{ pkgs, config, ... }: {
  nix = {
    package = pkgs.nixUnstable; # or versioned attributes like nix_2_4
    extraOptions = ''
      experimental-features = nix-command flakes
    '';
  };

  system.activationScripts.report-nixos-changes = ''
    if [ -e /run/current-system ] && [ -e $systemConfig ]; then
      echo System package diff:
      ${config.nix.package}/bin/nix store diff-closures /run/current-system $systemConfig || true
    fi
  '';

  # Select internationalisation properties.
  i18n.defaultLocale = "en_US.UTF-8";
  console = {
    #font = "Lat2-Terminus16";
    font = "${pkgs.terminus_font}/share/consolefonts/ter-u28n.psf.gz";
    keyMap = pkgs.lib.mkForce "uk";
  };

  # Enable the OpenSSH daemon.
  services.openssh.enable = true;

  # set root ssh keys
  users.users.root.openssh.authorizedKeys = {
    keys = [
      # RSA keys go into keyFiles because they're shamefully long
      # "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIPS8xkNH7JvKblekx5oel4HVKCz3uBbQYEaR9Z9nzTAr manuel@ifsr.de"
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAINogGKyXieCXQvVTa1z3ArS1TlqcVl2sSqvMpOjQo/Um jakob@krbs.me"
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICjNYNRBsY/Dc+/XOaGDui9tRa4VGPsHwYo3irGnMRbR felix@tycho"
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIDdOcXORg+akeN2t3yZlKWdoTURKxtV29eQ7UrIMkCHv felix@entropy"
      # "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIH73n+ZfJqNzIh9rPh6JYQaI4OAw9WKkPeqj2XRFmRfQ pascal@ifsr.de"
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIAmb1kv+7HU1QKE53+gNxUhrggbwomC40Xjxd9hACkoo bennofs@d-cube"
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIA0X6L7NwTHiOmFzo8mJBCy6H+DKUePAAXU4amm32DAQ fugi@arch"
      "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHD1ZkrAmC9g5eJPDgv4zuEM+UIIEWromDzM1ltHt4TM fugi@macbook"
      # "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICBtP2ltExnQL5llOvfSKp6OCZKbPWsa2s6P0i00XyrH helene_emilia.hausmann@mailbox.tu-dresden.de"
      # "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIEXMHwy4AZ9B4pMRBa/P/rb7N3SCas9e7Lp89plTHdFS halcyon@eisvogel.moe"
      # "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIAJ7qUGZUjiDhQ6Se+aXr9DbgRTG2tx69owqVMkd2bna simon@mayushii"
      "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBLlITzcTVnSi8EpEW3leSuqYCDhbnJyoGCjFOtIJ0Dl5uRNm0UNXS7AbQtLLylEeI1+/qinQDEWAJ6cBDAaPfNw= rouven@thinkpad"

    ];
    keyFiles = [
      ../keys/ssh/marcus-sapphire
      ../keys/ssh/schrader
      ../keys/ssh/jannusch
      ../keys/ssh/jannusch-arch
      ../keys/ssh/tassilo
      ../keys/ssh/jonasga
      ../keys/ssh/rouven
      ../keys/ssh/joachim
    ];
  };

  time.timeZone = "Europe/Berlin";

  # basic shell & editor
  programs.vim.defaultEditor = true;

  # List packages installed in system profile. To search, run:
  # $ nix search wget
  environment.systemPackages = with pkgs; [
    atop
    bat
    git
    htop
    fd
    ripgrep
    tldr
    tmux
    usbutils
    wget
    neovim
    helix
    nmap
    tcpdump
    bat
    dig
    ethtool
    iftop
    ipcalc
    iperf3
    ipv6calc
    lsof
    ltrace
    strace
    mtr
    traceroute
    smartmontools
    sysstat
    tree
    whois
    exa
    zsh
  ];
}