| I am a little curious as to how my NetBSD rootfs at GPT
| partition 4 is called hd0d by the booter
Is it? You shouldn't care, don't use those kinds of names when
booting from GPT. Instead use the NAME=label syntax (but beware,
for NetBSD currently, the total length of the "NAME=label" for the
root/boot filesystem (and only that one) is 16 bytes (I think 15 useful
ones, plus a \0). Since "NAME=" consumes 5 of those, the label for
the NetBSD root filesystem needs to be 10 bytes, or less (labels are
actually UTF-8 strings (except for in the GPT label itself, where they are
UCS-2 (more or less UTF-16) but that's of no concern to almost anything),
so one character, if it isn't ascii, can use 2 3 or 4 bytes).
When using gpt, there is no concept at all of the "whole device" when
referring to partitions, GPT partitions are not allowed to overlap each
other (unlike disklabel partitions), so you cannot have a partition, and
something such as the "whole device", as they would have blocks in common