Two approaches to this. The first is to use the grub-install utility:
grub-install --root-directory=/boot /dev/???
The second approach is to use the grub command line:
1. Start the grub command line:
grub
2. Determine the boot device:
find /boot/grub/stage1
You’ll get something like “(hd0,0)”.
3. Tell grub where the root is:
root (hd0,0)
4. Install the MBR:
setup (hd0,0)
