MacBook Pro 2019 Upgrade to Big Sur left me stuck in a boot loop

my MacBook Pro doesn’t start cleanly after Big Sur.

Here are the details:

• I have a MBP 2019 (T2 Chip)

• I erased the Macintosh HD

• I didn't backup the disk.

• I un-linked the Apple ID from the MBP (because of the error 1008F in Internet Recovery)

• I didn't unlock the bootable USB.

• When Internet recovery tries to install macOS (Catalina or Mojave) the installation fails.

• I had the Big Sur Beta installed.

I erased the disk and tried to reinstall the OS. Catalina's setup starts, and at 95% (approx.) it resets and starts the Internet Recovery again. Mojave installs and at the Apple logo during boot, it shows a bar, but after 1 second it restarts and if I don’t go to the Internet Recovery it continues in a boot loop.

I'm trying to get my Mac back functional, am I forgetting to do something critical?

Solution 1:

Given that you can get to 95% of the install, I'm going on the assumption that you don't have a firmware password nor FileVault enabled.

First thing I would do is go a step further with the erasure of the disk. More than likely, you've got APFS containers set up and if one of the volumes is corrupt and you're not properly removing it (via the format), this boot loop could be a symptom. So, let's wipe it clean and put a plain macOS file system on it (not APFS). When you boot into Recovery, launch Terminal and type the following command:

$ diskutil JHFS+ "Macintosh HD" disk0

Normally on a MacBook laptop, the internal drive is disk0, but to be completely certain, you can do a diskutil list and look for the "internal" drive, similar to what's below:

/dev/disk0 (internal, physical):

Next, once you've done that, reboot your Mac, again into Recovery. You likely don't have to reboot, but let's start nice and clean. As for operating systems, you should be able to install Catalina, but if you run into issues, try installing Mojave.

When you go to erase the disk this time using the GUI version of Disk Utility, erase it again, but this time use APFS format so it can create the necessary volumes in the container. Then proceed with the install.

This should "get you back to back to zero" - a phrase that means back to where you started. When you go to install Big Sur, get an external USB 3 drive. It doesn't have to be large - 64GB should be fine, but I recommend USB 3 for the speed. Don't install Big Sur (or any beta OS for that matter) on your "work machine." If things go sideways, like they did here, you'll have trouble getting back. By installing and booting from a USB drive, you can easily revert back to your original macOS.