Dell MBR backup

Discussion in 'Dell' started by Michael B. Trausch, Oct 27, 2008.

  1. Does anyone here have a newer Dell laptop that utilizes a recovery
    partition? I am finding myself in need of a copy of the code segment
    of the MBR for such a machine to restore it after XP gunked it up
    without having first taken a backup. The purpose of the custom code in
    the Dell MBR is to kick-start the recovery process by carrying out some
    modifications to the partition table and then starting the recovery
    boot process.

    If someone does have such a laptop, could they please send me a private
    email with a hex dump of the MBR (sector 0, 512 bytes from the hard
    drive)? That way, I can extract the MBR code section and overlay it on
    the Dell laptop we have to re-enable the system restore functionality.
    It'd be much appreciated, thanks!

    --- Mike
     
    Michael B. Trausch, Oct 27, 2008
    #1
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  2. Michael B. Trausch

    Daddy Guest

    I didn't know that Windows XP could access the master boot record, let
    alone 'gunk it up' all by itself.

    Given the wide variety of disk geometries in Dell's computers, I think
    you need to ask Dell for help with your specific model.

    Daddy
     
    Daddy, Oct 27, 2008
    #2
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  3. Installing XP can wipe the code segment clean with a Microsoft
    "standard" MBR. This is what happened in this case. Being that this
    was unintended, my expression that it gunked it up was merely a
    dysphymism.
    The part of the MBR that I am asking for is agnostic to geometries in
    that it has all the geometry information it needs with the partition
    table, which is read into BIOS along with the MBR before the MBR code
    is executed by the processor. (It only does this, of course, when the
    MBR has a valid signature in the last two bytes of the MBR.)

    From there, the MBR determines how to boot. Since the partition table
    is already in memory at that point, it just looks at the partition
    table copy in RAM, and tells BIOS where to read from the disk. The MBR
    is not large enough to read using anything but BIOS calls, and the BIOS
    takes its parameters from the partition table, so in that sense, the
    MBR is system and disk geometry-agnostic. It is the data contained
    within the partition table (which is a data structure contained
    *within* the MBR, and that is easy to confuse with the MBR itself
    unless you know the x86 boot process very well) that is hard disk drive
    specific, and *that* data is placed by a partition table editing
    utility.

    It's also trivial to strip out of a hexdump of an MBR and not overwrite
    on disk. This is why "FDISK /MBR" works in pre-NT versions of Windows
    without blowing away the partition table; it just overwrites the code
    section, which is as much as the MBR code needs, up to 446 bytes in
    size. The partition table then takes up the 64 bytes starting at
    offset 446, followed by the BIOS bootable signature section, which is
    two bytes. (Not all versions of the "standard"---that is,
    Microsoft---MBR use all 446 bytes of the alloted code section. That is
    easily determined looking at a disassembly of the MBR, if you know x86
    assembly language.)

    Anyway, I may have a way to work around having to have that MBR
    particular MBR code. I am going to try that. If that doesn't work, I
    am still looking for someone who has a copy of the code in a Dell MBR
    that can kick off the system restoration process. I may even be able
    to regenerate it in assembler using the description of what the MBR
    code does to kick start the recovery process, though I am not *that*
    gifted at x86 assembly.

    I can assure you that calling Dell technical support and asking for a
    copy of the code will utterly confuse them and cost days. :)

    --- Mike
     
    Michael B. Trausch, Oct 28, 2008
    #3
  4. Michael B. Trausch

    Brian K Guest

    Mike,

    I'm with Daddy. I've never had WinXP install a Standard MBR. Except from the
    Recovery Console but that's not related to installing WinXP.

    How are you determining that the Dell code is gone? Do you still see the
    blue Dell band at the Dell splash screen?
     
