rpi4 on compressed BTRFS root won't boot

[n8henrie]

Hello,

I have a little project at https://github.com/n8henrie/nixos-btrfs-pi that builds an sdImage for a Pi on a compressed BTRFS rootfs. It's been working great on a Pi3 for a while and I recently decided to try to get it working for a Pi4.

It seems like this repo is the recommended way to get much of the hardware support working, but unfortunately when I enable its module I get a non-booting system (it gets stuck at waiting for device /dev/disk/by-label/NIXOS_SD ........).

I'm booting with a custom uboot that I've created via an overlay that enables BTRFS and ZSTD support, I don't know if that is causing the issue?

Perhaps by coincidence, I get the same boot failure (without this module) unless I manually include:

boot.initrd.availableKernelModules = [
        "uas"
        "pcie-brcmstb"
        "reset-raspberrypi"
      ];

but it looks like these are also included in the nixos-hardware module, so that may not be relevant.

Perhaps it's due to setting kernelPackages to pkgs.linuxKernel.packages.linux_rpi4? Manually setting just that option seems to break my config as well.

[n8henrie]

It's not clear what the issue was. A fresh installation with the same boot setup worked without issue; btrfs check revealed warnings: about being "not nodesize aligned" which "may cause problem for 64K page system". I suspect this was from nixos-lustrating from an older Raspbian (that had done the initial mkfs.btrfs steps with an older kernel).

Regardless, doesn't seem to have been an issue with this repo.

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/rpi4-cant-usb-boot-from-btrfs-with-rpi-kernel/28668/2