Booting from USB on RPi3

[bob prohaska]

On Tue, Apr 21, 2020 at 10:32:03AM +1200, Jonathan Chen wrote:
> On Tue, 21 Apr 2020 at 10:30, Jonathan Chen <jonc at chen.org.nz> wrote:
> [...]
> > > Where is the kernel loading from? I gather it's been long-time
> > > practice to load the kernel from microSD and then mount the USB
> > > device as root; it that what you're doing? It appears that using
> > > usbboot (correctly!) would eliminate that extra step.
> >
> > The kernel loads from the external USB drive. The only thing on the
> > microSD card is the renamed loader.efi and the loader.env file.
> 
> And the u-boot, of course.

You're doing what I'd like to accomplish. However, I take it the
chain of events is that the Pi's GPU starts u-boot on the microSD,
that starts FreeBSD's loader on the microSD card then FreeBSD's 
loader acceses the USB drive. I gather there is no bootable FAT32 
partition on the USB drive. 

Have I got that right?

Thank you!

bob prohaska