Modifying the BBB boot so that it doesnt boot from the microSD when inserted

[Luther Goh Lu Feng]

I understand that even though BBB boots from the eMMC first, if a bootable microSD is inserted, it will boot from the microSD[1]. I believe uboot is responsible for this behaviour and would like modify uboot. 

- How would I go about doing it? 
- Is it a matter of modifying uEnv.txt or a recompilation of uBoot?
- If it is the earlier, then what is the path of uEnv.txt? Is it /uEnv.txt or /boot/uEnv.txt[2]?


[1] https://groups.google.com/d/msg/beagleboard/laUYQg80MZg/PuOY_Lt9CgAJ
[2] http://cholla.mmto.org/bbb/network_boot.html 

[Robert Nelson]

On Mon, Oct 9, 2017 at 3:18 AM, 'Luther Goh Lu Feng' via BeagleBoard
<beagl...@googlegroups.com> wrote:
> I understand that even though BBB boots from the eMMC first, if a bootable
> microSD is inserted, it will boot from the microSD[1]. I believe uboot is
> responsible for this behaviour and would like modify uboot.
>
> - How would I go about doing it?
> - Is it a matter of modifying uEnv.txt or a recompilation of uBoot?
> - If it is the earlier, then what is the path of uEnv.txt? Is it /uEnv.txt
> or /boot/uEnv.txt[2]?

BootRom, "boot" order:

1: eMMC
2: microSD

U-Boot, "scan" order:

Scan microSD for:

1: /uEnv.txt
2: /boot/uEnv.txt

Scan eMMC for:

3: /uEnv.txt
4: /boot/uEnv.txt

So.. don't have either /uEnv.txt or /boot/uEnv.txt in your microSD..

Regards,

--
Robert Nelson
https://rcn-ee.com/