Initial scaffolding and layout

Set up the modules of the flake. At this time, the flake is split into
modules and machines. Considering that additional top-level sections --
such as packages and shells -- will also be added, it might make sense
to keep all nix related things in one top-level directory, alongside the
flake.nix file.

This is all under the assumption that later amendments to the project
will introduce other tech, such as terraform.

4 files changed, 198 insertions, 0 deletions

diff --git a/modules/xnet/disk/boot.nix b/modules/xnet/disk/boot.nix
new file mode 100644
index 0000000..65be2f3
--- /dev/null
+++ b/modules/xnet/disk/boot.nix
@@ -0,0 +1,13 @@
+{ lib, ... }:
+let
+  inherit (lib) mkDefault;
+in
+{
+  boot = {
+    loader.systemd-boot.enable = true;
+    initrd.availableKernelModules = [ "xhci_pci" "ahci" "nvme" "usb_storage" "sd_mod" "sdhci_pci" ];
+    kernelModules = [ "kvm-intel" "kvm-amd" ];
+    swraid.mdadmConf = "MAILADDR = nobody@example.com";
+    tmp.cleanOnBoot = mkDefault true;
+  };
+}
diff --git a/modules/xnet/disk/default.nix b/modules/xnet/disk/default.nix
new file mode 100644
index 0000000..aca6ae2
--- /dev/null
+++ b/modules/xnet/disk/default.nix
@@ -0,0 +1,113 @@
+{ config, lib, modulesPath, ... }:
+let
+  cfg = config.xnet.disk;
+  commonOpts = {
+    acltype = "posixacl";
+    atime = "off";
+    compression = "on";
+    normalization = "formD";
+    relatime = "off";
+    xattr = "sa";
+    "com.sun:auto-snapshot" = "false";
+  };
+
+  inherit (lib) mkOption mkDefault mkIf types;
+in
+{
+  imports = [
+    ./boot.nix
+    (modulesPath + "/installer/scan/not-detected.nix")
+  ];
+
+  options.xnet.disk = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      description = "Apply xnet-standard ZFS disk layout.";
+    };
+
+    device = mkOption {
+      type = types.str;
+      description = "Underlying device that build the root ZFS pool.";
+    };
+
+    extraDatasets = mkOption { };
+  };
+
+  config = mkIf cfg.enable {
+    networking.hostId = builtins.substring 0 8
+      (builtins.hashString "md5" config.networking.hostName);
+
+    services.zfs = {
+      autoScrub.enable = true;
+      trim.enable = true;
+    };
+
+    zramSwap.enable = mkDefault true;
+
+    boot = {
+      kernelParams = [ "nohibernate" "elevator=none" ];
+      supportedFilesystems = [ "vfat" "zfs" ];
+      zfs.devNodes = "/dev/disk/by-partuuid";
+    };
+
+    disko.devices = (import ./layouts/single.nix cfg.device) // {
+      nodev."/" = {
+        fsType = "tmpfs";
+        mountOptions = [ "defaults" "size=2G" "mode=755" ];
+      };
+
+      zpool.zroot = {
+        type = "zpool";
+        options = {
+          ashift = "12";
+          autotrim = "on";
+        };
+
+        datasets = {
+          "local" = {
+            type = "zfs_fs";
+            options = commonOpts;
+          };
+
+          "local/reserved" = {
+            type = "zfs_fs";
+            options = {
+              refreservation = "10G";
+              mountpoint = "none";
+            };
+          };
+
+          "local/nix" = {
+            type = "zfs_fs";
+            mountpoint = "/nix";
+            options.mountpoint = "legacy";
+          };
+
+          "local/certs" = {
+            type = "zfs_fs";
+            mountpoint = "/certs";
+            options.mountpoint = "legacy";
+          };
+
+          "persist" = {
+            type = "zfs_fs";
+            mountpoint = "/persist";
+            options = { mountpoint = "legacy"; } // commonOpts;
+          };
+
+          "persist/data" = {
+            type = "zfs_fs";
+            mountpoint = "/persist/data";
+            options.mountpoint = "legacy";
+          };
+        } // cfg.extraDatasets;
+      };
+    };
+
+    users.groups.backup = {
+      members = [ config.services.syncoid.group ];
+      gid = 2001;
+    };
+  };
+}
diff --git a/modules/xnet/disk/layouts/mirror.nix b/modules/xnet/disk/layouts/mirror.nix
new file mode 100644
index 0000000..5a9835b
--- /dev/null
+++ b/modules/xnet/disk/layouts/mirror.nix
@@ -0,0 +1,43 @@
+devices: {
+  disk = builtins.listToAttrs (map
+    (device: {
+      name = device;
+      value = {
+        type = "disk";
+        device = "/dev/${device}";
+        content = {
+          type = "gpt";
+          partitions = {
+            ESP = {
+              size = "1G";
+              type = "EF00";
+              content = {
+                type = "mdraid";
+                name = "boot";
+              };
+            };
+            ZFS = {
+              size = "100%";
+              content = {
+                type = "zfs";
+                pool = "zroot";
+              };
+            };
+          };
+        };
+      };
+    })
+    devices);
+  mdadm = {
+    boot = {
+      type = "mdadm";
+      level = 1;
+      metadata = "1.0";
+      content = {
+        type = "filesystem";
+        format = "vfat";
+        mountpoint = "/boot";
+      };
+    };
+  };
+}
diff --git a/modules/xnet/disk/layouts/single.nix b/modules/xnet/disk/layouts/single.nix
new file mode 100644
index 0000000..b779a39
--- /dev/null
+++ b/modules/xnet/disk/layouts/single.nix
@@ -0,0 +1,29 @@
+device: {
+  disk = {
+    "${device}" = {
+      type = "disk";
+      device = "/dev/${device}";
+      content = {
+        type = "gpt";
+        partitions = {
+          ESP = {
+            size = "1G";
+            type = "EF00";
+            content = {
+              type = "filesystem";
+              format = "vfat";
+              mountpoint = "/boot";
+            };
+          };
+          ZFS = {
+            size = "100%";
+            content = {
+              type = "zfs";
+              pool = "zroot";
+            };
+          };
+        };
+      };
+    };
+  };
+}