Is there any place that debugging messages get logged during the start4.elf portion of the boot process?

BEFORE start4.elf runs, when the EEPROM is running, it's possible to configure UART output. This is useful to confirm the the EEPROM-portion of the firmware was able to read the sd card and locate start4.elf.

AFTER the kernel has started to boot, messages should be logged in /var/log/messages by the kernel.

However, I'm hitting issues where the EEPROM bootloader finds and starts start4.elf, but then the boot process stops working at some point before the kernel starts logging messages.

[This question is asked in the context of the Raspberry Pi 4].

  • Did you solve this was it one more bricked unit?
    – Simson
    May 27, 2020 at 1:53
  • it the kernel start it should be able to continue print to the uart but this is what we do not see?
    – Simson
    May 27, 2020 at 1:54
  • I re-created the boot image; that seemed to resolve my issue (if my memory serves correctly). Oct 1, 2020 at 17:23

1 Answer 1


In the config on the first partition of your SD card you can set two variables:


That should make start.elf print its own debug to the uart.

For the kernel add

console=tty0 console=ttyS0,115200

so it will print to both the graphical console and UART.

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