Restart Ubuntu after Win8 or Win7 is reinstalled.

Recently, a consumer preview version of Windows 8 was launched. The original system is win7 + ubuntu11.10 dual system, ubuntu is a direct hard disk installed on the G disk, the default grub is used for guidance. After installing win8, it covered the startup items of ubuntu, so I searched the internet for the solution. The procedure is as follows:
 
Find a ubuntu Cd (not limited version, 11.04 or above is the best, I use 11.04 disk, because 11.10 disk does not know where to go), and then change the system to start from the CD, go to the temporary ubuntu system and select "Try ubuntu ".
Run the command: sudo fdisk-l (here it is not the number 1, it is the letter l), find the ubuntu partition. Because I mounted the G disk, it is displayed as sda8.
Run the command: sudo-I to enter the root user to facilitate subsequent operations.
Run the command mkdir/media/tmpdir to create a temporary folder, and then enter the command: mount/dev/sda8/media/tmpdir to mount the system.
Next is the most important step. Enter the command: sudo grub-install -- root-directory =/media/tmpdir/dev/sda (note that this is sda, which should not be written as sda8 ), if no error report is displayed, the operation is successful.
Next, restart the system, do not enter windows, first enter ubuntu, enter the command in the terminal: sudo update-grub2 update grub after successful completion, this time you can restart to enter any system.
The above has passed the Windows 7 and Windows 8 system tests, and finally solved the startup Item problem perfectly.