{ config, pkgs, ... }:

{
  # Enable automatic garbage collection (prevents /boot or / filling up)
  nix.gc.automatic     = true;
  nix.gc.dates         = "03:00";           # run GC at 03:00 daily
  nix.gc.options       = "--delete-older-than 30d"; # drop generations older than 30 days
  nix.optimise.automatic = true;            # hard-link identical store files

  # This host has no configuration.nix: point <nixos-config> at master.nix,
  # otherwise nixos-upgrade.service (and plain nixos-rebuild) cannot find the config.
  nix.nixPath = [
    "nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos"
    "nixos-config=/etc/nixos/master.nix"
    "/nix/var/nix/profiles/per-user/root/channels"
  ];

  # Enable automatic system upgrades
  system.autoUpgrade = {
    enable             = true;               # turn on unattended upgrades
    dates              = "02:00";            # schedule upgrades at 02:00 each day
    randomizedDelaySec = "45m";              # spread load by up to 45 minutes
    allowReboot        = false;              # don't reboot if needed for new generation
  };

}