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Running Yocto Project image

Boot sequence fails with "Failed to mount /uboot" and "codepage cp437 not found"

This sometimes happens when using one of the minimal images from the Yocto Project, such as core-image-minimal or core-image-full-cmdline. These images do not include the kernel-modules package, which contains the kernel module with codepage 437. There are two ways this can be resolved:

  • If you're compiling a custom kernel, it is recommended to set the kernel configuration option:


    Please refer to the Yocto Project Manual for how to use menuconfig to generate and save defconfig files for the kernel.

  • If you're not building a custom kernel, you can add this line to your local.conf in order to include all the kernel modules in the image:

    IMAGE_INSTALL_append = " kernel-modules"

    This is an easier fix, but also requires more space in the image than the previous solution, since all modules will be included, not just the missing one.

System stops at U-Boot prompt

There are reports of some systems having trouble running the U-Boot boot commands and getting stuck at the U-Boot prompt. This has, notably, been reported to happen on the Raspberry Pi family of boards with certain serial port adapters. In the failing scenario, it is believed that the serial port adapter is electrically noisy resulting in spurious data on the console that is interpreted by U-Boot as the user intentionally interrupting the boot process. It is unclear which brands of serial port adapters cause this issue or if certain boards are more susceptible than others.

If you are experiencing this issue, there are several proposed workarounds that you should try:

  • Disable the serial console by editing config.txt. With Yocto builds you can set the following in your local.conf to disable this:

    ENABLE_UART = "0"
  • Change the U-Boot configuration to disable the UART for console input. Adding the following to the U-Boot environment has been reported to address this in some situations:

    setenv stdout lcd
    setenv stderr lcd
    setenv stdin usbkbd
  • Modify the U-Boot code to require a different key sequence to interrupt the boot. Some tweaking of the following settings in the U-Boot code may help here:

      "\nRPi - booting... stop with ENTER\n"

I moved from an older meta-mender branch to the thud branch and suddenly my image is just a few MiB too small

This is a typical symptom:

error: update (952107008 bytes) is larger than the size of device /dev/mmcblk0p3 (947912704 bytes)

This is because of an optimization to the thud branch which uses more of the available space in the sdimg and uefiimg images. However, it also means that if the device was provisioned with an older image, the new update will be just slightly too big for the old partition to hold it.

To revert to the old size calculation, add this to your build configuration (machine.conf or local.conf are good places):

MENDER_PARTITIONING_OVERHEAD_KB = "${@eval('(int((${MENDER_PARTITION_ALIGNMENT} - 1) / 1024) + 1) * 4')}"