/usr/sbin/grub-probe: error: cannot find a device for /boot/grub (is /dev mounted?).
ubuntu@ubuntu:~$ sudo grub-install --root-directory=/mnt /dev/sda6
/usr/sbin/grub-setup: warn: Attempting to install GRUB to a partition instead of the MBR.  This is a BAD idea..
/usr/sbin/grub-setup: warn: 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-setup: error: if you really want blocklists, use --force.