Downgrading from Mojave to High Sierra ... lessons learned

[derekw]

Originally Posted by dnanian

I've never heard of Mojave being unable to boot from HFS+ volumes. Can you provide me with the "firmware change" command line they supplied?

Unfortunately I don't have the command line anymore. It was entered while the Mac was in Mojave and now the drive has been erased. Terminal "history" shows nothing.

This article might have related info. https://bombich.com/node/662 FYI, the external drive I used is a Seagate Backup+.

Originally Posted by dnanian

To format back to HFS+, you need to "show all devices" in the View menu, select the drive hardware (above the volume) and then elick Erase. You'll have the choice of Mac OS Extended (Journaled) there. You don't have to use Terminal.

I did not know your method. Apple tech support did not know how to reformat a APFS drive back to HFS+ either. When I googled, I found these results and followed their Terminal commands.
https://wp.me/pmPaT-cco
http://bit.ly/2HXMPNA
https://tek.io/2uCN2xQ

Originally Posted by dnanian

But, you can certainly leave it as HFS+ and restore to APFS. And APFS is certainly what you should be using with internal SSDs in 10.13 or later. You haven't indicated why you don't want APFS...

My Mac mini late-2014 only has hard disk (no SSD, no fusion). It was running High Sierra with HSF+, same for the clone backup. When I restore I did not know if it's safe to restore from a HSF+ clone to a APFS drive. When I asked Apple tech support about this they said I can try but they don't know if it's safe. I saw that SuperDuper "restore all files" function's first step is erase the drive. But I didn't know what format SuperDuper would use after the erase, so I felt safer to erase and format the drive myself to HFS+ in preparation for Superduper's restore.