Recover Grub2 Bootloader in XUbuntu

1. Boot with Xubuntu Live CD
2. In a xfce4-terminal:

Create a mount point
# sudo mkdir /media/xubuntu

Mount your root partition somewhere, my root partition is sda2
# sudo mount /dev/sda2 /media/xubuntu

Mount proc and dev
# sudo mount -t proc none /media/xubuntu/proc
# sudo mount -o bind /dev /media/xubuntu/dev

chroot to your system
# sudo chroot /media/xubuntu

Re-install grub2
# grub-install

Done! reboot and enjoy.