[Libguestfs] virt-resize problem for Windows 2003

[Xinglong Wu]

Thanks for the reply! And sorry that I'm unable to provide such a patch at
this stage, but filed the bug report. Hopefully the bug can fixed in the
near future.

Xinglong


On Wed, Nov 6, 2013 at 8:00 PM, Richard W.M. Jones <rjones at redhat.com>wrote:

> On Wed, Nov 06, 2013 at 10:58:06AM +0800, Xinglong Wu wrote:
> > Hi,
> >
> >      I'm using virt-resize to expand the primary partition (C:) in a
> > Windows 2003 image. The command works fine but after expanding, when I
> boot
> > into Windows 2003, all the other partitions (D:, E:, and F:) are lost.
>
> I can see why this would happen.
>
> In the Windows registry, Windows stores drive letter mappings using a
> (basically crazy) system using the partition offset.  It is described here:
>
>   http://www.goodells.net/multiboot/partsigs.shtml
>   "How does Windows XP remember drive letters?"
>
> We implement this in libguestfs:
>
>
> https://github.com/libguestfs/libguestfs/blob/aee6fc4863c170d08e572dbdcfcb6f328edfc013/src/inspect-fs-windows.c#L545
>
> Virt-resize moves partitions around, so of course the partition offset
> changes and we don't update the registry to reflect this.  As a result
> Windows cannot find the D:/E:/... partitions any longer.  (I believe
> the C: drive probably works a bit differently, so the C: drive isn't
> "lost").
>
> Anyway, we could conceivably fix up the Registry in virt-resize.  You
> would need to file an RFE bug:
>
>   http://libguestfs.org/guestfs-faq.1.html#how-do-i-propose-a-feature
>
> Patches would be even better, since I don't know when we'd get around
> to fixing such a complex corner-case.
>
> > After using the disk management tool within Windows 2003, I can re-label
> > the above three partitions and all the files are still there. But it is
> > really annoying because every time you have to do some work by hand after
> > expanding the disk size. As below is the details:
> >
> > Host OS: RHEL6.3
> > libguestfs: libguestfs-1.16.19-1.el6.x86_64
> >                  libguestfs-tools-c-1.16.19-1.el6.x86_64
> >                  libguestfs-winsupport-1.0-7.el6.x86_64
>
> It won't fix your problem, but there is a newer version of libguestfs
> available for RHEL 6 users:
>
> https://www.redhat.com/archives/libguestfs/2013-May/msg00100.html
>
> > Guest OS partitions:
> >            C:    /dev/sda1  primary
> >            D:    /dev/sda5  logical
> >            E:    /dev/sda6  logical
> >            F:    /dev/sda7  logical
> >
> > Also, if I use virt-resize on logical partitions (i.e., D: E: or F:), the
> > command runs fine but logical partitions don't actually expand. Exactly
> the
> > same problem as descripted above shows up, and now, these logical
> > partitions don't even change their sizes. Any suggestions?
>
> Virt-resize cannot resize individual logical partitions.  It can only
> resize the extended partition that contains the logical partitions.  See:
>
> http://libguestfs.org/virt-resize.1.html#logical-partitions
>
> This is not expected to change any time soon.
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> virt-p2v converts physical machines to virtual machines.  Boot with a
> live CD or over the network (PXE) and turn machines into KVM guests.
> http://libguestfs.org/virt-v2v
>
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