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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SETPNP(8)						      System Manager's Manual							 SETPNP(8)

NAME
setpnp - modify Plug and Play BIOS device resources SYNOPSIS
setpnp [-b] device resource... setpnp [-b] device {on|off} DESCRIPTION
This utility updates the system resource information for Plug and Play BIOS device nodes. A device is specified by its two-digit hex node number. In its first form, a list of resources are given on the command line. Alternatively, a device can either be simply switched ``on'' (reset to its boot configuration) or ``off'' (all resources disabled). There are four types of resources: ``io'', ``mem'', ``irq'', and ``dma''. A resource list consists of one or more space-separated pairs of a resource type with one or more values. Multiple values for one resource type can be separated by commas. Values can also either be uni- tary or dash-separated ranges. For example: setpnp 0d io 0x2f8-0x2ff irq 3 setpnp 12 io 0x350-0x35f,0x2f8-0x2ff irq 3 irq 10 setpnp 0b irq off The order of items of different types is not important, but if more than one item of the same type is present, their relative order is sig- nificant. The Plug and Play BIOS will reject invalid configuration attempts; however, setpnp will not attempt to determine why a configu- ration was rejected. By default, current (dynamic) device configuration information is modified. With the -b option, a device's boot (static) configuration can be updated. Some devices may only be reconfigured for the following boot. Be especially careful when modifying your system's boot config- uration. Improper use of this command may disable vital system devices and render your system unbootable. OPTIONS
-b Boot mode: update the device resource information that will be used at next boot (as opposed to current resource info). FILES /proc/bus/pnp/... The kernel interface for Plug and Play BIOS device services. AUTHORS
David Hinds - dahinds@users.sourceforge.net SEE ALSO
lspnp(8) pcmcia-cs 2001/10/04 03:11:23 SETPNP(8)