macOS Catalina Bootloop Dance

I stupidly forgot to turn off automatic macOS updates on my home iMac. When I got back from a business trip last night I found my partner almost in tears and the iMac endlessly replaying the kernel panic screen after a failed macOS Catalina update.

Safe mode had the same kernel panic so I dropped the iMac into Recovery mode with a Command + R startup, but the weird thing was that once iMac was in Recovery mode Bluetooth stopped working. Magic Keyboard and Magic Mouse 2 weren’t magic anymore but frustratingly useless appendages. The cursor was tantalizingly close to ‘Restore from Time Machine Backup’ but all I could do was look at it.

I wasted hours creating a bootable macOS Catalina install USB stick and testing it, but the same Bluetooth bug happened again and again. Today’s chore is finding a tossed off USB mouse and keyboard to finally get the iMac on the road to recovery.

I checked online and sure enough there were Catalina update bootloop failures with dead Bluetooth complaints on Japanese websites, a few mentions on English language sites too. If this is ever mentioned by Apple I’m sure it will be passed off as, ‘a select few users experienced blah blah issue with blah blah Macs.’

How nice it is to be one the select few.

10/11 UPDATE: Some Catalina upgrade bootloop-ers report restoring the previous system from a Time Machine backup then doing the Catalina upgrade again works. Instead of that I went straight to: boot with macOS Catalina install USB, wipe hard disk, do clean install, restore from Time Machine backup. Wiping the iMac APFS formatted Fusion drive was a little weird, Catalina APFS creates 2 APFS containers: Mac HD (visible) and Mac HD Data (invisible) that had to be deleted separately, then a single new container created (Howard Oakley has a great explanation of macOS Catalina APFS if you are interested). It all worked out but the time investment was high: at least 12 hours down the drain from setup to babysitting the process.

10/17 UPDATE: the macOS Catalina Supplemental Update (what a lame name) is out and supposedly fixes the bootloop issue, which in my case seems related to not enough free disk space.

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