jansigmon Said:
"Can’t install Big Sur on 2018 MacBook Air: Hello all, I face the same problem every time - after the installer is downloaded, installation starts and when the progress bar reaches 12 or 14 minutes installation interrupts with an error message[...]"
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Start with a Backup:
Important: Be certain to create a backup of your Mac prior to all of this. That way, you can have something to restore from the Mac from, should anything go wrong with the reinstall. Once reinstalled, see if all is complete.
Proceed from there with the following....
A. Create a Temporary Admin:
See what happens when you use a new administrator to install this. If it works, then there is an error in your current user.
B. Update in Safe Mode:
If you can't click something, then try it in Safe Mode [Hold Down: the shift key upon boot]. In Safe Mode, Login Items do not open at login; certain preferences are set aside; and damaged system files (i.e. caches) are fixed. Go Here: Start Up your Mac in Safe Mode - Apple Support
C. Use Ethernet:
On the computer, you connect it through Ethernet, going directly into your router. For a Mac (or PC) that does not have Ethernet, this would be the adapter to use: Belkin USB-C to Gigabit Ethernet Adapter - Apple
