Like many others, the only way I was able to get High Sierra running on my Fusion drive was to first install it to a regular HDD and then clone it over to the Fusion drive. This solution was working fine—until I tried to install the Supplemental Update. Once I downloaded the update, I ran into the kernel cache error again.
This time, however, I examined the boot files before and after attempting the update and figured out a solution. I don't know if something like this will work for the initial High Sierra install, but at least it solves the update problem. Here's what I did:
- Attempt to install the update via the App Store like normal. Allow the computer to restart.
- Instead of trying to boot High Sierra (which will fail), boot into Recovery and use the Startup Disk selector to select the macOS 10.13 volume.
- Click the reboot button. (The boot partition will be repaired and Clover should now be able to boot the system normally again.)
- Use
Code:
diskutil mount /dev/diskXsY
in Terminal to mount the Recovery partition, replacing X and Y with the appropriate disk and partition numbers. (Note: I did this while logged into Recovery mode from a different hard drive. A USB installer should also work. I haven't tested it, but I think I could have also done this while booted up normally.)
- Navigate into the Recovery volume and drill down to "com.apple.boot.P/Library/Preferences/SystemConfiguration" (Note: The letter after "boot" may be different on your machine.)
- Open com.apple.Boot.plist and find this line:
- Right below this line, there is a pair of
tags with nothing between them. Enter the following between those tags:
Code:
-rootdmg-ramdisk auth-root-dmg=file:///macOS%20Install%20Data/Locked%20Files/BaseSystem.dmg
- Save the file.
- Reboot and select the usual boot volume in Clover.
Once I did this, the update began to install during the boot routine. The computer rebooted automatically. Once everything was done, I checked the build number in "About this Mac" and confirmed that the update had been applied. The hack I made to the boot file was even removed automatically.
I don't have a setup to test it on, but I wonder if this solution (or something like it) could also be used to solve problems updating from Sierra to High Sierra. In any case, I hope this helps anyone who has run into the same problem as I did. This should avoid the need to start from scratch each time a new update comes out. (At least until Apple gets APFS to work on Fusion drives.)