reinstall f*cking grub after f*cking upgrade , not so frequently

1. boot using systemrescuecd
2. mount the localdisk , you can find all disks usingfdisk -l
3. now add system mount ( /dev and /sys ) on the mounted disk
mount --bind /dev /mnt/dev &&
mount --bind /dev/pts /mnt/dev/pts &&
mount --bind /proc /mnt/proc &&
mount --bind /sys /mnt/sys
4. chroot in the partition% chroot /mnt/linux /bin/bash
5. install grub grub-install -root-directory=/mnt/ /dev/sdX
6. umount everything to reboot the rescue system
   umount /mnt/sys &&
umount /mnt/proc &&
umount /mnt/dev/pts &&
umount /mnt/dev &&
umount /mnt
7. reboot