Update files

hardware/filesystem.nix

@@ -9,8 +9,11 @@ in
     boot.initrd.postDeviceCommands = lib.mkAfter ''
         mkdir /btrfs_tmp
         mount ${rootDisk} /btrfs_tmp
+
+        # Ensure the old_roots directory exists
+        mkdir -p /btrfs_tmp/old_roots
+
         if [[ -e /btrfs_tmp/root ]]; then
-            mkdir -p /btrfs_tmp/old_roots
             timestamp=$(date +%Y-%m-%d_%H-%M-%S)
             mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp"
         fi
@@ -24,6 +27,8 @@ in
         }
 
         for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +7); do
+            # Don't delete the old_roots directory itself
+            if [[ "$i" == "/btrfs_tmp/old_roots/" ]]; then continue; fi
             delete_subvolume_recursively "$i"
         done