debian-9.0-ppc64-NETINST-1.iso results in "unknown or corrupt filesystem"

[Dennis Clarke <dc@oetec.com>]

Dear ppc types :

    I have downloaded and booted and installed from the ports area the
following :

    see https://cdimage.debian.org/mirror/cdimage/ports/

    also debian-9.0-ppc64-NETINST-1.iso


I went for the "easy" install and simply allow the installer to put 
everything onto the whole disk in a single partition. Nothing fancy. I 
was also happy to see that it was possible to select packages from the 
ports pkg area :

    host : ftp.ports.debian.org

    subdir : /debian-ports/

Someon on irc suggested that I stay away from the expert install and
just select the obvious simple options. That seems to work out.
Everything went along fine until reboot wherein I see a unknown or 
corrupt filesystem message :

 https://node000.genunix.com/ppc64_deb_sid/20171011_090058_med.jpg

This is followed by all the fans spinning up.  Nothing else.  This is
a PowerMac G5 with 8G of memory and nothing fancy.

Again someone on irc says "that's because you are using Yaboot" which
means the old magic won't work and I need new magic. So a manual setup
of the partitions. So I "need a separate /boot partition" which will
most likely be ext2 or perhaps ext4. However I think, not sure, there
is more to this. There needs to be a disk label ( partitions or slices )
and then one of them must have yaboot which most likely goes looking
for another one which will be "/boot" an ext4 filesystem and then yet
more for the usual filesystems.

So I will try to document this as I flail blindly forwards.

Dennis