nixpkgs/nixos/modules/system/service

Modular Services

This directory defines a modular service infrastructure for NixOS. See the Modular Services chapter in the manual [source].

Design decision log

• system.services.<name>. Alternatives considered

  • systemServices: similar to does not allow importing a composition of services into system. Not sure if that's a good idea in the first place, but I've kept the possibility open.
  • services.abstract: used in https://github.com/NixOS/nixpkgs/pull/267111, but too weird. Service modules should fit naturally into the configuration system. Also "abstract" is wrong, because it has submodules - in other words, evalModules results, concrete services - not abstract at all.
  • services.modular: only slightly better than services.abstract, but still weird

• No daemon.* options. https://github.com/NixOS/nixpkgs/pull/267111/files#r1723206521

• For now, do not add an enable option, because it's ambiguous. Does it disable at the Nix level (not generate anything) or at the systemd level (generate a service that is disabled)?

• Move all process options into a process option tree. Putting this at the root is messy, because we also have sub-services at that level. Those are rather distinct. Grouping them "by kind" should raise fewer questions.

• modules/system/service/systemd/system.nix has system twice. Not great, but

  • they have different meanings
    1. These are system-provided modules, provided by the configuration manager
    2. systemd/system configures SystemD system units.
  • This reserves modules/service for actual service modules, at least until those are lifted out of NixOS, potentially