My NixOS Configuration

Welcome to my NixOS configuration repository.
It contains my system configuration as well as custom Nix packages and development environments.

---

🧩 LuaMetaTeX (ConTeXt LMTX) Package

One of the highlights of this repository is the LuaMetaTeX package located in the
pkgs/context subdirectory.

This Nix package is based on the excellent work of Marco Feltmann
and has been adapted for a modern flake-based setup.

✨ Key Features

• Up-to-date sources – uses the current repository from contextgarden/context
• Essential fonts – downloads the texmf.zip archive from Pragma ADE
• Ready-to-use commands – builds luametatex, mtxrun, and context binaries that mirror upstream behavior

💡 Why LuaMetaTeX?

The ConTeXt typesetting system, primarily developed by Hans Hagen, offers a leaner and more structured codebase than LaTeX.
In practice, ConTeXt provides a cleaner macro language, integrated fonts and layouts, and very high-quality PDF output.

🛠 Building the package

From the repository root:

nix build .#context

The resulting binaries will appear in ./result/bin/.

To show more detailed build information:

nix build .#context --show-trace

A legacy non-flake build still works for compatibility:

nix-build -A luametatex pkgs/context

---

🏠 Personal NixOS Configuration

This repository also serves as a backup for my personal NixOS and Home-Manager configuration.
It may not be optimal in every respect, but it reflects my current setup and customization efforts.

🔁 Rebuilding the System

To apply changes to your system:

sudo nixos-rebuild switch

If fonts are missing or new ones were installed:

fc-cache -r

---

Feel free to explore, adapt, and reuse any part of this configuration for your own NixOS setup.

Arduino Uno USB passthrough with QEMU/KVM on kitty

kitty is the KVM-enabled host in this repository. For the MCT Bunny VMs, the Arduino Uno R3 is passed through as the real USB device with QEMU, for example:

-device usb-host,vendorid=0x2341,productid=0x0043

QEMU opens the raw host USB node under /dev/bus/usb/.... By default that node is typically root:root with mode 0664, so an unprivileged QEMU process can read it but cannot write to or claim the device. A one-off setfacl works, but the ACL disappears when the Arduino is unplugged because udev creates a new device node on the next plug-in.

The KVM module therefore creates the host-only group kvm-arduino, adds bernd to it, and installs a narrowly scoped udev rule for the official Uno R3 USB ID 2341:0043:

users.groups."kvm-arduino" = { };
users.users.bernd.extraGroups = [ "libvirtd" "kvm" "kvm-arduino" ];

services.udev.extraRules = ''
  SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", \
    ATTR{idVendor}=="2341", ATTR{idProduct}=="0043", \
    GROUP="kvm-arduino", MODE="0660"
'';

This is intentionally host-side only. The Bunny guest does not contain or need the kvm-arduino group. After passthrough, the guest sees the real Arduino as usual (normally /dev/ttyACM0), and guest access remains controlled by the normal dialout group. Converting the Bunny image to VMware therefore does not carry any kvm-arduino configuration into the student VM.

After changing this configuration on kitty:

sudo nixos-rebuild switch --flake .#kitty

Log out and back in once so the current login session picks up the new group, then unplug/replug the Uno. Verify on the host:

id -nG | tr ' ' '\n' | grep '^kvm-arduino$'

DEV=$(
  lsusb -d 2341:0043 |
  awk '{gsub(":", "", $4); printf "/dev/bus/usb/%s/%s\n", $2, $4}'
)

ls -l "$DEV"
getfacl "$DEV"

The raw USB node should be owned by group kvm-arduino and be writable by the group. This rule is intentionally limited to 2341:0043; Arduino clones or other boards with different USB vendor/product IDs need their own explicit rule.