First of all, I need to express my anger about the latest Apple developments. The story starts with a broken keyboard in a 2017 MacBook Pro. Apple will replace the keyboard without costs, but they will take it for two to four weeks. So, I found one of my old MacBooks (2011) will do an excellent job for this time. Only, there was MacOS Sierra, not even High Sierra installed. And with Sierra, I can’t run all of the application I use on my 2017 MacBook. Ok, I started to update to at least High Sierra which crashed in the middle of it because of a power outage. And then, and then, the Mac didn’t find any hard disks anymore.
Sure, I was shocked! But wait!
I have a 2011 MacMini running on an external 256GB SSD. I took this SSD and booted the MacBook (holding Alt while powering on) with it. The disk utils can find the built-in SSD but no filesystem on it. Ok, I thought, I will have to install the OS first and then use my Timemachine-backup and restore my data. Usually, it will take a day until I’ll be back to normal operations. Boring. But wait again! I installed High Sierra to the internal SSD of the MacBook, booted, and, surprise, surprise, back to normal with all my data. Even stored passwords and licenses worked!!! So cool!
Here is my advise
Buy an external disk and install the OS you’re currently using from the hardware you now on onto this external drive. Try to boot your machine from this external disk. Keep this disc in combination to your Timemachine-backups. It can help a lot, just in case.