Create an image for boot from USB stick

[JMStranz]

I have successfully built the image "rpi-test-image" and booted my "Raspbery Pi 4" from the SD card.

However, you cannot use this image to boot from a USB stick. In the file "cmdline.txt" (partition "boot") the SD card is fixed for the parameter "root":

root=/dev/mmcblk0p2

How can I create an image to boot from a USB stick?

Jan.

[agherzan]

You should play with CMDLINE_ROOTFS. With that you would be able to set anything for that part of the arguments.

[JMStranz]

Thanks for the tip!

However, I have already tried to adjust the command line for the Linux kernel as follows.

Assuming that for the USB stick the device /dev/sda is created, the rootfs partition is /dev/sda2.

I have adjusted the line in the file "cmdline.txt" accordingly:

... root=/dev/sda2 ....

However, the RPI4 still does not boot from the USB stick.

If I copy the same image (file "cmdline.txt" of course unchanged) with "bmaptool" to a SD card, then the RPI4 boots successfully.

Is a manual, subsequent change in the file "cmdline.txt" not sufficient?

[agherzan]

Are you using uboot?

[JMStranz]

Regarding U-Boot and Linux Kernel the following variables are set in my machine configuration:

RPI_USE_U_BOOT = "1"

UBOOT_MACHINE = "rpi_4_config"

KERNEL_BOOTCMD ?= "booti"

RPI_KERNEL_DEVICETREE = " \ broadcom/bcm2711-rpi-4-b.dtb \ "

VC4DTBO ?= "vc4-fkms-v3d"

ARMSTUB ?= "armstub8-gic.bin"

SDIMG_KERNELIMAGE ?= "kernel8.img"

KERNEL_IMAGETYPE_UBOOT ?= "Image"

KERNEL_IMAGETYPE_DIRECT ?= "Image"

I've attached my machine configuration "rpi4-64.conf" as "rpi4-64.txt" rpi4-64.txt

By the way: for "meta-taspberrypi" there are 2 sources:

https://github.com/agherzan/meta-raspberrypi.git https://git.yoctoproject.org/meta-raspberrypi

Which GIT repository should I use?

[EasyIP2023]

@JMStranz Can you see the usb drive in u-boot console? May find this link useful

• https://wiki.analog.com/resources/tools-software/linuxdsp/docs/das-u-boot/loading_file_from_usb_storage_in_uboot

Although not u-boot this is how I boot a live usb image for x64 AMD machine with grub. You may need to create an initrd put that on the usb drive then instruct u-boot to boot off usb drive's initrd image + device tree.

menuentry 'Initrd Image' {
    linux /bzImage LABEL=root root=/dev/ram0 console=tty1 console=ttyS0,115200n8 rootfstype=ext4
    initrd /initrd
}

Yocto wise to build initrd just need to set these two variables

INITRAMFS_IMAGE ?= "<image recipe name>"
INITRAMFS_IMAGE_BUNDLE ?= "0"

EDIT I also add

IMAGE_BOOT_FILES:append = "\
    ${ROOTFS};rootfs.img \
    ${INITRAMFS_IMAGE}-${MACHINE}.cpio.gz;initrd \
    "

[JMStranz]

Since I am still using the older branch "dunfell", I need to set the variable "CMDLINE" in my "local.conf" file. E.g. for booting from a USB stick:

CMDLINE = "dwc_otg.lpm_enable=0 ${SERIAL} root=/dev/sda2 rootfstype=ext4 rootwait"

The possibility to set the variable "CMDLINE_ROOTFS" is only available in one of the newer branches of "meta-raspberrypi".

[agherzan]

@JMStranz The yocto project one is a mirror of the Gihub project. So this means that it doesn't matter which one you are using.

So the answer is yes, you are using uboot. Check the scr file: https://github.com/agherzan/meta-raspberrypi/blob/acb2f73e58c5a2e105e416c5e8a609c493193005/recipes-bsp/rpi-u-boot-scr/files/boot.cmd.in