Knowing the difference helps you work out what to do in response, and how to work out what went wrong.
startup
Diagnostic, Recovery, Safe, Startup Manager, Verbose, reset SMC/NVRAM, firmware restore, Target Disk/Display, Single-User (SUM) in outline.
Why do Macs with T2 chips show a black screen when starting up or updating their firmware, and why so long that it’s scary?
Disk integrity checks appear to have been dropped from Safe Boot. OpenDirectory databases are rebuilt. With a full listing of all blocked extensions.
Some important similarities, such as the entry marking the beginning of startup, but plenty of changes in APFS and security entries.
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.
Extensive listing of places to find key information such as your User UUID/GUID, Ethernet MAC, model identifier, and much more.
What are the benefits to leaving your Mac running all the time? And the costs? Which should you choose to do?
A new version of Mojave brings some fixes, and introduces some new bugs. Here a few for starters. I’ll add more as we discover them.
The Eclectic Light Company 