Modify grub to solve computer startup error: error 17

The original computer has C, D, e, F, G. C disk, windows system disk and G disk are installed with CentOS. Later, due to the need to compress the volume of the way from the D disk compressed out of an H disk. Then when I started the computer again, I encountered an error: error 17

The reason:
is that windows is installed first and then Linux is installed. In this way, grub is booted by CentOS on disk g. now a new logical partition is divided before the partition, which causes the disk system symbol to move backward by one bit. Therefore, grub fails.
Solution:
1, burn a Linux Installation U disk, enter BIOS, modify boot items, and boot from U disk.
2. I use RedHat 7.0. After the U disk is started, enter the troubleshooting option, and then enter the rescue a @ #% $%. Enter all the way to shell mode.
3. In shell mode, use fdisk – L to view all partitions of the computer, and find that the original CentOS partition is sdb9. Grub command enters grub, root (hd1,8) command specifies partition, setup (HD1) installs grub to corresponding partition, and quit grub.

At this time, boot the hard disk again, and you can already see grub. But only windows can start, CentOS will report error, error 17, cannot mount

4. Start the U disk again and enter the shell mode under rescue. Check the grub configuration file of Linux system to see if there is any problem. I have a look, and there is no problem.

#mkdir linux
#mount /dev/sdb9 linux
#cd linux
#cd grub
#vi grub.conf

5. Start the hard disk, enter grub interface, move the cursor to the startup option of Linux, press e key to modify the startup sequence. Change the root (hd0,7) option to root (hd0,8) and enter. It’s ready to start.

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