up and running again

modules/system/btrfs-conf.nix

@@ -0,0 +1,31 @@
+{ config, lib, pkgs, ... }:
+
+{
+  services = {
+    btrfs = {
+      autoScrub = {
+        enable = true;
+      };
+    };
+    btrbk = {
+      instances."home" = {
+        onCalendar = "hourly";
+        settings = {
+          timestamp_format = "long";
+          snapshot_preserve_min = "18h";
+          snapshot_preserve = "48h";
+          volume = {
+            "/" = {
+              snapshot_dir = "/.snapshots";
+              subvolume = "/home";
+            };
+          };
+        };
+      };
+    };
+  };
+
+  systemd.tmpfiles.rules = [
+    "d /.snapshots 0755 root root"
+  ];
+}