Debian on downstream kernel Part 2
Instructions for running Debian on a Raspberry Pi OS (RpiOS) kernel. See earlier efforts at https://hankb.github.io/MkDocs-blog/tech/Debian_on_downstream_kernel.01/
2025-10-18 Motivation
Trixie is now Stable and RpiOS has migrated to Trixie. This seems like a good time to give this another try. The description below will repeat much of what was done for the previous iteration so for the sake of brevity, it is going into a new note.
Checking https://github.com/raspberrypi/linux the newest stable tag is stable_20250916 and that will be used. The first try will be using Trixie.
2025-10-18 Prep
Pull kernel code and install required build tools.
rm -rf ~/Downloads/pi-kernel/*
mkdir -p ~/Downloads/pi-kernel
cd ~/Downloads/pi-kernel
git clone --depth=1 --branch stable_20250916 https://github.com/raspberrypi/linux
sudo apt install bc bison flex libssl-dev make libc6-dev libncurses5-dev
sudo apt install crossbuild-essential-arm64
Set environment variables
CONFIG_LOCALVERSION="-v8-for-Deb-20250916-X"
KERNEL=kernel_2712
2025-10-18 Build
cd ~/Downloads/pi-kernel/linux
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bcm2712_defconfig
time -p make -j$(nproc) ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- Image modules dtbs
2025-10-19 Copy to target media
Back on olive and with the NVME SSD in the USB enclosure.
Identify the device, in this case /dev/sdb and mount accordingly:
cd ~/Downloads/pi-kernel/linux
mkdir -p mnt/boot
mkdir -p mnt/root
sudo mount /dev/sdb1 mnt/boot
sudo mount /dev/sdb2 mnt/root
sudo mkdir -p mnt/boot/overlays
Install modules to target:
sudo env PATH=$PATH make -j1$(nproc) ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- INSTALL_MOD_PATH=mnt/root modules_install
Install the kernel
sudo cp mnt/boot/$KERNEL.img mnt/boot/$KERNEL-backup.img
sudo cp arch/arm64/boot/Image mnt/boot/$KERNEL.img
sudo cp arch/arm64/boot/dts/broadcom/*.dtb mnt/boot/
sudo cp arch/arm64/boot/dts/overlays/*.dtb* mnt/boot/overlays/
sudo cp arch/arm64/boot/dts/overlays/README mnt/boot/overlays/
Edit the target config.txt to specify the correct kernel (vmlinuz-6.12.48+deb13-arm64) and initrd (initrd.img-6.12.48+deb13-arm64): In this case thee kernel= and initramfs lines were already cvorrect, perhaps because RpiOS and Debian are on the same kernel version.
sudo vim mnt/boot/config.txt # or editor of your choice
Unmount the target device partitions.
sudo umount mnt/boot
sudo umount mnt/root
Install the NVME SSD in the NVME HAT+ on a Pi 5 and power up. No joy. No rainbow screen. It powers up the monitor but the display remains blank.
No boot. Repeating the install and playbooks. Derp. Wrong kernel. New kernel is kernel_2712.img and shows as
root@boson:~# uname -a
Linux boson 6.12.47-v8-16k+ #2 SMP PREEMPT Sun Oct 19 16:53:57 CDT 2025 aarch64 GNU/Linux
root@boson:~#
Which seems odd. I thought the V8 kernel was for the 4B and the 2712 for the Pi 5. Now boot from NVME. Unable to mount root fs .... Boot RpiOS from SD card and add dtparam=pciex1 to config.txt with no benefit. Back to USB/NVME and it boots.
It's not clear to me what to do now. Not booting from NVME is a show stopper for me.