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Hi,
I can not get Big Sur to install on my 2017 iMac 27inch. At first it would not update from Catalina with "an error occurred loading the update". After a few tries I erased the drive to start from scratch. I'm currently booting from an external Mojave system in safe mode and I have a fully downloaded version of the Big Sur install, but I'm still getting "an error occurred loading the update".
I would appreciate any advice. Thanks in advance.
If one still has the Full Installer of Big Sur - easy enough to make a Bootable Installer on a USB of at least 16 GB in size. Then shutdown computer and disconnect all external drives except the USB Installer you just created. Restart the computer and immediately hold the Option key. It will load the Boot Manager and present booting from Internal drive or USB Bootable Installer. Choose the USB Installer and again presented with options. Choose Install macOS - Big Sur installation will commence and just follow at the prompts with several automatic reboots until finally presented with the Setup Assist for Big Sur.
Sorry to say - No not the same. Just coping the Application Install Big Sur to the external drive does zero, nada nothing but storage on external drive
The Instructions from Previous post will make the drive Bootable Installer on a USB of at least 16 GB in size
Sorry for your frustration. These problems seem to come up fairly often. In most cases, what the problem turns out to be is that the download was done via Wi-Fi, which is really too slow for these very large files and the result is a corrupted installation file that will not load. (If it did, you would have operational issues.) Here is what I suggest you try. Put the installer into the trash and do another download. If you were using Wi-Fi to do the download, don't. It's too much data for Wi-Fi. Instead, you need to use an Ethernet cable directly connected to your modem/router. If necessary, temporarily move your computer to do the download. And during the process, stay off the internet. If you are unable to directly connect to the internet, then be prepared to do multiple Wi-Fi downloads until you get a good one that loads. And allow each download to fully complete, which can take up to an hour, more or less, plus another 45 minutes or so for the installation. Last, if you were using a browser to access the download link, only use Safari, not Firefox. Good luck. I hope it goes well.
Thank you so much for the reply! I did download the entire installer twice on ethernet but I guess that still could be the issue. For now I had to restore Catalina from Time Machine so I could work. I hope to be able to give this another try soon.
I tried the bootable install disk and it didn’t work either. Big Sur will not install on that iMac or even on an external drive attached to that iMac. I have another iMac at work. Using that second iMac I installed Big Sur on that same external.
Some time back I experienced a random shutdown. When I tried to restart I got a “no system” error. At that time I tried to format the internal flash/SSD but I would not work and any attempt to repair failed. Apple told me that I had a drive failure. All Apple stores in the area were shut due to Covid so bought an SSD to install a system to run externally. That worked fine. Eventually I took it to Best Buy (Apple still closed) and somehow they were able to reformat the drive. All has been fine until recently when it would not complete any system updates unless it was in safe mode, and then the Big Sur issue. It passes the hardware test with no errors.
Do you think I could clone the external system to the problematic iMac? Or any other tips?
Thank you so much. I really appreciate your help.
Fixed. It was a bad memory module. That was the most elusive problem I've ever encountered. Thank you for replying to my posts!
Good luck. I hope it goes well.
Thank you for the reply. I did boot from an external drive that had the full installer on it. It wasn't a dedicated bootable installer but I would think it's the same thing?
It might work but since there appears to be some Hardware issue - the problem may reoccur and the 11.4 once release.
Install fails on a clean internal drive
