grub-set-default.real --version (return code: 0)
grub-set-default.real (GRUB) 2.02~beta2-36ubuntu3.7
grub-set-default.real --help (return code: 0)
Usage: grub-set-default.real [OPTION] MENU_ENTRY
Set the default boot menu entry for GRUB.
This requires setting GRUB_DEFAULT=saved in /etc/default/grub.
-h, --help print this message and exit
-v, --version print the version information and exit
--boot-directory=DIR expect GRUB images under the directory DIR/grub
instead of the /boot/grub directory
MENU_ENTRY is a number, a menu item title or a menu item identifier.
Report bugs to <bug-grub@gnu.org>.