xubuntu@xubuntu:~$ sudo grub-install --boot-directory=/mnt/boot /dev/sda3
/usr/sbin/grub-bios-setup: warning: File system `ext2' doesn't support embedding.
/usr/sbin/grub-bios-setup: warning: Embedding is not possible.  GRUB can only be installed in this setup by using blocklists.  However, blocklists are UNRELIABLE and their use is discouraged..
/usr/sbin/grub-bios-setup: error: will not proceed with blocklists.