TODO.md

• add support for tmpfiles' modifiers?
• maybe add some recommended config that users can opt-in to use in addition to preservation?
• with the recent upstream changes the handling of /etc/machine-id changed. That requires another change upstream, i.e. the file needs to be created with content uninitialized\n and on a setup with preservation something like the following needs to be done to properly preserve the machine-id across reboots.

  {
    preservation.preserveAt."/state".files = [
      { file = "/etc/machine-id"; inInitrd = true; how = "symlink"; }
    ];
  
    systemd.services.systemd-machine-id-commit = {
      unitConfig.ConditionPathIsMountPoint = [
        "" "/state/etc/machine-id"
      ];
      serviceConfig.ExecStart = [
        "" "systemd-machine-id-setup --commit --root /state"
      ];
    };
  }

  see NixOS/nixpkgs#351151 (comment)