How do I edit uboot to make sure that I'm disabling and enabling these following

I need help enabling and disabling these following respectively on Kernel level on Ubuntu 18.04, which gives us a base image of Ubuntu


  • Disable Dhcp as bootable source
  • Disable Nvme0 as bootable source
  • Disable Pxe as bootable source
  • Disable Usb0 as bootable source
  • Enable Mmc0 as bootable source
  • Enable Mmc1 as bootable source

I see the following post in the documentation but dint get how go about it

Contains a space-delimited list of storage devices or network protocols that U-Boot scans to find boot scripts.

Valid values include:

•mmc0: the built-in eMMC

•mmc1: the SD card slot

•usb0: any attached USB Mass Storage device

•nvme0: any attached NVMe device

•pxe: network, using DHCP to receive an IP address, then PXE to download a syslinux configuration file

•dhcp: network using DHCP to receive an IP address, then TFTP to download a U-Boot boot script

This variable can specify a subset of the possible values, and even to a single value if the application does not require alternative boot devices.

Ref :