Ubuntu system Grub failure how to do

What should I do if the Ubuntu system Grub fails? Many computer users think of reloading: Grub, however, after reloading, it means that the original system saved data is gone, I believe it will It causes a lot of trouble for the use of computer users. In fact, there is a simpler and faster way to solve the problem of the failure of the Ubuntu system Grub, that is to repair the Grub, can retain the original settings, but also minimize the impact.
Ubuntu
How does the Ubuntu system fix Grub?
1. Find a way to get into Ubuntu's Live CD system, or other newer versions of the Live CD system.
2. Open the terminal, enter sudo fdisk -l, view the partition with ID=83, and record sd[NUM], such as sda8.
3. If there are multiple partitions with ID=83 in the previous step, I will try to determine the partition number where the partition is located, and /boot is also mounted on the same partition as the /partition, for example, sda8.
4. Enter sudo -i and get root privileges.
5.mkdir /media/tmp.
6. Mount the /partition to the newly created directory mount /dev/sda8 /media/tmp.
7. If the previous system /boot is mounted separately, you need to find the /boot partition such as sda7, then mount /dev/sda7 /media/tmp/boot. Otherwise this step jumps directly.
8. Next, prepare to install grub, terminal input: grub-install --root-directory=/media/tmp /dev/sda.
9. If you see the message Installation finished, no error occured like the show has been a success.
10. At this time, restart the system, you should be able to see the original grub2 boot interface back, and if there are other systems, it will also display the list of startup items
PS: If you do not see step10 Windows 8 startup items, after the normal startup of Ubuntu, the terminal enters sudo update-grub2, after which you should wait for a moment to see that Windows 8 startup items are also added to the list.