Apple offers solutions for problems when reinstalling Big Sur

In addition to the issues with the 2013 and 2014 MacBook Pros during the Big Sur upgrade, Apple has released a document for those users experiencing problems preparing the Big Sur update.

Says apple

If you erased your Mac with the Apple M1 chip before upgrading to macOS Big Sur 11.0.1, you may not be able to reinstall macOS from macOS Recovery.

A message will appear saying “An error occurred while preparing for the update. Failed to customize software update. Please try again“.

Use an external disk to boot

If you have another Mac and an external drive with flash memory, or another storage device that you don’t mind erasing, you can create and use a bootable installer for macOS Big Sur.

Use Terminal in macOS Recovery

  1. Turn on your Mac and keep pressing and holding the power button until you see the startup options window. Select Options and click Continue.

2. Select the administrator user, click Next and enter the password.

3. When you see the Utilities window, select Utilities> Terminal from the menu bar.

4. Write resetpassword in Terminal, and press Return.

5. Click the Reset Password window to bring it to the front, and then select Recovery Assistant> Erase Mac from the menu bar.

6. Click Erase Mac in the window that opens, and then click Erase Mac again to confirm. When you’re done, your Mac will restart automatically.

7. Choose the language when prompted.

8. If you see an alert that the version of macOS needs to be reinstalled on the selected disk, click macOS Utilities.

9. Your Mac will start to wake up, which requires an Internet connection. When your Mac is activated, click Quit Recovery Utilities.

10. Select Safari in the Utilities window and click Continue.

11. Visit the support article below, by entering this web address in Safari:
https://support.apple.com/kb/HT211983

12. Select the code below and copy it to the clipboard:

cd '/Volumes/Untitled'
mkdir -p private/tmp
cp -R '/Install macOS Big Sur.app' private/tmp
cd 'private/tmp/Install macOS Big Sur.app'
mkdir Contents/SharedSupport
curl -L -o Contents/SharedSupport/SharedSupport.dmg http://swcdn.apple.com/content/downloads/19/41/001-83532-A_LN5NT1FB2Z/o4zodwe2nhyl7dh6cbuokn9deyfgsiqysn/InstallAssistant.pkg

13. Go back to the recovery window by clicking outside the Safari window.

14. Select Utilities> Terminal from the menu bar.

15. Paste the code that you copied in the previous step and press Return.

16. The Mac will begin downloading macOS Big Sur. When you’re done, type this command and hit Return:
./Contents/MacOS/InstallAssistant_springboard

17. The macOS Big Sur installer will open. From this step, you have to follow the onscreen instructions to reinstall macOS, as you normally would.

If Terminal returns “Volume not found”

If Terminal shows a result of “Volume not found” after copying the code above, copy and paste this code and press Return:

cd '/Volumes/Macintosh HD'
mkdir -p private/tmp
cp -R '/Install macOS Big Sur.app' private/tmp
cd 'private/tmp/Install macOS Big Sur.app'
mkdir Contents/SharedSupport
curl -L -o Contents/SharedSupport/SharedSupport.dmg http://swcdn.apple.com/content/downloads/19/41/001-83532-A_LN5NT1FB2Z/o4zodwe2nhyl7dh6cbuokn9deyfgsiqysn/InstallAssistant.pkg