Follow Apple’s instructions for a clean re-install, and you’ll probably hit an error, and be left floundering in Recovery mode with an unbootable system.
recovery mode
Do you know how to customise the zsh shell now standard in Catalina? Here’s an excellent book which covers it in detail – and curious choice in 10.15.
Diagnostic, Recovery, Safe, Startup Manager, Verbose, reset SMC/NVRAM, firmware restore, Target Disk/Display, Single-User (SUM) in outline.
Don’t just hold Command-R and hope that you’ll install the right version of macOS. Here’s structured decision-making to save you time.
Single-user mode to run fsck to check and repair your boot disk became tricky with Fusion Drives. With a T2 chip, it’s not practical in its traditional form.
Had my Mac frozen, or was it just very busy running tests on the boot disk? When I forced it to restart, what did the log reveal?
Mojave brings new flying thumbnails of screenshots and more options. But do they solve limitations in taking screenshots?
How to prepare your Mac to pass on to a close relative, a purchaser, or even for recycling.
So you’ve just got your new MacBook Air, MacBook Pro, or Mac mini – or iMac Pro – with its T2 chip. How does that change things? Practical advice and solutions.
Like El Capitan before it, Sierra has now vanished from the App Store. It has also been removed from your Purchased list. How can you install it now?
The Eclectic Light Company 