Now you can 'attack' the internal fusion drive and get it right. You should be able to log in and get to the finder. IF it's a platter-based drive, it may take longer to boot (depends on the drive, whether it's USB2 or USB3, etc.) The Mac will start from the backup drive. Select the cloned backup and hit return.Ħ. Immediately hold down the option key and KEEP HOLDING IT DOWNĥ. If you have a CCC cloned backup, try BOOTING FROM IT.Ĥ. Your Mac restarts from your Fusion Drive when done.

Choose Reinstall macOS, then follow the onscreen instructions to reinstall the Mac operating system.When Terminal indicates that the operation was successful, quit Terminal to return to the macOS Utilities window.Type Yes (with a capital Y) when prompted, then press Return.Type diskutil resetFusion in the Terminal window, then press Return.When you see the macOS Utilities window, choose Utilities > Terminal from the menu bar.Release the keys when you see the Apple logo or spinning globe.

Turn on your Mac, then immediately press and hold Command-R to start up from macOS Recovery.

Is my BOOTABLE BACKUP safe? Would the Terminal start working on my Backup Drive instead of the Fusion Drive? I afraid to loose it. When I start Mac with plugged to USB a bootable backup external drive by holding COMMAND + R, I will login to Mojave installed on the connected bootable backup drive. When I start Mac by holding COMMAND + R without plugged to USB a bootable backup external drive, the blank starting screen displays only rotating globe and asks to 'Choose Network' from the list of WIFI networks.

which is probably reformatting the Fusion drive. Reading step by step (by Apple support) 'How to fix a split Fusion Drive'.

Get new fusion drive for late 2013 imac