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What Does Happen During Boot Process? - BIOS and MBR

 
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Old 12-11-2009
What Does Happen During Boot Process? - BIOS and MBR
I'm talking about boot process in multi-boot Linux perceptive.

Please tell me whether my explanation is right or wrong? If wrong, please explain.

"The BIOS checks the system and loads this initial bootstrapping code into
memory. This initial bootstrap code searches for an active partition and looks for a first sector of that active partition.

After that, bootstrap code gets whatever boot code (usually GRUB Stage 1) in the VBR and loads it in memory, so GRUB Stage 1 in this case overrides the MBR initial bootstrap that's in memory.

Once GRUB Stage 1 is in memory, it takes GRUB Stage 2 from /boot/ and loads it memory. Thus, GRUB Stage 2 overrides the GRUB Stage 1.

Now once GRUB Stage 2 is in memory, it presents an interface where the user
can select which OS to boot.

Once OS is selected, the GRUB stage 2 loads the selected Kernel into Memory, so the chosen OS Kernel overrides GRUB Stage 2.

Now this Kernel has the control and finishes the process. "

Thanks!
 
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LEARN ABOUT CENTOS

grub2-bios-setup

GRUB-BIOS-SETUP(3)					     Library Functions Manual						GRUB-BIOS-SETUP(3)

NAME

       grub-bios-setup -- Set up images to boot from a device.

SYNOPSIS

       grub-bios-setup [-a | --allow-floppy] [-b | --boot-image=FILE]
			[-c | --core-image=FILE] [-d | --directory=DIR]
			[-f | --force] [-m | --device-map=FILE]
			[-s | --skip-fs-probe] [-v | --verbose] DEVICE

DESCRIPTION

       You should not normally run this program directly.  Use grub-install instead.

OPTIONS

       --allow-floppy
	      Make  the device also bootable as a floppy.  This option is the default for /dev/fdX devices.  Some BIOSes will not boot images cre-
	      ated with this option.

       --boot-image=FILE
	      Use FILE as the boot image.  The default value is boot.img.

       --core-image=FILE
	      Use FILE as ther core image.  The default value is core.img.

       --directory=DIR
	      Use GRUB files in the directory DIR.  The default value is /boot/grub.

       --force
	      Install even if problems are detected.

       --device-map=FILE
	      Use FILE as the device map.  The default value is /boot/grub/device.map .

       --skip-fs-probe
	      Do not probe DEVICE for filesystems.

       --verbose
	      Print verbose messages.

SEE ALSO

       info grub

								  Wed Feb 26 2014						GRUB-BIOS-SETUP(3)