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Details

Add GRUB bootloader patches for talosctl upgrade on RPi5/CM5

Force GRUB instead of sd-boot on arm64 and pass --no-nvram to
  grub-install, working around the SetVariableRT firmware limitation
  that prevents in-place upgrades on RPi5/CM5 hardware.

  Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2026-02-13 19:20:18 -05:00

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Talos CM5 Builder

Custom Talos Linux images for Raspberry Pi 5 / CM5 on Compute Blade hardware.

The official Talos Image Factory does not support CM5 — the mainline kernel lacks CM5 device trees and RP1 driver support. This builder uses the RPi downstream kernel (via talos-rpi5/talos-builder patches) to produce working CM5 images with our extensions and overclock config.

Current versions

Component	Version
Talos Linux
RPi Kernel
iscsi-tools
util-linux-tools

Image tags

Release images are published to docker.io/svrnty/talos-rpi5 with the format:

v<talos>-k<kernel>-<revision>

For example: v1.12.3-k6.12.47-2

Segment	Meaning
`v1.12.3`	Upstream Talos Linux version
`k6.12.47`	RPi downstream kernel version
`2`	Build revision (bumped for config/patch changes on the same upstream versions)

Usage

Install from raw disk image

Download metal-arm64.raw.zst from the latest release and flash to eMMC:

zstd -d metal-arm64.raw.zst -o metal-arm64.raw
# Flash to eMMC/SD via your preferred tool (dd, balenaEtcher, etc.)

Upgrade an existing node

talosctl upgrade --image docker.io/svrnty/talos-rpi5:v1.12.3-k6.12.47-2

Note: In-place upgrades use GRUB with --no-nvram to work around the RPi5/CM5 SetVariableRT firmware limitation. This patch is included but not yet tested in production — re-flashing the disk image is the proven fallback.

# Fallback: re-flash method
zstd -d metal-arm64.raw.zst -o metal-arm64.raw
# Flash to eMMC/SD via your preferred tool

What's included

RPi downstream kernel with CM5/RP1 support (4K page size, aligned with upstream Talos)
GRUB bootloader with --no-nvram for reliable talosctl upgrade on RPi5/CM5
Overclock: 2.6GHz (arm_freq=2600, over_voltage_delta=50000, arm_boost=1)
Extensions: iscsi-tools, util-linux-tools

Known issues

No serial console output after boot

Serial output goes silent after the EFI stub decompresses the kernel and exits boot services. This affects headless debugging on CM5 boards where serial is the primary console.

Upstream: talos-builder#4

Install disk config ignored on SBCs

Talos ignores the machine.install.disk config field on SBC platforms. You must flash the disk image directly to your target disk (eMMC, SD, NVMe). Booting from USB or NVMe also requires flashing directly to that disk — the image targets SD (mmcblk0) by default.

Upstream: talos-builder#22

Roadmap

This project targets production-ready Talos clusters on RPi5/CM5 hardware.

Status	Milestone	Description
Untested	4K page size	Aligned with upstream Talos kernel config. Reduces memory overhead and improves workload compatibility (Longhorn, jemalloc, F2FS, etc.).
Untested	Reliable in-place upgrades	Force GRUB bootloader with `--no-nvram` on arm64 to work around the `SetVariableRT` firmware limitation (talos-builder#21).
Pending	Serial console fix	Debug U-Boot/kernel handoff to restore serial output after EFI stub exit.
Pending	NVMe boot support	Produce images that target NVMe directly, or document a supported NVMe boot flow.

Building

For local builds, CI/CD setup, runner configuration, and project structure, see TECHNICAL.md.

License

This project is licensed under the Mozilla Public License 2.0.

It builds upon the following MPL 2.0 licensed upstream projects:

siderolabs/talos — Talos Linux OS
siderolabs/pkgs — Talos package definitions
talos-rpi5/sbc-raspberrypi5 — Raspberry Pi 5 SBC overlay

Our patches to these projects are in the patches/ directory and are distributed under the same MPL 2.0 terms.

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