On Tuesday, 7 October at 09:47, Hendrik Boom wrote:
>(...)>
>Isn't there another piece of bootloader outside the file system at
> the very beginning of the boot disk?
> Especially if using lilo?
>And isn't there a DOS partition that's used by the new-fangled bootup
> system that replaced legacy boot and that the Wintel copanies have
> imposed on us? I've never figured out where its content is supposed
> to come from.
>
>-- hendrik

Originally, the BIOS bootloader was in the first 512 bytes of the boot
disk - the Master Boot Record or boot sector. These days, bootloaders
are bigger (and more complicated) so grub has an initial image which is
witten to the boot sector, which then passes control to a bigger and
more complicated image which is usually written to an unformatted
partition. This is then able to read your filesystem, load the main part
of grub, your grub.conf and so on.

I don't know how lilo works exactly, except that the configuration is
compiled right into the boot image. If anyone knows better, feel free to
correct me.

As for the new-fangled bootup system, the machine's firmware does indeed
boot straight into a dedicated partition which, essentially, contains a
simple operating system (the UEFI). As I understand it, this contains
one or more programs which each act as the bootloader to their own OS
(if running Wintendo) or can, on a more enlightened system, chainload
into other things (such as grub or the linux kernel directly).

The whole thing is, of course, more complicated if you want to get into
the details, but that's the short version.

- Antoine

--
All fungi are edible.
Some are only edible once.