Those are exactly the same instructions I've been following, that have left me with a failure notice ("No disk found," or something like that) at step 21 over and over again. Do I still use the same initrd.gz (18,488,794 B, 09/21/2015)?
OK, there is one instruction I wasn't following to the letter; I was trying with kernel 4.1 and 4.3. I hope my next try, with 4.2, will do the trick.
Later: I downloaded a new copy of initrd.gz. It was slightly shorter (18,453,666 bytes) than the one I had been using. And I used kernel 4.2. And once again, I "Continue" at step 21 and get "... The failing step is: Detect disks"!
Any decent program should easily find two disks on my system. One spins around -- /dev/sda. To be sure, much of it is full of Amiga partitions, but it has 486 GB of free space on it that should be easy to detect (Disk Utility has no trouble).
The other is solid state. /dev/sdb1 is where Ubuntu 12.04 LTS resides (along with a not-quite-working chroot-wily) in 157 GB. Formatted and waiting for an install of Ubuntu is 105 GB of /dev/sdb2, and there remains 238 GB free on that UNDETECTED disk.
Why can't initrd.gz find something? FRUSTRATING!