feat: Add host sydpc

My, this is a lot TwT.  Much work was batched as part of the transition from
guix-rebound to nixos-testbed/sydpc.

- Discord/Vesktop module & config.
- Syncthing setup.
- Assorted Emacs changes.
- Waybar config.
- Niri config.
- Steam config.
- Some MPD.
- Stylix config.
- Files/Impermanence things.
- Enable Ghostty.
- God knows what else.

hosts/sydpc/configuration.nix

@@ -0,0 +1,160 @@
+{ config, pkgs, lib, disko, sydnix-cli, ... }:
+
+{
+  imports = [
+    ./hardware.nix
+    ./disks.nix
+  ];
+
+  sydnix = {
+    filesystemType = "btrfs";
+
+    steam.enable = true;
+    niri.enable = true;
+    stylix.enable = true;
+
+    users.users = [
+      "crumb"
+    ];
+
+    impermanence = {
+      enable = true;
+      directories = [
+        # "Warning: Neither /var/lib/nixos nor any of its parents are persisted.
+        # This means all users/groups without specified uids/gids will have them
+        # reassigned on reboot."
+        "/var/lib/nixos"
+        # We don't want to have different ssh keys on reboot, because ssh keys
+        # are expected to consistently identify machines... I think.  I mostly
+        # just think it's annoying to edit ~/.ssh/known_hosts all the time.
+        "/etc/ssh"
+      ];
+      rollback = {
+        enable = true;
+        device = "/dev/disk/by-partlabel/disk-bootroot-root";
+        subvolume = "rootfs";
+      };
+    };
+  };
+
+  # Disable systemd-sleep.  Let KDE or whatever dim the screen without
+  # suspending the computer.
+  systemd.sleep.extraConfig = ''
+    AllowSuspend=no
+    AllowHibernation=no
+    AllowHybridSleep=no
+    AllowSuspendThenHibernate=no
+  '';
+
+  boot.loader = {
+    grub.enable = false;
+    systemd-boot.enable = true;
+    efi.canTouchEfiVariables = false;
+  };
+
+  time.timeZone = "America/Denver";
+
+  i18n.defaultLocale = "en_US.UTF-8";
+
+  console = {
+    font = "Lat2-Terminus16";
+    useXkbConfig = true; # Use xkb.options in tty.
+  };
+
+  hardware.nvidia.open = false;
+
+  services.xserver = {
+    enable = true;
+    videoDrivers = [ "nvidia" ];
+    xkb = {
+      layout = "us";
+      options = "ctrl:swapcaps";
+    };
+  };
+
+  services.displayManager.sddm.enable = true; # WAIT4NIRI
+  services.desktopManager.plasma6.enable = true; # WAIT4NIRI
+
+  services.libinput = {
+    enable = true;
+    # Disable mouse acceleration.
+    mouse.accelProfile = "flat";
+    # Sensitivity.
+    mouse.accelSpeed = "-0.5";
+  };
+
+  services.pipewire = {
+    enable = true;
+    alsa.enable = true;
+    alsa.support32Bit = true;
+    pulse.enable = true;
+    wireplumber.enable = true;
+  };
+
+  services.pulseaudio.package = pkgs.pulseaudioFull;
+
+  # Usually we try to delegate declarations of globally-available packages to
+  # separate modules.  These are some exceptional essentials.
+  environment.systemPackages = [
+    pkgs.neovim
+    pkgs.git
+    sydnix-cli.packages.x86_64-linux.default
+    (import ../../scripts/port-tools { inherit pkgs; })
+
+    # Waypipe provides the equivalent of X11 forwarding for Wayland.  When
+    # connecting to a remote, it is required that `waypipe` is on the remote's
+    # PATH, thus we include it globally here.
+    pkgs.waypipe
+    pkgs.cachix
+  ];
+
+  programs.xwayland.enable = true;
+
+  services.openssh = {
+    enable = true;
+    settings.PermitRootLogin = "yes";
+    settings.X11Forwarding = true;
+  };
+
+  # TODO: Move to defaults.
+  users.mutableUsers = false;
+
+  nix = {
+    settings = {
+      trusted-users = [
+        "@wheel"
+      ];
+      substituters = [
+        "https://cache.deertopia.net"
+        "https://nix-community.cachix.org"
+        "https://cache.nixos.org"
+      ];
+      trusted-public-keys = [
+        (builtins.readFile ../../public-keys/deertopia-cache.pub.pem)
+        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      ];
+    };
+  };
+
+  # This option defines the first version of NixOS you have installed on this
+  # particular machine, and is used to maintain compatibility with application
+  # data (e.g. databases) created on older NixOS versions.
+  #
+  # Most users should NEVER change this value after the initial install, for any
+  # reason, even if you've upgraded your system to a new NixOS release.
+  #
+  # This value does NOT affect the Nixpkgs version your packages and OS are
+  # pulled from, so changing it will NOT upgrade your system - see
+  # https://nixos.org/manual/nixos/stable/#sec-upgrading for how to actually do
+  # that.
+  #
+  # This value being lower than the current NixOS release does NOT mean your
+  # system is out of date, out of support, or vulnerable.
+  #
+  # Do NOT change this value unless you have manually inspected all the changes
+  # it would make to your configuration, and migrated your data accordingly.
+  #
+  # For more information, see `man configuration.nix` or
+  # https://nixos.org/manual/nixos/stable/options#opt-system.stateVersion .
+  system.stateVersion = "24.05"; # Did you read the comment?
+}