    Brian K, Oct 28, 2008
    #4
  5. The blue strip that should display with the 2 second delay is no longer
    there. The MBR that is currently on the system is a Microsoft standard
    MBR. I have verified that by checking it manually. In any case, it's
    not a huge deal one way or another; I'm just asking here for what I
    already know I need. :)

    --- Mike
     
    Michael B. Trausch, Oct 28, 2008
    #5
  6. One other thing:

    Using the DVD provided would be a *great* option... *if* the DVD drive
    in the laptop worked. It does not, however, and we're _still_ trying
    to get Dell to deal with that. If they can't deal with a known dead
    drive efficiently, I've no reason to expect them to cough up 446 bytes
    very quickly either. ;-)

    --- Mike
     
    Michael B. Trausch, Oct 28, 2008
    #6
  7. Michael B. Trausch

    Ben Myers Guest

    All the recovery partition does is restore the original version of
    Windows shipped with the computer plus the drivers needed for the
    computer to operate correctly. I, myself, do not believe in recovery
    partitions. Nosiree. Recovery partitions suck. Totally. Give me a
    real Windows install CD or DVD and a set of drivers matching the
    computer's hardware any day. Reinstalling is a little more
    time-consuming than a recovery partition, but 1000% more reliable. Just
    think what sort of creek you would be on if the hard drive died,
    recovery partition along with it. How about simply contacting Dell and
    asking for the "Windows Reinstallation" CD or DVD? They'll nick you a
    few bucks for it, but think of what you paid as an insurance policy
    against hard drive failure.

    There is a nice how-to in the web for creating a Dell diagnostic
    partition. Honestly, it is hardly worth the bother, especially when you
    can download the Dell diagnostics for your model of computer and run
    them from a CD. There are far more comprehensive free diagnostics
    available anyway... Ben Myers
     
    Ben Myers, Oct 28, 2008
    #7
  8. No, sir. You fail to understand what I have written.

    There are several MBR code segments out there. Microsoft has, with
    every operating system I've ever used of theirs, superimposed their MBR
    loader code ontop of whatever was previously there.

    The laptop isn't mine, by the way, so *I* didn't do anything with it.
    What I *do* know is that the MBR contains a Windows XP MBR, and not the
    Dell MBR that was on it.

    The original recovery partition is there, as is the utility partition.
    The DVD drive on the laptop is also dysfunctional, as in, won't accept
    a disk.

    Yes, and the BIOS can boot those on its own, without help from the
    master boot record.
    Useless, since the drive in the laptop doesn't work. Just want the 446
    bytes that are supposed to be at the beginning of the MBR, that's all.
    In any case, I did find another way around it, so it's not a big deal
    at this point.

    Just an off-hand question---how much do _you_ know about the x86 boot
    process? You seem to talk like you know a lot, but you don't seem to
    know the first thing about a partition table, which would be required
    if you were to know about the MBR, which you'd know about in detail if
    you knew about x86/x86-64 IPL in the first place. I'd hazard a guess
    that you don't know much---if any---assembly language, either.

    Anyway, thanks.

    --- Mike
     
    Michael B. Trausch, Oct 28, 2008
    #8
  9. Michael B. Trausch

    Brian K Guest

    Mike, did you get the MBR I sent?
     
    Brian K, Oct 28, 2008
    #9
  10. Michael B. Trausch

    Daddy Guest

    (below>

    What Ben said about recovery partitions, although I might have chosen a
    stronger term than "suck" to describe it.

    Recovery partitions are for the helpless. (This refers both to users and
    tech support reps.) The rest of us make a series of disk images to which
    we can return at any time.

    Daddy
     
    Daddy, Oct 28, 2008
    #10
  11. Hi!

    Would anything here be helpful?

    http://www.goodells.net/dellrestore/

    It's been a long time since I saw this. I dimly remember some
    discussion of the Dell "blue bar" custom MBR in there somewhere...

    (if someone has already suggested this, feel free to ignore
    me...Google Groups is very clearly *not* updating correctly...)

