How to recovery MBR

For raid :


1. The following is how to create Ubuntu live USB: 

http://blog.xuite.net/yh96301/blog/57645340-%E5%85%8D%E8%B2%BB%E8%A3%BD%E4%BD%9CUbuntu+Live+USB%E9%96%8B%E6%A9%9F%E9%9A%A8%E8%BA%AB%E7%A2%9F%E7%9A%84%E8%BB%9F%E9%AB%94unetbootin


2. check the raid device id :

When "df -h", will see the following raid partitions: 

/dev/mapper/isw_dcgajhgdje_Volume0p1 (/)
/dev/mapper/isw_dcgajhgdje_Volume0p5 (/home)

The "/dev/mapper/isw_dcgajhgdje_Volume0" is raid id.

3. After enter Ubuntu live USB:


mkdir /mnt/sda

mount  /dev/mapper/isw_dcgajhgdje_Volume0p1 /mnt/sda
mount --bind /proc /mnt/sda/proc
mount --bind /dev /mnt/sda/dev

chroot /mnt/sda
grub-install /dev/mapper/isw_dcgajhgdje_Volume0p