recover grub2 use liveCD

The linux partition is /dev/sda6.
first,boot the liveCD.
then,open the terminal,and type this line:


sudo mount /dev/sda6 /mnt
sudo mount --bind /dev/ /mnt/dev
sudo chroot /mnt
update-grub
grub-install --recheck /dev/sda
sudo umount /mnt
sudo umount /mnt/dev