    William
     
    William R. Walsh, Oct 28, 2008
    #11
  12. Michael B. Trausch

    Daddy Guest

    Your point is correct, of course. I believe the OP would know to erase
    the Dell partition first, before merging the empty space into the C: drive.

    In any case, it's a moot point, since the OP is determined to do things
    like Frank Sinatra. ("I did it ...my way.")

    Daddy
     
    Daddy, Oct 28, 2008
    #12
  13. Michael B. Trausch

    S.Lewis Guest


    "Too smart by half."

    Un-scrambling eggs.
     
    S.Lewis, Oct 28, 2008
    #13
  14. Michael B. Trausch

    Daddy Guest

    I've given the OP a hard enough time and for that I apologize.

    I think it's unwise to meddle with disk metadata, and particularly to
    rescue something as useless as Dell's recovery partition. But that's
    just me and I wish the OP well in his efforts.

    Daddy
     
    Daddy, Oct 28, 2008
    #14
  15. Michael B. Trausch

    S.Lewis Guest



    Hey, I'm all for exploring the cratering of an HPA partition, a utility
    partition, the system partition and even the hidden image partition.

    AFTER........I've cloned the drive.

    And in all fairness, I've cratered a few.

    Humility is a wonderful thing.
     
    S.Lewis, Oct 28, 2008
    #15
  16. Jean Rosenfeld, Oct 29, 2008
    #16
  17. Apologies. Just saw that William walsh already gave this link.
     
    Jean Rosenfeld, Oct 29, 2008
    #17
  18. No, I didn't, but thanks.

    I did manage to figure out how to boot the recovery partition
    manually... only to find out that something appears to be missing from
    it (there should be a Boot\ directory and a bunch of stuff there for
    the Vista PIE, but it's missing somehow or another). There is no way
    any assembly code in 466 bytes could manage to restore *that*, so it's
    either hidden somewhere on the disk or it simply has been messed up by
    the laptop owner's poking around on the drive.

    There are other ways to restore from the DVD that came with the system
    without having a functional DVD drive, but my patience is wearing
    thin. Dell's telephone people are a real PITA to deal with and I still
    can't get them to send a replacement DVD drive; neither can the owner.
    The machine is definitely under warranty, so I don't know why they're
    being such pains. Or maybe that's why they are...

    This is why I typically build my own systems. Then again, I also don't
    use Windows. It's amazing that an operating system so popular can't
    even apparently have it's DVD put on a USB key and booted from it.
    Maybe there is a way to do it, but I haven't found it yet; the method I
    have used in the past with Windows XP doesn't work with Vista since
    they've changed the entire way the system is bootstrapped.

    --- Mike
     
    Michael B. Trausch, Oct 29, 2008
    #18
  19. Indeed. I use several different methods for backing up my data
    (filesystem snapshots, rsnapshot to an external drive, and periodic
    backups to burned media). I learned years ago the hard way that it's
    useless to rely on a single system for backing things up.

    It's one of the reasons I have installers for my operating system on
    CD as well as on a USB key. I back up all of that which I cannot
    regenerate, and the rest, I have handy to do so; I can replicate my
    system setup in about two hours time from installation to the end of
    the backup extraction should disaster strike. A little longer than
    that if I have to pull a backup from somewhere other than home
    (presuming that say, my backups here are destroyed in a fire or some
    other catastrophe).

    --- Mike
     
    Michael B. Trausch, Oct 29, 2008
    #19
  20. Gparted is a great partition editor. I do believe you meant GRUB --
    and yes, it's an *excellent* boot manager program. Has to be loaded
    second-stage, though, if you use Vista SP1 and have a computer with any
    built-in TPM hardware. There's software that makes it easy to do, but
    using BCDEdit will let you set up the system that way, as well. It's
    more than I expected Microsoft to do, actually; they had the chance to
    make the boot system for Vista lock everything and anything else out.
    They just made it harder to do, and I can live with that.

    --- Mike
     
    Michael B. Trausch, Oct 29, 2008
    #20
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