Centos repair grub boot tutorial

Sometimes we use a USB flash drive to install centos, and accidentally install grub to the USB flash drive. as a result, the boot needs to be inserted into the USB flash drive to start the server, or grub is damaged. in this case, we need to re-install grub to the hard disk. The following describes several repair or installation methods for installing grub. Method 1: Specify/boot partition 1. grub & gt; root (hd0, 0) if you are not sure which partition/boot is in, use grub & gt; sometimes we use a USB flash drive to install centos and accidentally install grub to a USB flash drive, as a result, you need to insert a USB flash drive to boot the server, or grub is damaged. in this case, you need to reinstall grub to the hard disk. Several repair or installation methods are introduced downstairs
Install grub method 1
Specify/boot partition
1. grub> root (hd0, 0)
If you are not sure which partition/boot is in, use the grub> find/boot/grub/stage1 command to find out
1) install grub to the MBR on the first hard disk.
Grub> setup (hd0)
2) install grub to the boot sector in the first partition of the first hard disk
Grub> setup (hd0, 0)

Install grub method 2
# Grub-install -- root-directory =/boot/dev/hda