reconstructing dparam disk geometry changed

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From: Bela Lubkin <belal@caldera.com>
Subject: Re: OSR 5.0.6a Strange problem after BIOS upgrade FLASH and IDE
Date: Wed, 16 Jan 2002 23:05:26 GMT
References: <20020113144645.I14415@mammoth.ca.caldera.com> <Pine.SC5.4.43.0201161231040.3858-100000@xenau105.zenez.com> 

Boyd Lynn Gerber wrote:

> On Sun, 13 Jan 2002, Bela Lubkin wrote:
> > Since you have a new blank-slate Unix install on the 80GB drive, and
> > have the 40GB drive in place, you're most of the way there.  You need to
> > do something like:
> >
> >   strings -a /dev/rhd20 | grep cyls= > /tmp/old-parms
> 
> I found 9693 128 63 as the correct parameters.
> 
> >   dparam /dev/rhd10                         # print existing parms
> >   dparam /dev/rhd10 cyls hds ... cyls secs
> 
> dparam /dev/rhd20 9693 128 0 0 0 8 19157 63 and setting the bios to auto
> was the solution.
> 
> I have found through a bit of testing that after a HD has been installed
> and working to not run the BIOS HD detect when adding a new HD.  It is
> better to manually set it up with the proper HD settings.
> 
> Thanks to every one.  I was finally able to recover my friends data.

You seem to think that the most important thing learned here is "don't
run BIOS HD detect after the HD is already working with OpenServer".  I
say you've learned something far more important (which ought to be
written up for the FAQ).

That is: if you _do_ run the BIOS HD detect, and lose control of the
drive, you can recover it.

First, learn the "right" parameters according to Unix.  You might have
previously recorded them, might be able to `strings` the drive, might be
able to examine /usr/adm/messages or /usr/adm/syslog from a prior backup
of the drive.  Or you might, in fact, be able to use one of the BIOS's
parameter sets (does 9693/128/63 match any of the configs the BIOS came
up with?)  -- that is, it may be the case that even with the BIOS
claiming the same parameters as it always did, you still need to have
Unix restamp the drive.

Second, restamp the drive.  That means getting the Unix kernel up and
running, could be from a boot floppy, the install CD with "tools", a 3rd
party crash recovery floppy (RecoverEDGE, AirBag, etc.), or by putting
in a different hard disk and doing a minimal install.  Get to a shell
prompt.  Find or create a device node that points to the drive in
question (/dev/rhd00 if it's primary/master; could be rhd10 or something
else).  Run:

  dparam -w /dev/rhd00
  dparam    /dev/rhd00
            # or rhd10 or whatever

to print existing parameters, then run:

  dparam    /dev/rhd00 cyls hds ppp qqq rrr sss cyls secs
            # or rhd10 or whatever

where ppp/qqq/rrr/sss are the middle 4 of the existing parameters, and
cyls/hds/secs are the "right" parameters.  "cyls" gets stamped twice,
once for the size of the drive and once for landing zone.

Third, go into BIOS setup and set the drive back to "auto".

Fourth, if necessary, rearrange drives (e.g. if this was once, and is
desired again to be the boot drive, move it back to primary/master).

This won't necessarily work in all cases, it's just _one_ discovered way
of recovering from an IDE disk geometry problem.  Also, steps "Second"
and "Third" might need to be done in the reverse order, and you will
probably have to change things again in the BIOS if you physically
rearrange drives.

>Bela<
 

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