I am working on a RPI 3. Operating system is Archarm.

I tried a suggestion to add arm_control=0x200 in /boot/config.txt for my RPI 3. So, it was expected to run in Armv8 mode. However, after rebooting RPI, the system stuck almost immediately in the "Rainbowscreen".

You can imagine that I was not able to access /boot/config.txt to strip out the ARMv8 mode line.

To fix the problem I tried to mount the sd card in my computer. However there is no config.txt on the first partition!

Any ideas to access /boot/config.txt apart from a complete renstall of the operating system?

  • I am assuming your computer is a windows box. Have you tried a live CD. However, usually the boot partition is a FAT partition which you can read from a PC, Linux and even Mac IIRC. Sep 1, 2016 at 19:52
  • My pc has ArchLinux as OS, not windows. I tried as root mount /dev/sdb1 /home/user/sd. Only showing directories "grub" "lost+found", "memtest86+" and "syslinux" and initram images.
    – kzpm
    Sep 1, 2016 at 20:04

1 Answer 1


Simple solution: there was another partition /dev/sdb2 that contained /boot/config.txt. So I was able to remove the arm_control=0x200 line.

Flawless boot!


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