Index: uspace/srv/fs/fat/fat_ops.c
===================================================================
--- uspace/srv/fs/fat/fat_ops.c	(revision 571addd173f588601486722216ec77880b28e1da)
+++ uspace/srv/fs/fat/fat_ops.c	(revision 69a60c4719c00c65754e37637d85664db3fa149f)
@@ -1564,6 +1564,25 @@
 void fat_sync(ipc_callid_t rid, ipc_call_t *request)
 {
-	/* Dummy implementation */
-	ipc_answer_0(rid, EOK);
+	dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
+	fs_index_t index = (fs_index_t) IPC_GET_ARG2(*request);
+	
+	fs_node_t *fn;
+	int rc = fat_node_get(&fn, dev_handle, index);
+	if (rc != EOK) {
+		ipc_answer_0(rid, rc);
+		return;
+	}
+	if (!fn) {
+		ipc_answer_0(rid, ENOENT);
+		return;
+	}
+	
+	fat_node_t *nodep = FAT_NODE(fn);
+	
+	nodep->dirty = true;
+	rc = fat_node_sync(nodep);
+	
+	fat_node_put(fn);
+	ipc_answer_0(rid, rc);
 }
 
Index: uspace/srv/fs/tmpfs/tmpfs_ops.c
===================================================================
--- uspace/srv/fs/tmpfs/tmpfs_ops.c	(revision 571addd173f588601486722216ec77880b28e1da)
+++ uspace/srv/fs/tmpfs/tmpfs_ops.c	(revision 69a60c4719c00c65754e37637d85664db3fa149f)
@@ -736,5 +736,8 @@
 void tmpfs_sync(ipc_callid_t rid, ipc_call_t *request)
 {
-	/* Dummy implementation */
+	/*
+	 * TMPFS keeps its data structures always consistent,
+	 * thus the sync operation is a no-op.
+	 */
 	ipc_answer_0(rid, EOK);
 }