My Mac Pro was upgraded to High Sierra Awhile ago automatically. I encountered some problems that were difficult to resolve, not sure High Sierra was responsible, but I decided an erase and clean install of High Sierra was warranted, and so I backed up my data and started the procedure. The diskutil only gave me the option to reformat into an APFS format, so I reformatted it in APFS reasoning High Sierra works on it, so it must be the right format after all, right? Big Mistake!
High Sierra then would not install, it would freeze up while trying to install. Internet install also did not work, and it would often freeze and sometimes give sometimes strange and cryptic error codes trying to install. I even tried a USB Boot disk with High Sierra dmg file designed for new install, and it also froze up installing. Trying to go back and reinstall Sierra, as many recommend, well... that’s a problem when you don’t have a working Mac and cannot download it from Apple, and a non-Apple PC won‘t download it from their Mac-only download procedure. So, I made an appointment with the Mac store.
I then came across this post, and while I wasn’t interested so much in rolling it back to Sierra, it gives the critical procedure to reinstall a clean High Sierra with all your data and settings cleared out. Diskutil is unaware that High Sierra only wants to install on a partion with a previous old format (e.g. Macintosh HD), and it doesn’t quite know how to reformat a previously formatted APFS partition back to an older format (High Sierra install converts everything to APFS). The way to address is to DELETE the drive (see original post) in the diskutil. I found pressing Option-Command-P-R just after Power-on would get me to the menu with diskutil. By clicking the small minus sign “-“ next to the drive (+ or - shown) I was able to delete the drive (really it’s the working partition), So, I went ahead and deleted it.
Then, I rebooted again into a recovery mode, I tried Option-Command-P-R method, then diskutil again. Apple says that Diskutil will try to detect the type of storage your are formatting, then shows the appropriate format in the format menu:
How to choose between APFS and Mac OS Extended when formatting a disk for Mac - Apple Support
Hence, if it sees APFS, it will only give APFS format options. But here with the disk deleted, there is no format and thus it cannot detect, and the Apple link above indicates that it defaults to Mac OS Extended which “works with all versions of macOS“. So, after another reboot and Option-Command-P-R after start, diskutil then presents older formats for formatting the disk in the menu, and a major obstacle removed. I then chose “Macintosh HD”. It chose to call the partition “Preboot” by default. I rebooted again, pressed Option-Command-P-R after power on, and then I chose to installed High Sierra. It worked this time. Hurray!!!
Command-R may have worked just as well like the original post from Ethoic showed, but I’m not going through this again to test it. They key here is deletion of the drive in the Diskutil, and also key is the understanding that at least this version of High Sierra (10.13.5) - and possibly others - will install only onto legacy/older storage formats and ironically not on APFS format that it was designed to run on!
A clean install of an OS is a tried-and-true useful and popular option for users to clear out a corrupted OS or sell/give it to others. They should make the procedure less tricky or at least better documented, and it shouldn’t be so easy to tank the entire PC to where most will need the Apple store to recover it.
Thanks for the original poster, I thought I might add to it my specific experience in hopes it might help someone not repeat the 2 days of frustration I went through trying a simple and often useful task.
