MBR as a constant

[Brian McKee]

On Mon, Apr 6, 2009 at 12:38 PM, Allen Meyers <texas.chef94 at gmail.com> wrote:
> The subject title is really not as descriptive as it should be, but here goes.
> Most windows/Linux users have windows first with the MBR as a constant
> I guess. I on the other hand have no windows but 8.10 is my constant
> (I thought) on sda. Debian is sdb on external.
> My question is when I upgrade to 9.04 on sda1 does MBR as a matter of
> course load with it into my internal HD?
> Like when I loaded Debian the question was asked as 2 drives were
> detected where to put grub MBR or?
> I know this sounds confused, but I just wanted it spelled out because
> the OS on my HD is not a constant and I am windowless

Let me see if this makes any more sense to you.

The BIOS is told which device to look at first to boot.

If it's a hard drive, it goes to the very first track and pulls off
exactly 512 bytes.  That 512 bytes has just enough code to tell it
where to go to find a boot loading program like GRUB or winboot (or
whatever MS calls it - I'm drawing a blank)

That 512 bytes is called the Master Boot Record.

Now, there is absolutely nothing tying it to the rest of that disk -
it could easily enough say 'go get GRUB from the third SCSI drive' or
the USB key or whatever.

So it's BIOS -> MBR -> GRUB -> Operating System  - each independent of
each other.

Because most BIOSs are set to boot off of the Primary Master IDE
drive, most people use the MBR of that drive to point to GRUB.

Does that make it more clear?

Brian