--- a/util/grub-setup.c
+++ b/util/grub-setup.c
@@ -141,12 +141,11 @@ write_rootdev (char *core_img, grub_devi
 static void
 setup (const char *dir,
        const char *boot_file, const char *core_file,
-       const char *dest, int force,
+       const char *root, const char *dest, int force,
        int fs_probe, int allow_floppy)
 {
   char *boot_path, *core_path, *core_path_dev, *core_path_dev_full;
   char *boot_img, *core_img;
-  char *root = 0;
   size_t boot_size, core_size;
   grub_uint16_t core_sectors;
   grub_device_t root_dev = 0, dest_dev, core_dev;
@@ -253,7 +252,10 @@ setup (const char *dir,
 
   core_dev = dest_dev;
 
-  {
+  if (root)
+    root_dev = grub_device_open(root);
+
+  if (!root_dev) {
     char **root_devices = grub_guess_root_devices (dir);
     char **cur;
     int found = 0;
@@ -263,6 +265,8 @@ setup (const char *dir,
 	char *drive;
 	grub_device_t try_dev;
 
+	if (root_dev)
+	  break;
 	drive = grub_util_get_grub_dev (*cur);
 	if (!drive)
 	  continue;
@@ -956,6 +960,8 @@ static struct argp_option options[] = {
    N_("install even if problems are detected"), 0},
   {"skip-fs-probe",'s',0,      0,
    N_("do not probe for filesystems in DEVICE"), 0},
+  {"root-device", 'r', N_("DEVICE"), 0,
+   N_("use DEVICE as the root device"), 0},
   {"verbose",     'v', 0,      0, N_("print verbose messages."), 0},
   {"allow-floppy", 'a', 0,      0,
    /* TRANSLATORS: The potential breakage isn't limited to floppies but it's
@@ -993,6 +999,7 @@ struct arguments
   char *core_file;
   char *dir;
   char *dev_map;
+  char *root_dev;
   int  force;
   int  fs_probe;
   int allow_floppy;
@@ -1040,6 +1047,13 @@ argp_parser (int key, char *arg, struct 
         arguments->dev_map = xstrdup (arg);
         break;
 
+      case 'r':
+        if (arguments->root_dev)
+          free (arguments->root_dev);
+
+        arguments->root_dev = xstrdup (arg);
+        break;
+
       case 'f':
         arguments->force = 1;
         break;
@@ -1172,7 +1186,7 @@ main (int argc, char *argv[])
   setup (arguments.dir ? : DEFAULT_DIRECTORY,
 	 arguments.boot_file ? : DEFAULT_BOOT_FILE,
 	 arguments.core_file ? : DEFAULT_CORE_FILE,
-	 dest_dev, arguments.force,
+	 arguments.root_dev, dest_dev, arguments.force,
 	 arguments.fs_probe, arguments.allow_floppy);
 
   /* Free resources.  */