add a module for mounting CIFS volumes

The new module is for NAS clients, where we specify the server and the
paths to mount locally.

We add a new secret to have the username of the `nas' user.

We mount the backups volume from the NAS under `/data/backups` on the
VM.

1 files changed, 84 insertions, 0 deletions

diff --git a/modules/nas-client.nix b/modules/nas-client.nix
new file mode 100644
index 0000000..fe0952e
--- /dev/null
+++ b/modules/nas-client.nix
@@ -0,0 +1,84 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  cfg = config.my.modules.nas-client;
+in
+{
+  options.my.modules.nas-client = with lib; {
+    enable = mkEnableOption "NAS client";
+
+    volumes = mkOption {
+      type = types.attrsOf (
+        types.submodule {
+          options = {
+            server = mkOption {
+              type = types.str;
+              example = "nas";
+              description = "Hostname of the server to connect to.";
+            };
+            remotePath = mkOption {
+              type = types.str;
+              example = "data";
+              description = "Remote path on the NAS to mount.";
+            };
+            mountPoint = mkOption {
+              type = types.str;
+              description = "Local directory where the volume will be mounted.";
+            };
+            uid = mkOption {
+              type = types.int;
+              default = 1000;
+              description = "User ID for mounted files.";
+            };
+            gid = mkOption {
+              type = types.int;
+              default = 1000;
+              description = "Group ID for mounted files.";
+            };
+            options = mkOption {
+              type = types.str;
+              default = "rw";
+              description = "Additional mount options.";
+            };
+          };
+        }
+      );
+      default = { };
+      description = "NAS volumes to mount.";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    boot.kernelModules = [
+      "cifs"
+      "cmac"
+      "sha256"
+    ];
+
+    # this is required to get the credentials options to work
+    environment.systemPackages = [ pkgs.cifs-utils ];
+
+    systemd.mounts = lib.mapAttrsToList (name: volume: {
+      description = "Mount for NAS volume ${name}";
+      what = "//${volume.server}/${volume.remotePath}";
+      where = volume.mountPoint;
+      unitConfig = {
+        # This ensures it uses mount.cifs
+        Type = "cifs";
+      };
+      type = "cifs"; # Explicitly specify CIFS type otherwise we ran into issues when using the credentials file option
+      options = "credentials=${config.age.secrets.nas_client_credentials.path},uid=${toString volume.uid},gid=${toString volume.gid},${volume.options}";
+    }) cfg.volumes;
+
+    systemd.automounts = lib.mapAttrsToList (name: volume: {
+      description = "Automount for NAS volume ${name}";
+      where = volume.mountPoint;
+      wantedBy = [ "multi-user.target" ];
+    }) cfg.volumes;
+  };
+}