quoted

- Can it be renamed to md0?

Sure.
If this is being assembled by the initrd, then either the initrd must set the
hostname to "fileserver" before mdadm gets to assemble the array, or the
initrd must contain an /etc/mdadm.conf which lists "/dev/md0" has having the
UUID of this array.

NeilBrown

I'm learning a few things the hard way here e.g. I had saved my
mdadm.conf to a file in the home folder of the default user so I could
reference it later if needs be - no flash, no file.  Next time email
it to myself.

If I were to run sudo update-initramfs -u would that restore things or
pretty much make md127 permanent.

In the event update-initramfs -u is not the way to go, it there an
example of a good mdadm.conf floating about that I can reference to
make the necessary changes?