hosts/sydpc/disks.nix

@@ -0,0 +1,73 @@
+# sudo nix --experimental-features "nix-command flakes" run github:nix-community/disko/latest -- --mode disko /persist/dots/hosts/nixos-testbed/disko-config.nix
+# time sudo nixos-install --flake /persist/dots#nixos-testbed
+{ lib, ... }:
+{
+  # imports = [ disko.nixosModules.disko ];
+  boot.initrd.supportedFilesystems.btrfs = true;
+  boot.supportedFilesystems.btrfs = true;
+
+  # From Impermanence's README: "Important note: Make sure your persistent
+  # volumes are marked with neededForBoot, otherwise you will run into
+  # problems."
+  fileSystems."/persist".neededForBoot = true;
+
+  disko.devices = {
+    disk = {
+      bootroot = {
+        type = "disk";
+        device = "/dev/disk/by-id/ata-Samsung_SSD_870_EVO_1TB_S75BNL0WA33853H";
+        content = {
+          type = "gpt";
+          partitions = {
+            ESP = {
+              size = "512M";
+              type = "EF00";
+              content = {
+                type = "filesystem";
+                format = "vfat";
+                mountpoint = "/boot";
+                mountOptions = [ "umask=0077" ];
+              };
+            };
+            root = {
+              size = "100%";
+              content = {
+                type = "btrfs";
+
+                mountpoint = "/partition-root";
+                swap.swapfile.size = "4G";
+
+                # Override existing partitions.
+                extraArgs = [ "-f" ];
+
+                # Subvolumes must set a mountpoint in order to be mounted,
+                # *unless their parent is mounted*.
+                subvolumes = {
+                  # Subvolume names do not necessarily correspond to
+                  # mountpoints, despite the structural resemblance to a file
+                  # path.
+                  "/rootfs" = {
+                    mountpoint = "/";
+                  };
+                  "/nix" = {
+                    mountpoint = "/nix";
+                  };
+                  "/persist" = {
+                    mountpoint = "/persist";
+                  };
+                  "/persist/home" = {
+                    mountpoint = "/persist/home";
+                  };
+                  "/swap" = {
+                    mountpoint = "/.swapvol";
+                    swap.swapfile.size = "4G";
+                  };
+                };
+              };
+            };
+          };
+        };
+      };
+    };
+  };
+}

hosts/sydpc/hardware.nix

@@ -0,0 +1,25 @@
+# Do not modify this file!  It was generated by ‘nixos-generate-config’
+# and may be overwritten by future invocations.  Please make changes
+# to /etc/nixos/configuration.nix instead.
+{ config, lib, pkgs, modulesPath, ... }:
+
+{
+  imports =
+    [ (modulesPath + "/installer/scan/not-detected.nix")
+    ];
+
+  boot.initrd.availableKernelModules = [ "xhci_pci" "ahci" "usbhid" "usb_storage" "sd_mod" ];
+  boot.initrd.kernelModules = [ ];
+  boot.kernelModules = [ "kvm-intel" ];
+  boot.extraModulePackages = [ ];
+
+  # Enables DHCP on each ethernet and wireless interface. In case of scripted networking
+  # (the default) this is the recommended approach. When using systemd-networkd it's
+  # still possible to use this option, but it's recommended to use it in conjunction
+  # with explicit per-interface declarations with `networking.interfaces.<interface>.useDHCP`.
+  networking.useDHCP = lib.mkDefault true;
+  # networking.interfaces.enp0s31f6.useDHCP = lib.mkDefault true;
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+  hardware.cpu.intel.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;
+}

hosts/sydpc/system.nix

@@ -0,0 +1 @@
+"x86_64-linux"