Booting FreeBSD on BeagleBone Black from microSD by default

[Bernd Walter]

On Tue, Apr 12, 2016 at 08:19:30AM -0600, Ian Lepore wrote:
> On Mon, 2016-04-11 at 06:33 -0700, Tim Kientzle wrote:
> > > On Apr 10, 2016, at 9:06 PM, Hal Murray <hmurray at megapathdsl.net>
> > > wrote:
> > > 
> > > 
> > > Does anybody have the recipe for setting things up so that power on
> > > boots 
> > > from the microSD card without holding down the button?
> > 
> > If the ROM cannot boot from eMMC, it will try to boot from microSD.
> > 
> > The easiest way to make the eMMC not bootable is to zero out the
> > boot sectors using dd:
> > 
> >      dd if=/dev/zero of=<eMMC device> count=100
> > 
> > Of course, this makes the eMMC entirely unusable.  I think you
> > can then reformat the eMMC (make sure it does not have a FAT
> > partition and does not have boot blocks) so it can be used without
> > the ROM trying to boot from it.
> > 
> > This way, the ROM will load U-Boot from microSD.
> > 
> > > 
> > > I'm pretty sure it will be simple after I know how to do it. 
> > >  Google found info on the idea, but I couldn't find the file that
> > > needs editing.  It's off in uBoot land.
> > 
> > Even if the ROM loads U-Boot from eMMC, the default Linux
> > U-Boot setup on the eMMC can be configured to then load
> > the Linux kernel from microSD.
> > 
> > If you install the FreeBSD version of U-Boot to eMMC, you might be
> > able to
> > do the same thing.  Personally, I find the recipe above much
> > simpler.
> > 
> > Cheers,
> > 
> > Tim
> 
> No need to zero out the onboard emmc or mess with its too-complicated
> linux-centric env vars...  The AM335x ROM boot code loads u-boot from
> the first FAT partition it finds with the active/bootable flag set. 
>  Normally that's the emmc, but you can turn it off and then it'll look
> for a partition on the external sdcard.  Once you've booted to freebsd
> normally, do
> 
>   gpart unset -a active -i 1 mmcsd1
> 
> And now it will boot from the sdcard unless you turn the active flag
> back on on the emmc.

Good to know - that's so much better than erasing the old content,

-- 
B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.