For some reason the update from Sierra to High Sierra on my Mini 2012 went wrong. I know I should have made an update, but I got lazy when everything went fine for three years. So when I got stuck in recovery mode, I was realy stuck. The only install option in recovery mode erases the entire disk. That is not an option, that will delete all my files. I then tried to load Yosemite from a bootable usb drive, hoping I would be able to access my files and save them, so I could do a format and a clean install. No joy, Yosemite will not load on the Mini. It will not start the installation at all. I then decided to put Linux Mint on the drive, so I could at least recover my data. Mint installed like it was supposed to and I could see all my folders. I just could not get into them, because I have no rights to access the userfiles in OSX with a Linux account. I then tried to clone the drive. Cloning went great, unfortunately I wasn't able to access the folders in the clone either. I then changed the hard disk in my Mini for another one. Using Internet recovery I expected to get a clean install of El Capitan, because that is the OS the Mini came with. In stead, internet recovery tried to install High Sierra on my new drive. It could not do that because that drive has not been formatted in GUID format. The message box said I should format the drive in GUID format using Disk Utility. Unfortunately, there is no way to get back to the option screen from this point, when you can not accept the terms of installation you can not go back. So another 20 minutes passed while Internet Recovery loaded for the third time. When I accessed Disk Utility there was no option to format my new drive in GUID format, only standard Apple formating, ExFAT and DOS. I tried all options, none of them resulted in a drive formatted in a way High Sierra would install on. Changing the hard drive in a Mini isn't something I would like to do more often, I just want a working OSX version on the drive that is in there. I can then put the original drive in an external enclosure and access the files using my usual username. I think I have tried anything, it just won't work. Why does a company that thinks of everything when designing a phone case forget to include a roll back option in an upgrade procedure? I am open for suggestions, how do you get an OS that has been upgraded to the point of nonfunctionality working?