Grub

Tim ignored_mailbox at yahoo.com.au
Mon Aug 20 05:33:33 UTC 2007


Chris Jones:
>> you have it the wrong way around. grub uses the bios, the bios knows nothing 
>> about grub (or any bootloader).

Karl Larsen:
> Not correct. Grub never runs in a boot sequense it is read by BIOS 
> that should find the kernel and start it if it works.

Grossly simplified:  The computer starts up (or restarts), runs the
program in the BIOS, it does its checks, and other things, then looks
for bootable media, reads the bootblock, and loads the instructions
found in it.  In our case, the first thing to do is to make use of GRUB.
Now GRUB *uses* the *BIOS* to further access the drive, to load the rest
of itself [1], then the operating system.  When the OS starts booting,
it takes over.

1:  The complexity of what GRUB provides is too big to fit in the
standard bootblock, and is bigger than most BIOS's space, too.  So this
sort of thing (extensive boot menus, drive remapping to overcome other
limitations, etc.) can't generally be done by the motherboard, either.

-- 
[tim at bigblack ~]$ uname -ipr
2.6.22.1-41.fc7 i686 i386

Using FC 4, 5, 6 & 7, plus CentOS 5.  Today, it's FC7.

Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.






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