nixfiles/system/machine/T400/README.md

# ThinkPad T400 — install notes

Flake host: `lyrathorpe-t400`. Files: `configuration.nix`, the `boot-*.nix`
variants, and `hardware-configuration.nix`.

## Hardware configuration

`hardware-configuration.nix` here is a hand-written **placeholder**. On the real
machine, run `nixos-generate-config`, replace the file, and commit it. It assumes
by-label partitions — root `nixos` (ext4) and `swap` — so either label them at
install time or swap in the generated UUIDs.

## Bootloader — import the module matching the flashed firmware

`configuration.nix` imports exactly one boot module. Default is `boot-bios.nix`;
switch by commenting it out and uncommenting the relevant alternative.

| Firmware                                             | Module                   | Notes                                                                                                                                                                                                                                                                                 |
| ---------------------------------------------------- | ------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Stock Lenovo BIOS, or coreboot + **SeaBIOS** payload | `boot-bios.nix`          | GRUB on the MBR. Set `device` to the real install disk (`/dev/sda` by default). MBR/legacy layout.                                                                                                                                                                                    |
| coreboot + **GRUB** payload                          | `boot-coreboot-grub.nix` | GRUB is config-only (`device = "nodev"`); NixOS does **not** write to a disk. Your coreboot `grub.cfg` (in the flash chip) must `search` for and `configfile` the on-disk `/boot/grub/grub.cfg`, or chainload the disk's GRUB.                                                        |
| coreboot + **Tianocore/edk2 (UEFI)** payload         | `boot-coreboot-uefi.nix` | systemd-boot. `canTouchEfiVariables = true` (coreboot honours NVRAM writes). The module **declares its own ESP** (`/boot` vfat, label `ESP`) — when you regenerate `hardware-configuration.nix`, do **not** let it also define `/boot`. Create + label an `ESP` vfat partition (GPT). |

## Graphics

This unit has the optional **discrete ATI Mobility Radeon HD 3470 (RV620)**. The
open `radeon` KMS driver is loaded in the initrd for early modesetting; firmware
comes from `enableRedistributableFirmware`.

The T400 has switchable graphics (discrete ATI + Intel GMA 4500MHD). Select
**Discrete** in the firmware's graphics setting so only the ATI is live. If you
run **Integrated** instead, the Intel `i915` driver takes over with no config
change and `radeon` stays idle.

## Login

Graphical login via a Wayland greeter — `greetd` running ReGreet inside the
`cage` kiosk compositor — configured centrally in `lyrathorpe/swaywm.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 radeon/i915 KMS (see Graphics).

## Apply

```sh
sudo nixos-rebuild switch --flake .#lyrathorpe-t400
```