UEFI installation

[Greg Troxel <gdt%lexort.com@localhost>]

(I have a new 2019 Dell, and I'll post details in the thread where I
asked about hardware after it is working.)

Windows is set up to boot gpt/UEFI on the 1T low-end SSD that I have set
aside.  I'm thus trying to install onto a new 4T SSD.

The BIOS situation is a little funky.  It's clearly UEFI, but it has a
"legacy option rom" setting that seems to allow for booting via USB in
which case it would use MBR.  One seems to need to put the bios in that
mode for USB and then back to normal for UEFI boot from internal disk --
but I'm really not sure.

I am installing netbsd-9 (because the system I am migrating is netbsd-9
and I am trying to do as little as possible in one step).   The
installer boots, and I did a gpt install.

Flipping back to internal/UEFI boot, it failed to boot, and with the
install image utility menu I see that it is gpt, but there is no EFI
partition which explains it.

So it seems the installer detected that it booted from mbr instead of
UEFI and set up MBR probably gptboot and skipped the EFI gpt partition.
Maybe I'm over-assuming.

I am therefore thinking that either:

  I need to coax the BIOS into booting UEFI from USB (or maybe boot an
  install CD)

  I need to tell the installer that I want a UEFI install

  I need to break into utility menu and make the EFI partition myself

and would appreciate clues from those who have gone down this road
before.  (I have been sufficiently retro that I have rarely dealt with
UEFI.)

For the EFI partition, what are the rules?  It seems like

  it's first

  it's maybe aligned to ?

  the size is at least X and less than Y

  it contains bootx64.efi (and maybe bootia32.efi, but is that necessary
  on a post-2010 CPU?)

and making it match what windows did seems safe enough

This page seems out of date as the install image names are different now
(on netbsd-9): 

  https://wiki.netbsd.org/Installation_on_UEFI_systems/