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: v1.12.4-k6.12.47-4

Segment	Meaning
v1.12.4	Upstream Talos Linux version
k6.12.47	RPi downstream kernel version
3	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:v1.12.4-k6.12.47-4 --nodes <node-ip>

In-place upgrades are fully supported. The image includes patches to force GRUB with --no-nvram on arm64 (working around the RPi5/CM5 SetVariableRT firmware limitation) and to handle the SBC EFI-only disk layout (no separate BOOT partition).

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
• SBC EFI-only boot layout support (probe, install, revert all fall back to EFI partition when BOOT partition is absent)
• Fallback to classic bind mounts on kernels without open_tree support (Linux <6.15)
• Overclock: 2.6GHz (arm_freq=2600, over_voltage_delta=50000, arm_boost=1)
• PCIe Gen 3 enabled for NVMe (~800 MB/s, via dtparam=pciex1_gen=3 in config.txt)
• Serial console on GPIO UART0 (dtoverlay=uart0-pi5, 115200 baud, even parity)
• Extensions: iscsi-tools, util-linux-tools

Known issues

Serial console (read-only)

The serial console outputs kernel logs, boot messages, and panic traces over GPIO UART0 (ttyAMA0) at 115200 baud with even parity. Talos Linux has no interactive shell — the console is read-only and cannot accept input.

On Pi5/CM5, GPIO 14/15 are not mapped to UART by default (unlike Pi4). The dtoverlay=uart0-pi5 device tree overlay is required and is applied via configTxtAppend (after disable-bt and disable-wifi — ordering matters).

Wiring (Compute Blade)

Connect a 3.3V USB-to-UART adapter to the front UART header (3-pin: GND, RX, TX). Only two wires are needed for read-only monitoring:

  USB-UART Adapter          Compute Blade (Front UART)
  ┌──────────────┐          ┌──────────────┐
  │          GND ├──────────┤ GND          │
  │           RX ├──────────┤ TX           │
  │           TX │          │ RX           │
  └──────────────┘          └──────────────┘
      3.3V logic              3.3V GPIO

• Adapter RX connects to Blade TX (adapter receives data from the blade)
• GND to GND (common ground reference)
• Adapter TX is not needed for read-only monitoring (Talos has no shell to send input to)

Warning: CM5 GPIO is 3.3V only. A 5V logic adapter will crash or damage the board.

Tested with: USB to TTL Serial Cable (FT232RNL) set to 3.3V mode.

Reading the console

# macOS — use screen with even parity
screen /dev/cu.usbserial-XXXXXXXX 115200,,cse

# Linux — configure with stty, then read with cat
stty -F /dev/ttyUSB0 115200 cs8 parenb -parodd
cat /dev/ttyUSB0

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). For NVMe boot, dd the metal image to the NVMe drive and configure the EEPROM boot order (BOOT_ORDER=0xf416, PCIE_PROBE=1).

Upstream: talos-builder#22

Patches

Patch	Target	Description
0001 (pkgs)	Kernel	RPi downstream kernel 6.12.x with CM5/RP1 device tree and driver support
0001 (talos)	Modules	arm64 kernel module list for RPi downstream kernel
0002 (talos)	GRUB	--no-nvram for grub-install on arm64 (U-Boot lacks EFI SetVariable)
0003 (talos)	Bootloader	Force GRUB over sd-boot on arm64 (sd-boot crashes without EFI runtime)
0004 (talos)	Runtime	Fallback to classic bind mounts on kernels without open_tree (Linux <6.15)
0005 (talos)	GRUB	Handle missing BOOT partition for SBC EFI-only disk layouts
0001 (overlay)	Toolchain	Bump Go to 1.24.13 (CVE fix)
0002 (overlay)	Upgrade	Detect EFI mount path for SBC layouts (no BOOT partition)

Roadmap

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

Status	Milestone	Description
Tested	4K page size	Aligned with upstream Talos kernel config. Reduces memory overhead and improves workload compatibility (Longhorn, jemalloc, F2FS, etc.).
Tested	Reliable in-place upgrades	Force GRUB bootloader with --no-nvram on arm64, handle SBC EFI-only disk layout. Verified end-to-end with talosctl upgrade.
Tested	Kernel <6.15 compatibility	Unconditional open_tree capability check — falls back to classic bind mounts on RPi downstream kernel 6.12.x.
Tested	Serial console	GPIO UART0 (ttyAMA0) via dtoverlay=uart0-pi5. Read-only output at 115200 baud, even parity. Verified on Compute Blade with FT232RNL adapter.
Tested	NVMe boot support	dd image to NVMe + set EEPROM BOOT_ORDER=0xf416 and PCIE_PROBE=1. Verified on 1TB Kingston NVMe on Compute Blade.

