nixfiles/hosts/MacPro31/README.md

Mac Pro 3,1 (Early 2008) — install notes

Flake host: lyrathorpe-macpro31. Desktop (portable = false, imports ../../modules/desktop.nix). Files: configuration.nix, nvidia.nix, hardware-configuration.nix.

Hardware configuration

hardware-configuration.nix here is the real config generated by nixos-generate-config on the machine. Root is an LVM logical volume (/dev/mapper/MacPro-Root, ext4); the ESP (vfat) and swap are referenced by UUID. The initrd carries dm-snapshot for the LVM root. Regenerate and commit if the disk layout changes.

Bootloader

The Mac Pro 3,1 has 64-bit EFI, so it uses systemd-boot (no GRUB/CSM shim). canTouchEfiVariables = false because Apple's firmware does not reliably accept efibootmgr NVRAM writes.

Apple-EFI quirk: if the firmware boot picker does not show NixOS after install, either

• uncomment boot.loader.efi.efiInstallAsRemovable = true; in configuration.nix (installs the fallback \EFI\BOOT\BOOTX64.EFI), and/or
• "bless" the ESP from macOS.

Partition the disk GPT with an ESP (vfat).

Graphics — NVIDIA Quadro P400

The stock card (ATI Radeon HD 2600 XT or NVIDIA GeForce 8800 GT, depending on the unit) has been replaced with an NVIDIA Quadro P400 (Pascal, GP108). Everything driver-related lives in nvidia.nix:

• Driver branch 580 (nvidiaPackages.legacy_580), not the nixpkgs default (production, currently 595.x). 580 is the last branch that supports Maxwell/Pascal/Volta and is maintained as an LTS branch until Aug 2028; a newer branch does not drive this card at all.
• modesetting.enable = true — mandatory for Wayland (sets nvidia-drm.modeset=1); without it wlroots gets no GBM device and both Sway and the greeter fail to start.
• open = false — the open kernel modules require Turing or later.
• Sway runs with --unsupported-gpu (programs.sway.extraOptions); wlroots refuses the proprietary driver otherwise. cage/ReGreet needs no such flag.
• nouveau and nvidiafb are blacklisted automatically by the NVIDIA module.

The driver is unfree, so it is not in the binary cache: the kernel module is compiled on the machine, which on these 2008 Xeons is slow — budget for a long first rebuild and again after every kernel bump. The package names are allowlisted in unfreePackages in flake.nix.

Note the Mac Pro shows no EFI boot screen with a stock PC card (no Apple EFI ROM): the machine boots blind until KMS brings the display up. That is expected, not a fault.

Verify after a rebuild:

nvidia-smi

Docker with CUDA

nvidia.nix also enables Docker and gives containers GPU access via CDI (hardware.nvidia-container-toolkit.enable), which generates device specs from the host driver at boot (regenerated by a udev rule when the nvidia device appears) and turns on the daemon's CDI feature:

docker run --rm --device=nvidia.com/gpu=all nvidia/cuda:12.9.1-base-ubuntu24.04 nvidia-smi

• Use the --device=nvidia.com/gpu=all form. --gpus all is the legacy runtime-wrapper path (virtualisation.docker.enableNvidia), which is deprecated upstream and deliberately not enabled here.
• CUDA version matters. The P400 is compute capability 6.1 (sm_61); CUDA 13 dropped Maxwell/Pascal/Volta, so container images must ship a CUDA 12.x or older runtime. The 580 driver itself is happy with either.
• 2 GB of VRAM, 256 CUDA cores — fine for encode/decode and small models, not for training anything serious.
• Docker socket is local-only (no TCP listener, unlike the Pi). Users need the docker group; the registry already grants it.

"Driver Not Loaded" from the CDI generator

nvidia-container-toolkit-cdi-generator.service fails with failed to initialize NVML: Driver Not Loaded whenever the nvidia kernel module is not loaded in the running kernel. After a kernel bump that is unavoidable — the rebuilt module cannot load until reboot — so the unit is guarded with ConditionPathExists=/proc/driver/nvidia/version and skips instead of failing. Without that guard it also takes docker.service (requiredBy) with it and makes nixos-rebuild switch exit non-zero.

Reboot after a rebuild that touches the driver or the kernel. The toolkit's udev rule restarts the generator when the GPU device appears, so the CDI specs are written on the next boot. To check the state:

lsmod | grep nvidia            # nvidia, nvidia_modeset, nvidia_drm, nvidia_uvm
cat /proc/driver/nvidia/version
nvidia-smi
systemctl status nvidia-container-toolkit-cdi-generator.service
ls /var/run/cdi                # the generated spec

If the module is genuinely absent after a reboot, check dmesg | grep -i nvidia (build/version mismatch, or nouveau still bound — the module blacklists it, so that should not happen).

Claude Code — not installed here

The dual Harpertown Xeons are x86-64-v1 (SSE4.1, but no SSE4.2/POPCNT) and the Node runtime Claude Code ships on requires x86-64-v2. configuration.nix declares features.cpu.microarchLevel = 1, which switches the tool off through the fleet-wide gate in ../../modules/features.nix — see the root README. Forcing features.claudeCode.enable on here is an evaluation error, not a broken install.

Networking

Wired Ethernet via NetworkManager (from desktop.nix) — the Mac Pro has two gigabit ports.

Login

Graphical login via a Wayland greeter — greetd running ReGreet inside the cage kiosk compositor — configured centrally in ../../modules/sway.nix for every Sway host (gated on features.swayDesktop.enable). The greeter is forced to the Dvorak layout to match the console and Sway session. Set the user password (passwd lyrathorpe) after install, or the greeter cannot authenticate. Requires working KMS (NVIDIA modesetting — see Graphics).

Apply

sudo nixos-rebuild switch --flake .#lyrathorpe-macpro31