[Tfug] MBR problems

[A.Chris Hilton]

Keith-

Dig out one of those old PC Dos disk sets you've got lying around (or a
plain old Win9x rescue floppy). Load up debug and do this:

A:\>DEBUG

- f 200 L200 0

- a 100                

mov ax,301 (ignore the segment:offset values that show up at this point)

mov bx,200

mov cx,1

mov dx,0080 (for first hd, 0081 for second, etc)

int 13

int 3

<ENTER>

- d 100 LF (should produce the following line)

B8 01 03 BB 00 02 B9 01-00 BA 80 00 CD 13 CC (If your hex dump doesn't
look very much like this line, Q and start over)

- g=100

- q

This procedure clears the partition sector of the target drive.  Good
Luck.

-C-

On Fri, 24 Jan 2003 16:45:47 -0700
"Keith Davey" <kjdavey@earthlink.net> wrote:

> Good Day Bowie,
> 
> Thanks for your answer.  I verified that /dev/hda was infact the old
> NT C: drive via fdisk before running the command.   I also figured
> that there might be a problem beyond the first 512 bytes so I issued
> the same dd command this time with a count=5.  That should have put me
> well into the data reagon of the disk.  However it is still a no go. 
> In addition I cleared the original NTFS partition, and created the
> nessesary linux partitions via fdisk. The only other time I have seen
> anything remotely similar to this was with a FreeBSD install that had
> "guessed" the wrong drive geometry.  The install appeared to go off
> without a hitch, but the reboot showed that NO data had actualy been
> written to the disk.  As I know the geometry is correct the only other
> thing I can think of is hardware failure.   Any further opinions or
> suggestions are most welcome!
> 
> Keith Davey
> Storage System Div
> IBM Corp.
> ----- Original Message -----
> From: "Bowie J. Poag" <bpoag@comcast.net>
> To: <tfug@tfug.org>
> Cc: <kdavey@gus33.homeip.net>
> Sent: Friday, January 24, 2003 1:02 PM
> Subject: Re: [Tfug] MBR problems
> 
> 
> >
> > Keith,
> >
> > 1) From your description, it sounds like your MBR has been cleared,
> > but
> the
> > first sector of the first available boot device (not necessarrily
> > the
> first
> > partition) still references NTLDR.  Have a look with Linux fdisk,
> > and
> you'll
> > see which partition is declared bootable. It has a star next to it.
> > This
> one
> > is the culprit. Format it, or do as you've done -- just pave it over
> > with dd. For a more elegant solution, tell lilo to burn info to both
> > first
> sector
> > _and_ MBR.
> >
> > 2) The default boot device may not be /dev/hda. When your system
> > boots and goes thru POST, it determines whether or not the device
> > you've declared in BIOS is bootable. If it isnt, it usually falls
> > over quietly to whatever you've declared as the second  boot device.
> > If you blanketed the suspect drive with dd and it still chokes, you
> > may have unsuspectingly bulldozed
> the
> > wrong drive. :)
> >
> > 3) Bottom line is, you'll need to fully format whatever partition is
> > the
> one
> > now declared as bootable on the drive. Full format, not quick.
> > Problem solved.
> >
> >
> > Cheers,
> > Bowie
> >
> >
> > ----- Original Message -----
> > From: "Leo Przybylski" <leo@leosandbox.org>
> > To: <tfug@tfug.org>
> > Sent: Friday, January 24, 2003 9:00 AM
> > Subject: Re: [Tfug] MBR problems
> >
> >
> > > Keith,
> > >
> > > Looks like you just cleared the MBR, but what if the problem isn't
> > > in the MBR? Was the drive partitioned when NT was installed on it?
> > > Probably all the partition information is lost now that the MBR is
> > > wiped out, but I'd check anyway. If the partition information is
> > > still there, perhaps the MBR wasn't wiped out afterall.
> > >
> > > One last thing you might try. Have you tried low-level format yet?
> > > This should zero out the entire drive. If there was ever a hint of
> > > an NTLDR before, there won't be after low-level format, right?
> > >
> > > -Leo Przybylski
> > > http://foopan.leosandbox.org
> > > http://grow.arizona.edu
> > >
> > > Keith Davey wrote:
> > >
> > > >Hi Gang,
> > > >
> > > >I am trying to convert an ageing win2k box over to linux after
> > > >the
> win2k
> > > >system crashed with NTLDR missing.  However after what apears to
> > > >have
> > been
> > > >a succesfull install of linux, a reboot still gives me nothing
> > > >but:
> > > >
> > > >NTLDR Missing
> > > >
> > > >I tried to correct this by issuing  dd if=/dev/zero of=/dev/hda
> > > >bs=512 count=1
> > > >
> > > >But even after this I still get NTLDR Missing.
> > > >
> > > >Any clues as to how I might clear this error?
> > > >
> > > >Keith Davey
> > > >Storage Systems Div
> > > >IBM Corp