alo-cluster/nixos-setup/configuration.nix

{ config, pkgs, ... }:

let
  impermanence = builtins.fetchTarball "https://github.com/nix-community/impermanence/archive/master.tar.gz";
in
{
  imports =
    [
      "${impermanence}/nixos.nix"
      ./hardware-configuration.nix
    ];

  networking.hostName = "zippy";

  nix.settings.experimental-features = [ "nix-command" "flakes" ];
  nix.settings.trusted-users = [ "root" "@wheel" ];

  boot.initrd.kernelModules = [ "usb_storage" ];
  boot.initrd.luks.devices."luksroot" = {
      allowDiscards = true;
      bypassWorkqueues = true;
      keyFileSize = 4096;
      keyFile = "/dev/sdb";
  };

  swapDevices = pkgs.lib.mkForce [ {
    device = "/dev/disk/by-id/ata-KINGSTON_SKC600MS1024G_50026B7785AE0A92-part2";
    randomEncryption.enable = true;
  }];

  fileSystems."/".options = ["compress=zstd" "noatime" ];
  fileSystems."/nix".options = ["compress=zstd" "noatime" ];
  fileSystems."/persist".options = ["compress=zstd" "noatime" ];
  fileSystems."/persist".neededForBoot = true;
  fileSystems."/var/log".options = ["compress=zstd" "noatime" ];
  fileSystems."/var/log".neededForBoot = true;

  # reset / at each boot
  # Note `lib.mkBefore` is used instead of `lib.mkAfter` here.
  boot.initrd.postDeviceCommands = pkgs.lib.mkBefore ''
    mkdir -p /mnt

    # We first mount the btrfs root to /mnt
    # so we can manipulate btrfs subvolumes.
    mount -o subvol=/ /dev/mapper/luksroot /mnt

    # While we're tempted to just delete /root and create
    # a new snapshot from /root-blank, /root is already
    # populated at this point with a number of subvolumes,
    # which makes `btrfs subvolume delete` fail.
    # So, we remove them first.
    #
    # /root contains subvolumes:
    # - /root/var/lib/portables
    # - /root/var/lib/machines
    #
    # I suspect these are related to systemd-nspawn, but
    # since I don't use it I'm not 100% sure.
    # Anyhow, deleting these subvolumes hasn't resulted
    # in any issues so far, except for fairly
    # benign-looking errors from systemd-tmpfiles.
    btrfs subvolume list -o /mnt/root |
    cut -f9 -d' ' |
    while read subvolume; do
      echo "deleting /$subvolume subvolume..."
      btrfs subvolume delete "/mnt/$subvolume"
    done &&
    echo "deleting /root subvolume..." &&
    btrfs subvolume delete /mnt/root

    echo "restoring blank /root subvolume..."
    btrfs subvolume snapshot /mnt/root-blank /mnt/root

    # Once we're done rolling back to a blank snapshot,
    # we can unmount /mnt and continue on the boot process.
    umount /mnt
  '';

  # configure impermanence
  environment.persistence."/persist" = {
    directories = [
      "/etc/nixos"
    ];
    files = [
      "/etc/machine-id"
      "/etc/ssh/ssh_host_ed25519_key"
      "/etc/ssh/ssh_host_ed25519_key.pub"
      "/etc/ssh/ssh_host_rsa_key"
      "/etc/ssh/ssh_host_rsa_key.pub"
    ];
  };

  security.sudo = {
    extraConfig = ''
      # rollback results in sudo lectures after each reboot
      Defaults lecture = never
    '';
    wheelNeedsPassword = false;
  };

  # Use the systemd-boot EFI boot loader.
  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;

  networking.networkmanager.enable = true;

  time.timeZone = "Europe/Lisbon";

  users.mutableUsers = false;
  users.users.ppetru = {
    isNormalUser = true;
    extraGroups = [ "wheel" ];

    openssh.authorizedKeys.keys = [ "ssh-rsa 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 petru@paler.net" ];
  };

  environment.systemPackages = with pkgs; [
    vim
  ];

  services.openssh = {
    enable = true;
    settings = {
      PasswordAuthentication = false;
      KbdInteractiveAuthentication = false;
    };
    extraConfig = ''
      AllowTcpForwarding yes
      X11Forwarding no
      AllowAgentForwarding no
      AllowStreamLocalForwarding no
      AuthenticationMethods publickey
    '';
  };

  networking.firewall = {
    enable = false;
    allowedTCPPorts = [ 22 ];
    allowedUDPPorts = [ ];
  };

  # Copy the NixOS configuration file and link it from the resulting system
  # (/run/current-system/configuration.nix). This is useful in case you
  # accidentally delete configuration.nix.
  system.copySystemConfiguration = true;

  # This value determines the NixOS release from which the default
  # settings for stateful data, like file locations and database versions
  # on your system were taken. It's perfectly fine and recommended to leave
  # this value at the release version of the first install of this system.
  # Before changing this value read the documentation for this option
  # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
  system.stateVersion = "24.05"; # Did you read the comment?
}