If you see a screen like this:
┌──────────────────────────────────────┤ Configuring grub-pc ├───────────────────────────────────────┐ │ The GRUB boot loader was previously installed to a disk that is no longer present, or whose │ │ unique identifier has changed for some reason. It is important to make sure that the installed │ │ GRUB core image stays in sync with GRUB modules and grub.cfg. Please check again to make sure │ │ that GRUB is written to the appropriate boot devices. │ │ │ │ If you're unsure which drive is designated as boot drive by your BIOS, it is often a good idea to │ │ install GRUB to all of them. │ │ │ │ Note: it is possible to install GRUB to partition boot records as well, and some appropriate │ │ partitions are offered here. However, this forces GRUB to use the blocklist mechanism, which │ │ makes it less reliable, and therefore is not recommended. │ │ │ │ GRUB install devices: │ │ │ │ [ ] /dev/sda (53687 MB; VBOX_HARDDISK) │ │ [ ] - /dev/sda1 (999 MB; /boot) │ │ [ ] /dev/dm-0 (9999 MB; vg00-lvroot) │ │ │ │ │ │ <Ok> │ │ │ └────────────────────────────────────────────────────────────────────────────────────────────────────┘
The right option id the first one
/dev/sda (53687 MB; VBOX_HARDDISK), because it is the hard disk in which the /root partition is installed.
Installing grub in a partition (e.g. choosing the second option) is advised against:
(http://askubuntu.com/questions/19704/bad-idea-warning-when-trying-to-recover-grub-after-windows-removed-it) - The master boot record, MBR, is the first 512 byte 'sector' of any partitioned hard disk. - The BIOS searches this sector when trying to find a device it can boot from. - In the GNU/Linux system, your hard disks are all named /dev/sd[x], where x are consecutive letters. E.g.: /dev/sda and /dev/sdb. The first partition on the first disk is called /dev/sda1. The fourth partition on the seventh hard disk is called /dev/sdg4, and so on. At the very least, you'll have one partition. - These partitions are not searched for bootable data by the bios. As a result, grub-install [...] /dev/sda7 will issue a warning. You can install it there, but in almost any case, you shouldn't.