News Group Posts

File System Larger than Physical

Disk

From: Bela Lubkin <belal@sco.com>
Subject: Re: SCO HD Crash - Pls Help!
Date: Fri, 24 Oct 2003 02:30:20 GMT
References: <newscache$ifd7nh$0j3$1@catflap.electro-clash.com> 

Steve Netting wrote:

> I have a SCO box (OpenServer 5.0.5), which is randomly crashing.    When
> rebooting, fsck runs and reports a number of problems, mainly "File System
> larger than Physical Disk - please backup and rebuild".

That message indicates a very serious problem, very likely the cause of
_all_ the system's problems.

As far as I know, there are only two ways to get a filesystem larger
than the device.  One is to run `mkfs -y /dev/some-device 123456`,
giving too large a number.  The "-y" overrides mkfs's normal caution
about the requested size not matching the size of the device.  The other
way is to make an image backup of a filesystem, then restore it onto a
smaller device.

> It seems that the cpio backups have been failing for the last x months (but
> not reporting an error - they just 'hang' - probably due to FS corruption!).
> 
> So, I have a SCO box, with no backups (cpio hanging) - and a disk full of
> major FS errors.    The machine however is up and running (albeit crashing
> every few hours).    We really need to rescue as much data as possible.
> 
> How should I attack this?     Is there any trick to fixing / recovering from
> this sort of state?

Boot from a crash recovery floppy set.  Mount the hard disk filesystem
read-only.  Attempt to back it up.

You say "cpio hanging".  A cpio backup is typically done with a pipeline
where one part collects the filenames:

  find . -print

and the other part backs them up:

                | cpio -o -O /dev/rStp0

You can do these separately, to get a better idea of where it's hanging.
Suppose you had booted from a boot/root set; /mnt was mounted from the
hard disk; and /mnt2 was another hard disk you added to the machine as a
writable scratch area.  You could do something like:

  cd /mnt
  (find . -print  > /mnt2/file-list; echo DONE) &
  cd /mnt2
  ls -l file-list
  [wait a while]
  ls -l file-list

Eventually you'll see "DONE".  Or maybe hard disk activity will stop and
/mnt2/file-list will stop growing.  If the list completes, you can back
up from it, e.g.;

  cd /mnt
  cpio -ov -O /dev/rStp0 < /mnt2/file-list

If this hangs, you'll be able to tell because the tape will stop
spinning and the filenames will stop scrolling.  At that point you'll
have a tape containing _some_ of the files you want to back up.  You can
restore it on another system.  Meanwhile, you reboot, edit
/mnt2/file-list to remove the files already backed up, and back up again
to another tape.  Repeat until frustrated.

You may find that the tape contains less files than you saw printed on
the screen.  The hang may cause the tape to stop writing before it
should.  When cutting down the list, be sure to remove only files that
have already been successfully restored elsewhere (plus the file(s) that
cause the hangs).

> I would try installing a second disk, creating identical sized partitions -
> and manually moving data accross.  However, I have no idea how to re-create
> the boot blocks etc.

This would also work -- in fact copying directly across will probably be
a lot easier than doing it with tapes.  You can use any archiver; tar
and cpio come with the system, the various "supertar" products are
better.

The best approach here would probably be to put in a new drive (take out
the old), do a fresh install, then add the old drive as a secondary
drive, copy the data files over.

You're either going to learn a lot about the system very fast, or you'll
end up hiring a consultant...

>Bela<

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