusion drive into two somehow. We followed the instructions here...

https://support.apple.com/en-us/HT207584

That fixed the HD (formatted) and we were able to install BS from

internet recovery.

Hope that helps / is of interest.

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Answer 3

HenryBevan Author

Level 1

8 points

Nov 18, 2020 12:40 AM in response to rkaufmann87

Thank you for your help. Sadly the outcome is the same. It briefly showed me a circle with diagonal line and a url for support.Apple.com/startup (I think) b it then continued with a promising looking startup... but I am Now back to the same loop.

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Answer 4

Nov 20, 2020 4:27 PM in response to HenryBevan

Hi, I had exactly the same thing but managed to restore via a USB stick installer for Catalina, on which I will stay for a while.

May I ask what was done to the Fusion drive? I erased mine as part of my efforts to save Big Sur but it didn't work, in fact I ended up getting corruption errors when using the Disk Utility, it couldn't re-mount the volumes, and I feared the worst.

Glad you problem was sorted.

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Answer 5

rkaufmann87

Level 10

144,006 points

Nov 22, 2020 8:27 AM in response to HenryBevan

HenryBevan,

You have a failing HD, that needs to be replaced ASAP!!!!!!!!!!! Big Sur, Catalina, or any other Mac OS did not cause that, it is mechanical in nature. If you ignore the HD it will fail and you stand a good chance of losing data.

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Answer 6

Nov 22, 2020 11:32 AM in response to rkaufmann87

I think it’s clear the problem here is big sur, the hdd in my case and Henry’s worked fine otherwise, and perfectly for me. I installed Catalina again and Henry got big sur going, meaning the hdds worked albeit with different treatments. plus the big sur installer behaved exactly the same for us both on the same spec of Mac.

Also big sur is widely reported as problematic.

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Answer 7

HenryBevan Author

Level 1

8 points

Nov 22, 2020 11:49 AM in response to rkaufmann87

Hi there.

I guess it is a possibility, but because the Hd was absolutely fine, and now seems OK again afterwards, the finger seems to point to the upgrade process.

And hey, if I lose data, I’m practiced now at installing from fresh :-)

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Answer 8

rkaufmann87

Level 10

144,006 points

Nov 17, 2020 7:53 PM in response to HenryBevan

Please reset the NVRAM and then try again.

How to reset NVRAM on your Mac

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Answer 9

PRP_53

Level 10

91,711 points

Nov 18, 2020 2:44 AM in response to HenryBevan

Try shutting down via Power Button. Disconnect any attached devices except keyboard and mouse. Startup and immediately hold Shift key ( Safe Mode ) and hope it will finish installing.

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Answer 10

rkaufmann87

Level 10

144,006 points

Nov 18, 2020 7:40 AM in response to HenryBevan

Big Sur is pretty stable, however if you are attempting to upgrade on a damaged computer (in your case an unfused Fusion drive) you will have trouble.

However, I'm glad to hear you sorted it out.

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Answer 11

Nov 22, 2020 11:26 AM in response to HenryBevan

Excellent thank you

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Answer 12

rkaufmann87

Level 10

144,006 points

Nov 22, 2020 12:39 PM in response to darthg1nger1977

Well not correct, but if that is what you want to believe okay.

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Failed Upgrade Big Sur iMac (Retina 5K, 27-inch, 2017)

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