Mac OS Boot Troubleshooting
I found this link and article about getting help when your Mac won’t boot. It turns out there’s secret keystrokes you an use
> > > > This guide is for troubleshooting macOS in the scenario that it can’t boot up. > > > >
I have personally encountered a couple of times, frightening scenarios, where my mac somehow could not boot up, or get stuck during login etc. macOS provides many “secret” modes to help to troubleshoot.
Knowing them will be handy in time of crisis.
You will need to hold down certain keys when your machine is powered on to enter these modes. When you hear the startup sound and see the Apple logo, you may release the keys.