diff --git a/kernel/sy_old/mars_light.c b/kernel/sy_old/mars_light.c
index d32c156a..ebd4f36d 100644
--- a/kernel/sy_old/mars_light.c
+++ b/kernel/sy_old/mars_light.c
@@ -3604,6 +3604,8 @@ static int check_deleted(void *buf, struct mars_dent *dent)
 enum {
 	// root element: this must have index 0
 	CL_ROOT,
+	// global ID
+	CL_UUID,
 	// global userspace
 	CL_GLOBAL_USERSPACE,
 	CL_GLOBAL_USERSPACE_ITEMS,
@@ -3655,6 +3657,15 @@ static const struct light_class light_classes[] = {
 	[CL_ROOT] = {
 	},
 
+	/* UUID, indentifying the whole cluster.
+	 */
+	[CL_UUID] = {
+		.cl_name = "uuid",
+		.cl_len = 4,
+		.cl_type = 'l',
+		.cl_father = CL_ROOT,
+	},
+
 	/* Subdirectory for global userspace items...
 	 */
 	[CL_GLOBAL_USERSPACE] = {
diff --git a/userspace/marsadm b/userspace/marsadm
index 8383cec8..15cee431 100755
--- a/userspace/marsadm
+++ b/userspace/marsadm
@@ -680,6 +680,19 @@ sub is_module_loaded {
 sub _create_cluster {
   my ($cmd) = @_;
   system("mkdir $mars") unless -d $mars;
+  my $old_uuid = get_link("$mars/uuid", 2);
+  if ($cmd eq "create-cluster") {
+    ldie "cluster was already created with uuid='$old_uuid'\n" if $old_uuid && !$force;
+    my $uuid = `echo -n \$(hostname) \$(date)`;
+    set_link($uuid, "$mars/uuid");
+    finish_links(); # opportunity for errors => don't continue
+  } elsif (!$old_uuid && !$force) {
+    if ($user_version == 0.1) {
+      my $uuid = `echo -n \$(hostname) \$(date)`;
+      set_link($uuid, "$mars/uuid");
+    }
+    ldie "cluster has no uuid\n" if $user_version > 0.1;
+  }
   system("mkdir $mars/ips") unless -d "$mars/ips";
   system("mkdir $mars/userspace") unless -d "$mars/userspace";
   system("mkdir $mars/defaults") unless -d "$mars/defaults";