Administration modules

Note

A administration module deals with system-specific functionalities for administrators.

👑 darkone.admin.nix

NixOS configuration for the local LAN administrator computer.

Build farm (remote builders)

An admin host builds every node closure locally and pushes it (buildOnTarget empty, see assets/just/project.just), so it is the machine that actually compiles. Any fleet host flagged build-farm in config.yaml becomes one of its nix.buildMachines, reached over SSH as the nix deploy user.

Delegation is deliberately narrow. mandatoryFeatures (default big-parallel) means the farm is offered only the derivations that declare requiredSystemFeatures = [ "big-parallel" ] — kernel, chromium, firefox, llvm, rustc… ie. the long builds a beefy host is wanted for. Anything else stays local, which matters when the farm sits behind a slow uplink: only the requested output travels back.

Never drop big-parallel from this host’s own nix.settings.system-features to force delegation: keeping it means an unreachable farm makes the build hook decline and the derivation is simply built locally instead of failing.

Deploy key required

sshKey points at the shared deploy key just configure-admin-host generates under the nix user’s home. Admin hosts hold it by construction; a host that enables this module without the key logs SSH failures on every delegated build.

Why not a binary cache

A harmonia on the farm would share its build results, but harmonia serves the whole /nix/store and cannot express “only what I compiled”: it captures traffic the public cache should answer. Offloading is a build-scheduling concern, not a substitution one — hence buildMachines here and a last-resort substituter priority in service/nix-cache.nix.

• enable bool Enable NIX configuration builder tools
• enableNh bool Enable nix helper (nh) management tool
• remoteBuilders.enable bool Offload builds to the fleet hosts flagged build-farm in config.yaml. Inert while no host carries the flag.
• remoteBuilders.maxJobs int Parallel build slots to use on each farm.
• remoteBuilders.speedFactor int Relative speed rating of a farm, compared to this host.
• remoteBuilders.mandatoryFeatures listOf str Features a derivation MUST require for a farm to be offered it. This is what keeps small derivations off a remote (possibly slow) link. An empty list sends every eligible derivation to the farm.
• remoteBuilders.supportedFeatures listOf str System features a farm can provide.
• remoteBuilders.systems listOf str Platforms a farm builds for. Explicit rather than derived: hosts.nix only carries an architecture when it differs from the default.

darkone.admin.nix = {
  enable = false;
  enableNh = false;
  remoteBuilders.enable = true;
  remoteBuilders.maxJobs = 8;
  remoteBuilders.speedFactor = 2;
  remoteBuilders.mandatoryFeatures = [ ];
  remoteBuilders.supportedFeatures = [ ];
  remoteBuilders.systems = [ ];
};

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