{ pkgs, config, lib, ... }:
{
  # Users are managed through nix. If a user is added manually, it
  # will be removed on system activation.
  users.mutableUsers = false;

  boot = {
    loader = {
      # Use the systemd-boot EFI boot loader.
      systemd-boot.enable = true;
      # Prohibits gaining root access by passing init=/bin/sh as a
      # kernel parameter
      systemd-boot.editor = false;
      efi.canTouchEfiVariables = true;
    };

    tmp = {
      cleanOnBoot = true;
      useTmpfs = true;
    };
    kernelPackages = pkgs.linuxPackages_latest;
  };

  # Select internationalisation properties.
  i18n.defaultLocale = "en_US.UTF-8";

  time.timeZone = "America/Los_Angeles";

  # see https://www.man7.org/linux/man-pages/man5/loader.conf.5.html
  boot.loader.systemd-boot.consoleMode = "max";

  console = {
    earlySetup = true;
    font = "${pkgs.terminus_font}/share/consolefonts/ter-132n.psf.gz";
    packages = with pkgs; [ terminus_font ];
    keyMap = "us";
  };

  security.sudo.wheelNeedsPassword = false;
  security.polkit.enable = true;

  services.fstrim.enable = true;

  services.fwupd.enable = true;

  programs.ssh = {
    # $ ssh-keyscan example.com
    knownHosts = {
      github = {
        hostNames = [ "github.com" ];
        publicKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOMqqnkVzrm0SdG6UOoqKLsabgH5C9okWi0dh2l9GKJl";
      };
      rsync = {
        hostNames = [ "de2664.rsync.net" ];
        publicKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIObQN4P/deJ/k4P4kXh6a9K4Q89qdyywYetp9h3nwfPo";
      };
    };
  };

  nix = {
    package = pkgs.nixFlakes;
    settings = {
      trusted-users = [ "root" "@wheel" ];
      auto-optimise-store = true;
      substituters = [
        "https://cachix.cachix.org"
        "https://nix-community.cachix.org"
      ];
      trusted-public-keys = [
        "cachix.cachix.org-1:eWNHQldwUO7G2VkjpnjDbWwy4KQ/HNxht7H4SSoMckM="
        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
      ];
      experimental-features = [ "nix-command" "flakes" ];
      # Whether to warn about dirty Git/Mercurial trees - this is not
      # useful information to me.
      warn-dirty = false;
      # The timeout (in seconds) for establishing connections in the binary
      # cache substituter. It corresponds to curl’s –connect-timeout option.
      # The default is equivalent to 300 seconds, way too long.
      connect-timeout = 5;
      # The number of lines of the tail of the log to show if a build fails.
      # The default is 10 and it's usually too short.
      log-lines = 25;
      # If set to true, Nix will fall back to building from source if
      # a binary substitute fails. This is equivalent to the –fallback
      # flag. The default is false.
      fallback = true;
    };

    gc = {
      automatic = true;
      options = "--delete-older-than 14d";
    };
  };

  environment.shells = with pkgs; [ bashInteractive ];

  environment.systemPackages = with pkgs; [
    binutils
    cacert
    curl
    dmidecode
    ethtool
    flamegraph
    git
    htop
    hwdata
    iftop
    iptraf-ng
    linuxPackages.cpupower
    config.boot.kernelPackages.perf
    lm_sensors
    lsb-release
    lsof
    man-pages
    mg
    mtr
    numactl
    parted
    pciutils
    perf-tools
    powertop
    rsync
    sqlite
    strace
    tcpdump
    tmux
    traceroute
    unzip
    usbutils
    vim
    wget
    wireguard-tools

    # my custom tools
    tools.perf-flamegraph-pid
  ];

  programs.bcc.enable = true;
  programs.zsh.enable = true;

  # Show installed packages (https://www.reddit.com/r/NixOS/comments/fsummx/comment/fm45htj/?utm_source=share&utm_medium=web2x&context=3)
  environment.etc."installed-packages".text =
    let
      packages = builtins.map (p: "${p.name}") config.environment.systemPackages;
      sortedUnique = builtins.sort builtins.lessThan (lib.unique packages);
      formatted = builtins.concatStringsSep "\n" sortedUnique;
    in
    formatted;
}