Index: grub2-2.12/util/deviceiter.c
===================================================================
--- grub2-2.12.orig/util/deviceiter.c
+++ grub2-2.12/util/deviceiter.c
@@ -398,6 +398,12 @@ get_rump_disk_name (char *name, int unit
 {
   sprintf (name, "/dev/wd%d", unit);
 }
+
+static void
+get_rump_usb_disk_name (char *name, int unit)
+{
+  sprintf (name, "/dev/ud%d", unit);
+}
 #endif
 
 static struct seen_device
@@ -1059,6 +1065,19 @@ dmraid_end:
       if (check_device_readable_unique (name))
 	{
 	  if (hook (name, 0, hook_data))
+	    goto out;
+	}
+    }
+
+  /* Rump-supported USB disks.  */
+  for (i = 0; i < 96; i++)
+    {
+      char name[16];
+
+      get_rump_usb_disk_name (name, i);
+      if (check_device_readable_unique (name))
+	{
+	  if (hook (name, 0, hook_data))
 	    goto out;
 	}
     }
