Have I understood?

Yann Droneaud ydroneaud at opteya.com
Fri Jan 11 12:42:14 EST 2013

> Hello everybody,
> I am tracing the boot kernel process
> (http://tldp.org/HOWTO/Linux-i386-Boot-Code-HOWTO) and I have a
> question: GNU/GRUB loads vmlinuz at 0x7c00 memory, does not it? And
> then, the first instruction CPU executes is in bootsec.S, does not it?
> Have I understood well?

The PC BIOS load and execute the first 512 bytes of a Linux kernel (eg
bootsect.S) when the kernel was dumped on a floppy disk.

The so called boot sector was loaded a 0x7c00 and in charge of loading the
whole kernel in memory. Then it ran the setup code before transfering
control to the kernel.
[who use this today ... with kernel far bigger than 1.44MBytes
 btw, bootsect.S is no more included in the kernel.
 Floppy booting rely on syslinux]

A boot loader such as Lilo and GRUB load the kernel image in memory and
transfer control to the setup code.


Yann Droneaud

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