Bootloader: Difference between revisions

The easiest way to boot another OS is a mechanism called chainloading. Windows stores something akin to a second-stage bootloader in the boot sector of the partition it was installed in. When installing Linux, writing e.g. LILO or GRUB to the partition boot sector instead of the MBR is also an option. Now, the thing your MBR bootsector can do is to relocate itself (copying from 0x07c0:0x0000:0x7c00 to, traditionally, 0x0060:0x0000), parse the partition table, display some kind of menu and let the user chose which partition to boot from. Then, your (relocated) MBR bootsector would load that partition boot sector to 0x07c0:0x0000:0x7c00, and jump there. The partition boot sector would be none the wiser that there already was a bootsector loaded before, and could actually load yet another bootsector - which is why it's called chainloading.