基本上 GRUB 只建議「有磁碟分割表且安裝在整個硬碟」的使用模式
在舊式 PC(MBR) 磁碟分割表下 core.img 被安裝在 MBR 與第一分區間的間隙(MBR gap)
The partition table format traditionally used on PC BIOS platforms is called the Master Boot Record (MBR) format; this is the format that allows up to four primary partitions and additional logical partitions. With this partition table format, there are two ways to install GRUB: it can be embedded in the area between the MBR and the first partition (called by various names, such as the "boot track", "MBR gap", or "embedding area", and which is usually at least 31 KiB), or the core image can be installed in a file system and a list of the blocks that make it up can be stored in the first sector of that partition.
Each of these has different problems. There is no way to reserve space in the embedding area with complete safety, and some proprietary software is known to use it to make it difficult for users to work around licensing restrictions; and systems are sometimes partitioned without leaving enough space before the first partition. On the other hand, installing to a filesystem means that GRUB is vulnerable to its blocks being moved around by filesystem features such as tail packing, or even by aggressive fsck implementations, so this approach is quite fragile; and this approach can only be used if the /boot filesystem is on the same disk that the BIOS boots from, so that GRUB does not have to rely on guessing BIOS drive numbers.
The GRUB development team generally recommends embedding GRUB before the first partition, unless you have special requirements. You must ensure that the first partition starts at least 31 KiB (63 sectors) from the start of the disk; on modern disks, it is often a performance advantage to align partitions on larger boundaries anyway, so the first partition might start 1 MiB from the start of the disk.