Hosts

This directory contains all host-specific configurations for my NixOS and macOS systems.

Current Host Inventory

Physical Machines

`idols` - Main Workstations

Named after characters from "Oshi no Ko":

Host	Platform	Hardware	Purpose	Status
`ai`	NixOS	Ultra 7 270K Plus + RTX 4090, 128G DDR5	Gaming & Daily Use	✅ Active
`kana`	NixOS (libvirt)	Virtual	Run AI Agents	✅ Active
`ruby`	NixOS (libvirt)	Virtual	Run AI Agents	✅ Active
`akane`	NixOS (aarch64)	Virtual (UTM)	aarch64 test VM	✅ Active

On 2026-04-27 ai was rebuilt on a new platform. The MSI board and i5-13600KF it was added with in 2023-05 (the host was originally named msi-rtx4090) gave way to the Colorful CVN Z890 ARK FROZEN + Intel Core Ultra 7 270K Plus. The traces in the history are PR #257 (the NIC moved from enp5s0 to enp130s0) and PR #258 (Niri output names renamed, hardware-intel.nix added with the Arrow Lake NPU, kernel moved to linuxPackages_latest). The 2×48G DDR5 kit was already in place at that point; the repo has no record of when it went in.

On 2026-10-06 ai grew from 2×48G (96G) to 2×48G + 2×16G (128G) across all four DIMM slots, at DDR5-4800 with XMP off — the only stable setting with four DIMMs on this board. The 16G pair must be installed first; with the 48G pair in first the board does not POST. The bring-up order, the BIOS settings, the stress-test recipe, and how to recover a board that will not POST are in idols-ai/MIXED-MEMORY.md.

Retired

Host	Platform	Hardware	Purpose	Status
`aquamarine`	NixOS (libvirt)	Virtual	Monitoring & Services	⚪ Retired

aquamarine is retired; its services now run directly on youko (hosts/12kingdoms-youko/homelab-services/).

`darwin` - macOS Systems

Named after characters from "Frieren: Beyond Journey's End":

Host	Platform	Hardware	Purpose	Status
`fern`	macOS	MacBook Pro M2 13" 16GB	Personal Use	✅ Active
`frieren`	macOS	MacBook Pro M4Pro 14" 48GB	Work Use	✅ Active

`12kingdoms` - Homelab Servers & Apple Silicon Linux

Named after "Twelve Kingdoms":

Host	Platform	Hardware	Purpose	Status
`shoukei`	NixOS	MacBook Pro M2	NixOS on Apple Silicon	✅ Active
`shoryu`	NixOS	MoreFine S500+ (AMD Ryzen 7 5825U)	VM Host	✅ Active
`shushou`	NixOS	MinisForum UM560 (AMD Ryzen 5 5625U)	VM Host	✅ Active
`youko`	NixOS	Beelink GTR5 (AMD Ryzen 9 5900HX)	Homelab Core	✅ Active

On 2026-09-29 the NVMe SSDs of youko and shushou were physically swapped, and the 2×4TB USB HDDs moved with the youko role to the other chassis. The reason was Jellyfin: HDR transcoding on the 5625U's Barceló iGPU could not keep up (~0.4–0.8×), while the 5900HX's Cezanne iGPU can (~1.68× for 1080p HDR). So the homelab-core role (all services + the k3s VMs + the HDDs + the UPS) now runs on the Beelink GTR5 and the k3s VM-host role on the UM560; the other services moving along is a side effect of swapping the role's disk, not a separate migration. Hostnames, IPs, and state followed the disks.

Virtual Machines & Clusters

`k8s` - Kubernetes Infrastructure

VM Cluster: 3 physical mini PCs (shoryu, shushou, youko) running all VMs
K3s Testing: k3s-test-1 control plane and workers, running as microVMs; placement and rollout are documented in k8s/README.md

External Systems

SBCs: aarch64/riscv64 single-board computers managed in ryan4yin/nixos-config-sbc

All my riscv64 hosts:

Naming Conventions

idols: Characters from "Oshi no Ko" anime/manga
12kingdoms: Characters from "Twelve Kingdoms" anime/novel series
darwin: Characters from "Frieren: Beyond Journey's End" anime/manga
k8s: Kubernetes-related systems follow standard naming patterns

How to Add a New Host

Copy the closest existing host and adapt it. The step-by-step procedure, including the outputs and networking wiring, secrets, and the eval tests a new host must pass, is in .agents/skills/nix-config-new-host/SKILL.md.

Deploying VM Hosts

The three VM hosts (shoryu, shushou, youko) put their VMs on the Linux bridge br0, with the physical NIC as a bridge port. NixOS guests run as microVMs (microvm.nix); the k3s-test-1 cluster is microVMs on top, using Cilium as its pod network (flannel disabled). Full-machine guests run with qemu-kvm under libvirt instead: shoryu is the only host that enables libvirtd today (the agent desktops kana/ruby). Non-NixOS guests (Ubuntu, Windows, Qubes OS) would take the same qemu-kvm path; there are none right now.

switch is fine for changes that don't touch the network stack (e.g. journald or other service settings). Deploy serially (-p 1) and re-check VM reachability afterwards.
Use boot + a serial reboot for anything that can drop the network mid-flight — systemd.network / br0 changes, nixpkgs updates, or any broad rebuild.
If a host loses VM networking, check br0 and the VM taps, or reboot the host.

Common Build Commands

Use the Just recipes for host configuration checks and builds:

just eval-host <host>
just build-host <host>

eval-host only evaluates the configuration. build-host builds the system closure without activating it. Host activation remains an explicit Colmena operation such as just shoryu, just shushou, or just youko.

Distributed Building

I usually run the build command on Ai and nix will distribute the build to other NixOS machines, which is convenient and fast.

When building some packages for riscv64 or aarch64, I often have no cache available because of various changes under the hood, so I need to build much more packages than usual, which is one of the reasons why the cluster was originally built, and another reason is distributed building is cool!