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

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..