root@ubuntu:~# grub-install
install_device not specified.
Usage: grub-install [OPTION] install_device
Install GRUB on your drive.

  -h, --help              print this message and exit
  -v, --version           print the version information and exit
  --root-directory=DIR    install GRUB images under the directory DIR
                          instead of the root directory
  --grub-shell=FILE       use FILE as the grub shell
  --no-floppy             do not probe any floppy drive
  --force-lba             force GRUB to use LBA mode even for a buggy
                          BIOS
  --recheck               probe a device map even if it already exists

INSTALL_DEVICE can be a GRUB device name or a system device filename.

grub-install copies GRUB images into the DIR/boot directory specfied by
--root-directory, and uses the grub shell to install grub into the boot
sector.

Report bugs to <bug-grub@gnu.org>.
root@ubuntu:~# update-grub
Searching for GRUB installation directory ...
No GRUB directory found.
 To create a template run 'mkdir /boot/grub' first.
 To install grub, install it manually or try the 'grub-install' command.
 ### Warning, grub-install is used to change your MBR. ###