Joe composed on 2016-08-01 20:15 (UTC+0100):
Installing the bootloader somewhere other than the MBR is useful if you dual-boot with Windows,
And if you multiboot with >2. Every installation cannot own a single MBR. Better that none do, so that potential for conflict is entirely avoided[1]. Windows bootloaders can "chainload" Grub little differently than Grub can load Windows' bootloader.
as the Windows bootloader *must* be in the MBR and it can execute another bootloader at the beginning of a partition. Oh, yes, it's only Windows which requires the partition 'bootable' flag to be set...
That was inherited from DOS, so DOS requires it too. And before Windows, OS/2 too inherited it from DOS, and since OS/2 has successors, e.g. eComStation, they all require it, and require it on one and only primary partition, and on at least one BIOS HD. If a Linux tool sets the flag on more than one primary, it's created a cannot boot DOS/Win/OS2 configuration.
OS/2's MBR code is nominally different from Windows, but Windows' installers accept it and will not overwrite it as they will when they find the totally alien Grub code there.
[1] http://old-en.opensuse.org/Bugs/grub#How_does_a_PC_boot_.2F_How_can_I_set_up_a_working_GRUB.3F
-- "The wise are known for their understanding, and pleasant words are persuasive." Proverbs 16:21 (New Living Translation) Team OS/2 ** Reg. Linux User #211409 ** a11y rocks! Felix Miata *** http://fm.no-ip.com/