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I'm trying to understand a system boot process. Am i right with the following statements:?

  1. MBR boot loader code is absolutely operating system independent and is written when one create the first partition on a disk using for e.g. DOS format or Linux fdisk /cfdisk commands.
  2. Just after partitioning there is no VBR (Volume Boot Record) yet. It is created only after the specific system installation because it contains system specific boot code.

Can someone ensure

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  1. No.

MBR code can be anything. As pointed out by Martin is his answer and as suggested in your other question regarding the topic the MBR contains a section that has the bootstrap code. As it is an arbitrary section it can contain any form of code. It could be empty, it could be code that displays a funny message or a whole bootloader.

Consider GRUB which is a common bootloader. Just for some graphic representation from the GRUB Wiki article take this Image by ScotXW:

GRUB Bootloading Process by ScotXW

As you can see it's a multi stage process but the initial boot.img would be specific to GRUB. The subtitle of that image states (which is also visible in the image):

GNU GRUB on a MBR-partitioned hard drive; stage 1 (boot.img) can alternatively be written into one of the VBRs.

So the code in that particular memory location is generic enough/smart enough to not be dependent to be in the MBR bootstrap location but instead can also be in a VBR. Yet it would still be very different from what e.g. the Windows boot loader looks like. With modern security and everything it's becoming more common to have those chain loaders.

  1. Maybe. If you look at this it would suggest that it's just a name for the first sector of a volume. As such each volume would have a VBR after creation.
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For 1 you're not entirely correct, MBR is independant of any OS. It is present on a disk. But MBR Boat loader is some code contained in the MBR, actually the Bootstrap Code, and can be modified as it mainly contains the path to the file that will be loaded next in the boot process.

I suggest the reading of the following article to get a detailed view of a computer boot process.

For 2, this is not what I understand from Wikipedia :

On partitioned devices, it is the first sector of an individual partition on the device, with the first sector of the entire device being a Master Boot Record (MBR) containing the partition table.

What I understand from this is that MBR is the first sector of a device while VBR is the first sector of a partition.

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  • The bit about MBR and VBR are correct. – Seth Nov 25 '16 at 13:22

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