NVMe boot

The kernel has NVMe built-in (CONFIG_BLK_DEV_NVME=y), so booting from NVMe should work by flashing the disk image directly and configuring the RPi5/CM5 EEPROM.

1. Flash the image to NVMe

Connect the NVMe drive via a USB adapter and flash:

zstd -d metal-arm64.raw.zst | sudo dd of=/dev/<nvme-device> bs=4M status=progress
sync

2. Configure EEPROM boot order

Use rpiboot to update the CM5 EEPROM. Clone the usbboot repo and edit the boot config:

git clone --depth=1 https://github.com/raspberrypi/usbboot
cd usbboot && make
# Edit the EEPROM config for CM5
cp recovery/boot.conf recovery/boot.conf.bak

Add or update these values in recovery/boot.conf:

BOOT_ORDER=0xf416
PCIE_PROBE=1

Then flash via USB with the CM5 in USB boot mode (hold nRPIBOOT or disable eMMC boot on your carrier board):

sudo ./rpiboot -d recovery

BOOT_ORDER is read right-to-left: try NVMe (6) first, then SD (1), then USB (4), then restart (f). PCIE_PROBE=1 is required for non-HAT+ NVMe adapters (Compute Blade, most M.2 carrier boards).

3. Boot from NVMe

Power on. The RPi firmware should find the boot partition on NVMe, load U-Boot, and boot Talos.

Optional: enable PCIe Gen 3

PCIe Gen 3 doubles NVMe throughput (~400 MB/s → ~800 MB/s). Not officially certified by Raspberry Pi but stable on most NVMe drives.

New installs — PCIe Gen 3 is enabled by default in images built from this repo (config.txt.append includes dtparam=pciex1_gen=3).

Existing nodes — After a talosctl upgrade, the overlay rewrites config.txt with the baked-in settings (including PCIe Gen 3). If you need to enable it manually on an older image:

1. Power off the node and remove the NVMe drive
2. Connect via USB adapter and mount the first (EFI) partition
3. Add to config.txt under the [pi5] section:

   dtparam=pciex1_gen=3
   

4. Unmount, reinstall the drive, and power on

To verify after boot:

talosctl -n <ip> dmesg | grep -i pcie
# Look for "Gen 3" in the PCIe link speed output

Reference architecture

Recommended storage layout for production Talos clusters on CM5 Compute Blade hardware. Each CM5 has a 32GB eMMC and an M.2 NVMe slot.

Role	Boot disk	NVMe	EEPROM BOOT_ORDER	Rationale
Control plane	NVMe	Talos OS	0xf416 (NVMe first)	etcd lives on the STATE partition — NVMe gives ~800 MB/s sequential and ~50K random IOPS for fast consensus and snapshot I/O.
Postgres / storage	eMMC	Data (/var/mnt/data)	0xf214 (eMMC first)	Talos OS on eMMC keeps talosctl upgrade away from the data drive. The full 1TB NVMe is dedicated to database storage via machine.disks.
Compute workers	eMMC	None	0xf214 (eMMC first)	Stateless workloads — no local storage needed. eMMC is more than enough for Talos OS (~2.2GB used).

Storage configuration

Control planes — no extra config needed. Talos installs to the NVMe automatically when it's the boot disk.

Postgres / storage nodes — add machine.disks to mount the NVMe as a data volume:

machine:
    disks:
        - device: /dev/nvme0n1
          partitions:
              - mountpoint: /var/mnt/data

Talos automatically partitions, formats (XFS), and mounts the NVMe on first boot. The data persists across talosctl upgrade since upgrades only touch the boot disk (eMMC).

Compute workers — no storage config needed.

EEPROM setup

All CM5 modules require PCIE_PROBE=1 for NVMe detection on Compute Blade (non-HAT+ carrier). Set via rpiboot:

# recovery/boot.conf
BOOT_ORDER=0xf416   # NVMe-first (control planes)
# or
BOOT_ORDER=0xf214   # eMMC-first (storage/compute workers)
PCIE_PROBE=1         # always required

Overclock

All node types share the same overclock config (baked into the image via config.txt.append):

dtparam=pciex1_gen=3
dtoverlay=uart0-pi5
arm_freq=2600
over_voltage_delta=50000
arm_boost=1

Verified stable at 44.6°C max under full CPU + memory + disk stress across 10 nodes with Compute Blade heatsinks.

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.