MBR and Boot Process

rm_rib · 26. Nov 2010, 02:18 PM

Just for information on Macrium MBR defaults, in case someone is interested:

It seems like Macrium Free always is backing up the MBR in the image.
But one is left with 3 options when restoring the image to a HDD:

1. Do not replace.
2. Replace with the MBR from the backup (Recommended)
3. Replace with the standard XP MBR
---
3. Might be handy in case of a virus contamination, but unfortunately I don't know if XP and Vista MBR are the same. Anyone?

A nice weekend to all!

Jojoyee · 26. Nov 2010, 02:38 PM

Quote:

Originally Posted by rm_rib

...but unfortunately I don't know if XP and Vista MBR are the same. Anyone?

This article might help. It mentions about the boot process and elaborates on the MBR, PBR and so on.

rm_rib · 26. Nov 2010, 03:15 PM

Thank you very much, this article seems to be very good - a bit on the depth.
I have just skimmed it and can already see that the XP and the Vista MBR definately are not the same.

Could it be that the Macrium update designers have "forgotten" to update the text? Doesn't seem likely. Could it be that Vista is supposed to "repair" the MBR to an actual Vista state? Possibly dangerous to trust that.

The article is suggesting that it could be wise to make a "floppy" with a functional Vista MBR. Maybe not such a bad idea.

A lot to think about on a dark november evening.

Thank you for the guidance to this article - I certainly shall read it more thoroughly now.

rm_rib · 26. Nov 2010, 10:09 PM

Continuation...

Having read the article recommended by Jojoyee, I now understand how much I have been mixing up things before. For instance it was of course not the MBR that could reside on a "floppy"/CD, it was a Boot Manager - and that still looks like maybe a good idea.

I now understand that the MBR is non OS specific, while the Vista Partition Boot Record of course is Vista-specific.

So, provided the part of the MBR that is the Partition Table is also non OS-specific, it makes sense that the MBR mentioned in Macriums image recovery option #3, and is named XP MBR, can be used even for Vista recovery.

But:
Why is it named XP MBR then? And not just MBR?
Maybe just to exclude Windows versions prior to XP?
Or does the Partition Table on a MBR level differ between XP and Vista after all?
Any other reason?
Anybody knows?

Sorry to be a pain - I'm probably too curious

Jojoyee · 27. Nov 2010, 01:07 AM

Quote:

Originally Posted by rm_rib

Why is it named XP MBR then? And not just MBR?
Maybe just to exclude Windows versions prior to XP?
Or does the Partition Table on a MBR level differ between XP and Vista after all?
Any other reason?
Anybody knows?

I'd have the same queries if that term is used.

On a more technical note, the MBR is a small bit of software of only 512 bytes in length located in the first sector of a hard disk. Among others, it contains a code area and a table of primary partitions (max 4). Typically, when the code is run, it finds an active partition defined in the table, then loads and runs the PBR (aka VBR) for that partition. See Structure of MBR.

As mentioned the MBR is non-OS specific, so using such terms as XP MBR (or Win7 MBR, Ubuntu MBR...) can be confusing. I could be wrong since I've not read the original context what that term implies. It might mean that the MBR has been updated after installing the XP system. To me the best is to avoid using such term. I can have a PC multi-booting XP, Win7 and Ubuntu and use EasyBCD to re-write MBR at a certain time after editing some boot entries. 'Which' MBR is it then?

rm_rib · 27. Nov 2010, 10:29 AM

Hi Jojoyee, thanks for your answer - I tried to attach a screen dump to show the exact text in Macrium's options display but the max size was to small for an acceptable quality.

Thanks for the link too - it's getting hardcore now, at least for my level - but that's good, it might help the understanding.

I'll load a couple of cappucinos and read it - slowly!

Thanks again!

rm_rib · 27. Nov 2010, 10:52 PM

Continuation...

I have now studied the MBR structure according to Jojoyee's recommendation. It was rather tough - at my level! Not to understand all the details, but to grasp it as a whole - assemble all the details into a manageable model.
And it got more and more interesting, detailed and off topic.

The purpose was to get an answer to the question: are there any details in the MBR that could make it suspect as some kind of OS specific?

The answer is: probably not. Given that I have understood it all right, and within this article's limits. One could most probably drill deeper, but this satisfies my curiosity.

