Troubleshooting and FAQ

Troubleshooting tips and FAQ

Modifications from Standard Raspberry PI OS Lite

The SCM ships with a pre-installed version of either Raspberry PI OS Lite (bullseye 64bit) or Ubuntu Server 22.04 (jammy) with a more secure configuration.


The pre-installed image is encrypted and cannot be replaced via rpiboot. Once Bootware is installed, Bootware can install new images based off Bullseye or Jammy in the Zymbit zi image format. See the Getting Started section and the zb-update tool.

Important: The CM4/SCM firmware must include bootloader version 2023/01/11 or later in order to work with Ubuntu 22.04. The version can be verified with the vcgencmd bootloader_version command. The firmware is not field upgradeable. If you have a CM4/SCM with an earlier version of the bootloader and need to run Ubuntu 22.04, please contact


  • HTTPS endpoints are limited to a zi image of approximately 6GB. The zi images are compressed, so this is not normally a limitation with A/B configurations. If you have zi imagest larger tha 6MB, download the image to a local device with 3x the image size space and use the local device endpoint.

  • Important boot files to not delete.

    • Boot.scr
    • zboot.enc
    • u-boot.bin
    • config.txt
    • [After bootware update] usr-kernel.enc
    • [Before bootware] cmdline.txt
    • [Before bootware] kernel8.img for rpiOS and vmlinuz for ubuntu
  • The /boot filesystem should be partitioned for 512MB of space or more. Our default configuration as shipped uses a /boot partition of 512MB. Ubuntu in particular creates backups of all files on updates that may exceed free space with Bootware.

  • Turn off unattended-upgrades. /boot/firmware/boot.scr in ubuntu gets replaced by updates from apt and other services. This will brick the device if its booted on the ubuntu made boot.scr. Ubuntu does not use u-boot on the Pi but writes over boot.scr. If ever doing a kernel update/upgrade, you must cp boot.scr.bak boot.scr prior to rebooting.

  • In config.txt, otg_mode=1 can’t be set. DWC2 needs to be enabled. This is set at our factory and by bootware (and is the default with ubuntu), but if changed, the system will not boot.

  • Non Bootware: Ubuntu requires the initrd.img on their system to boot up. Be wary of replacing this file or removing it

  • Be cautious around the policies set in the supervised boot and the files put in the manifest. This follows hardware not images. This also applies to the other tamper policies.

Changes to our standard images

The table below summarizes changes made to the standard image.

DefaultAs Shipped
Boot partition of 256MB2x Boot partition size - 512MB
Console login allowedDisabled
SSH optionally enabledSSH with password allowed
Hostname is raspberrypiHostname changed to zymbit-dev
Default user of piDefault user is zymbit. User pi removed. Passwd set to zymbit