A video of the process and more details are here.

вЂћInstall macOS High Sierra.appвЂњ/Contents/Resources/startOsInstall вЂ“agreetolicense вЂ“converttoapfs NO вЂ“volume /Volumes/internal Easiest way to Clean install macOS without usb DriveAs usual Apple no longer supply bootable USB Flash Drive or macOS CD Disk Using this tutorial you will be. This clean installation will also create the Recovery HD partition. Start the installation of High Sierra to the freshly formatted HFS+ volume mounted as вЂћinternalвЂњ. I used a thing called DiskMakerX7 to create a bootable 16GB USB drive named 'Mac OS High Sierra Install Disk' It seemed to boot OK, so I selected 'Install MacOS' Now, when I boot the iMac (usb not inserted), all I get is a 4-choice menu: Restore a Time Machine Backup, Install MacOS, Get Help, and Disk Utility. Go to the Volume of your attached High Sierra USB Stick. that are much quicker resolved with a clean installation of the OS. Now exit Disk Utility and open a Terminal. Well, to reinstall macOS Sierra without losing data, you can do it manually or you. You can create this installer following these instructions. Release the Command + R key combination once you see the Apple logo on display. Restart your Mac, or power it on, while holding down the Command + R key combination.

Attach the USB stick which contains the High Sierra installer. Clean Install macOS / OS X Over the Air, Completely Untethered - All You Need is an Internet Connection. Format the volume HFS+ journaled and choose a simple name without spaces like вЂћinternalвЂњ (which I used for my internal SSD). You can now use the Disk Utility of the recovery OS you currently booted from to clean you complete disk. So in my case I booted from a 10.12 Sierra USB stick. 2: Make a Bootable USB MacOS High Sierra. Here itвЂ™s time to set up and performing a clean installation of macOS Sierra. Remember that performing a clean install erases everything on the Mac. Now in the previous steps, if you have installed macOS Sierra from the USB Installer to the partition that you created for macOS Sierra 10.12, then after booting from that partition that macOS Sierra is installed on it. Otherwise youвЂ™ll get an error message вЂћHelpertool crashedвЂњ. Perform a clean Installation of macOS Sierra. 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:ДЇirst of all, youвЂ™ll need to boot from a Mac OS Version below 10.13 High Sierra.

Clean install mac os sierra without usb