So Macrium's "XP MBR" is just a MBR - as far as I'm concerned at this point.

Jojoyee, this was good information, thank you for leading me to it!

Jojoyee · 28. Nov 2010, 01:11 AM

You're welcome rm_rib. It's an interesting subject as most average users including me expect the PC just has to work out of the box, but when the MBR is pointing to nowhere for some reasons, it becomes a great concern since the PC cannot run at all.

The 'confusing' term "XP MBR" could simply mean the MBR is pointing to a VBR in an XP partition to boot up the system, but you're right it's just an MBR.

For general understanding, when a PC is turned on, the computer's BIOS on the motherboard finds the MBR sector of a harddisk and passes control to it, the code inside the MBR finds the active partition and passes control to the VBR of that partition. Depending on the setup, the BIOS can also first look for a LiveCD to boot up the system from a CD/DVD drive, useful when the MBR doesn't work or the VBR is corrupted and the PC cannot boot into a system on the harddisk.

In a multi-booting setup which I'm using, the MBR contains "GRUB stage 1". When run, the "GRUB stage 1" passes control to the "GRUB stage 2" residing in a partition to present a multi-boot menu for me to choose either booting into XP, Win7, Ubuntu or Peppermint.

Hmmm... while writing this post, I finished a cup of cappuccino.

See also: Boot Process with Grub.

crank · 28. Nov 2010, 11:08 AM

Quote:

Originally Posted by Jojoyee

This article might help. It mentions about the boot process and elaborates on the MBR, PBR and so on.

Thought I would chime in here with a second on this link, the Multibooters pages are, at least for me, the best source I have found so far for booting windows Vista+. It has the right amount of tech, is well and very efficiently written and illustrated, lays out all the pitfalls you need to know about and so avoid. Let me let the author express it with a wry twist that slips in his writing occasionally:

Quote:

I have learned from experience that most people will consider the computer boot sequence as something that is almost beyond their comprehension. Many guides or examinations are often overly technical and will just confuse the issue even further, or sap the reader's will to live. This guide will try to explain only what you really need to know.

rm_rib · 28. Nov 2010, 12:19 PM

Hi Jojoyee, happy sunday and nice cappuccinos!

About the confusing term "XP MBR": If the MBR should be pointing to anything in an XP partition, so where would that partition come from? I don't have one - on this machine anyway. But maybe the person who wrote the words had one, and it just slipped his mind, and he wrote it wrong? That's human.

The positive here is that it lead to some examining, and for me to a better understanding of the boot process. That's nice.

About dual/multi booting: this is interesting for me too, as I plan to add Linux, probably Ubuntu. So, according to the Multibooter page, there will be a decision to make, as where to put the Grub. Entirely in the Linux part is recommended there - if I remember and understand it right - to keep things clean and recoverable.

But maybe a new thread would be needed, not to get off topic?

26. Nov 2010, 02:18 PM	#1 (permalink)
rm_rib Member Join Date: Nov 2010 Posts: 27	MBR and Boot Process Just for information on Macrium MBR defaults, in case someone is interested: It seems like Macrium Free always is backing up the MBR in the image. But one is left with 3 options when restoring the image to a HDD: 1. Do not replace. 2. Replace with the MBR from the backup (Recommended) 3. Replace with the standard XP MBR --- 3. Might be handy in case of a virus contamination, but unfortunately I don't know if XP and Vista MBR are the same. Anyone? A nice weekend to all!

28. Nov 2010, 01:11 AM	#8 (permalink)
Jojoyee Maestro di Search Join Date: Jul 2008 Posts: 4,295	You're welcome rm_rib. It's an interesting subject as most average users including me expect the PC just has to work out of the box, but when the MBR is pointing to nowhere for some reasons, it becomes a great concern since the PC cannot run at all. The 'confusing' term "XP MBR" could simply mean the MBR is pointing to a VBR in an XP partition to boot up the system, but you're right it's just an MBR. For general understanding, when a PC is turned on, the computer's BIOS on the motherboard finds the MBR sector of a harddisk and passes control to it, the code inside the MBR finds the active partition and passes control to the VBR of that partition. Depending on the setup, the BIOS can also first look for a LiveCD to boot up the system from a CD/DVD drive, useful when the MBR doesn't work or the VBR is corrupted and the PC cannot boot into a system on the harddisk. In a multi-booting setup which I'm using, the MBR contains "GRUB stage 1". When run, the "GRUB stage 1" passes control to the "GRUB stage 2" residing in a partition to present a multi-boot menu for me to choose either booting into XP, Win7, Ubuntu or Peppermint. Hmmm... while writing this post, I finished a cup of cappuccino. See also: Boot Process with Grub. __________________ Keep It Short and Sweet Last edited by Jojoyee; 28. Nov 2010 at 10:34 AM. Reason: Edited "When run...."

