Introduction

Did you ever wonder how you can make a clean install on your Mac with High Sierra without being forced to use APFS? Well, I just reinstalled my mac using this method and want to explain how I acomplished this:

Boot from below 10.13

First of all, you’ll need to boot from a Mac OS Version below 10.13 High Sierra. Otherwise you’ll get an error message “Helpertool crashed”. So in my case I booted from a 10.12 Sierra USB stick.

You can now use the Disk Utility of the recovery OS you currently booted from to clean you complete disk. Format the volume HFS+ journaled and choose a simple name without spaces like “internal” (which I used for my internal SSD). Attach the USB stick which contains the High Sierra installer. You can create this installer following these instructions.

Now exit Disk Utility and open a Terminal. Go to the Volume of your attached High Sierra USB Stick.

cd /Volumes/“Install macOS High Sierra”

Start tje omstaööatopm

Start the installation of High Sierra to the freshly formatted HFS+ volume mounted as “internal”. This clean installation will also create the Recovery HD partition.

“Install macOS High Sierra.app”/Contents/Resources/startOsInstall -agreetolicense -converttoapfs NO -volume /Volumes/internal

Read more

More information can be found here. A video of the process and more details are here. If you execute the startOsInstall command with -usage you’ll get a list of available parameters.