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26. Nov 2010, 03:15 PM	#3 (permalink)
rm_rib Member Join Date: Nov 2010 Posts: 27	Thank you very much, this article seems to be very good - a bit on the depth. I have just skimmed it and can already see that the XP and the Vista MBR definately are not the same. Could it be that the Macrium update designers have "forgotten" to update the text? Doesn't seem likely. Could it be that Vista is supposed to "repair" the MBR to an actual Vista state? Possibly dangerous to trust that. The article is suggesting that it could be wise to make a "floppy" with a functional Vista MBR. Maybe not such a bad idea. A lot to think about on a dark november evening. Thank you for the guidance to this article - I certainly shall read it more thoroughly now.

26. Nov 2010, 10:09 PM	#4 (permalink)
rm_rib Member Join Date: Nov 2010 Posts: 27	Continuation... Having read the article recommended by Jojoyee, I now understand how much I have been mixing up things before. For instance it was of course not the MBR that could reside on a "floppy"/CD, it was a Boot Manager - and that still looks like maybe a good idea. I now understand that the MBR is non OS specific, while the Vista Partition Boot Record of course is Vista-specific. So, provided the part of the MBR that is the Partition Table is also non OS-specific, it makes sense that the MBR mentioned in Macriums image recovery option #3, and is named XP MBR, can be used even for Vista recovery. But: Why is it named XP MBR then? And not just MBR? Maybe just to exclude Windows versions prior to XP? Or does the Partition Table on a MBR level differ between XP and Vista after all? Any other reason? Anybody knows? Sorry to be a pain - I'm probably too curious

27. Nov 2010, 10:29 AM	#6 (permalink)
rm_rib Member Join Date: Nov 2010 Posts: 27	Hi Jojoyee, thanks for your answer - I tried to attach a screen dump to show the exact text in Macrium's options display but the max size was to small for an acceptable quality. Thanks for the link too - it's getting hardcore now, at least for my level - but that's good, it might help the understanding. I'll load a couple of cappucinos and read it - slowly! Thanks again!

27. Nov 2010, 10:52 PM	#7 (permalink)
rm_rib Member Join Date: Nov 2010 Posts: 27	Continuation... I have now studied the MBR structure according to Jojoyee's recommendation. It was rather tough - at my level! Not to understand all the details, but to grasp it as a whole - assemble all the details into a manageable model. And it got more and more interesting, detailed and off topic. The purpose was to get an answer to the question: are there any details in the MBR that could make it suspect as some kind of OS specific? The answer is: probably not. Given that I have understood it all right, and within this article's limits. One could most probably drill deeper, but this satisfies my curiosity. So Macrium's "XP MBR" is just a MBR - as far as I'm concerned at this point. Jojoyee, this was good information, thank you for leading me to it!

28. Nov 2010, 12:19 PM	#10 (permalink)
rm_rib Member Join Date: Nov 2010 Posts: 27	Hi Jojoyee, happy sunday and nice cappuccinos! About the confusing term "XP MBR": If the MBR should be pointing to anything in an XP partition, so where would that partition come from? I don't have one - on this machine anyway. But maybe the person who wrote the words had one, and it just slipped his mind, and he wrote it wrong? That's human. The positive here is that it lead to some examining, and for me to a better understanding of the boot process. That's nice. About dual/multi booting: this is interesting for me too, as I plan to add Linux, probably Ubuntu. So, according to the Multibooter page, there will be a decision to make, as where to put the Grub. Entirely in the Linux part is recommended there - if I remember and understand it right - to keep things clean and recoverable. But maybe a new thread would be needed, not to get off topic?