[Qemu-devel] disk images & driver geometry

[Qemu-devel] disk images & driver geometry

[Christopher Friedt]

Hi everyone,

has there been any work done in the last few months towards hard disk 
geometry, so that partition tables / mbr's in raw hard disk files can be 
stored for later use?

That's something that would be tremendously useful with the -hda option, 
so that one could use a file for a virtual disk and expect qemu to 
recognize the partition information from it. Usually if one does a 
typical install with a linux distro, the linux install will format the 
main hard disk to have 3 partitions (boot,root,swap), but if it's just a 
file then that partition / mbr info isn't really recognized by qemu.

I've been out of the loop w/ what's happening on the bleeding edge with 
qemu for a few months, so I thought I'd just ask here.

~/Chris

Re: [Qemu-devel] disk images & driver geometry

[Anthony Liguori]

Christopher Friedt wrote:
> Hi everyone,
>
> has there been any work done in the last few months towards hard disk 
> geometry, so that partition tables / mbr's in raw hard disk files can 
> be stored for later use?
>
> That's something that would be tremendously useful with the -hda 
> option, so that one could use a file for a virtual disk and expect 
> qemu to recognize the partition information from it. Usually if one 
> does a typical install with a linux distro, the linux install will 
> format the main hard disk to have 3 partitions (boot,root,swap), but 
> if it's just a file then that partition / mbr info isn't really 
> recognized by qemu.

I have no idea what you're talking about.  QEMU doesn't care whether you 
use a physical disk or a file.  It handles geometry the same way.

Is there a concrete example that doesn't work that you think should?

Regards,

Anthony Liguori

> I've been out of the loop w/ what's happening on the bleeding edge 
> with qemu for a few months, so I thought I'd just ask here.
>
> ~/Chris
>
>
>

Re: [Qemu-devel] disk images & driver geometry

[Christopher Friedt]

Anthony Liguori wrote:
> I have no idea what you're talking about.  QEMU doesn't care whether you 
> use a physical disk or a file.  It handles geometry the same way.
> 
> Is there a concrete example that doesn't work that you think should?

Yes, a simple example is running CentOS after a typical install from a 
hard disk image.

If Qemu is started with the installation cdrom (-cdrom CentOS-1of4*.iso) 
the installation creates several partitions on the virtual disk, 
including /boot, and a logical disk containing /. The first 512 Bytes of 
the disk image are assumed to be the MBR of the disk, which is where the 
installation will write the boot loader.

After installation, qemu is started with

qemu -hda centos.img -boot c

and it hangs after saying 'booting from hard disk'

If anyone knows a way to work around this, please don't hesitate to 
offer a suggestion.

~/Chris

Re: [Qemu-devel] disk images & driver geometry

[Daniel P. Berrange]

On Fri, Aug 31, 2007 at 03:09:19PM -0400, Christopher Friedt wrote:
> Anthony Liguori wrote:
> >I have no idea what you're talking about.  QEMU doesn't care whether you 
> >use a physical disk or a file.  It handles geometry the same way.
> >
> >Is there a concrete example that doesn't work that you think should?
> 
> Yes, a simple example is running CentOS after a typical install from a 
> hard disk image.
> 
> If Qemu is started with the installation cdrom (-cdrom CentOS-1of4*.iso) 
> the installation creates several partitions on the virtual disk, 
> including /boot, and a logical disk containing /. The first 512 Bytes of 
> the disk image are assumed to be the MBR of the disk, which is where the 
> installation will write the boot loader.
> 
> After installation, qemu is started with
> 
> qemu -hda centos.img -boot c

That scenario works just fine for me when I try it with either  RHEL-5
or Fedora Core 6 / 7. QEMU reads the MBR from the disk I pass with -hda, 
whether that's backed by a physical device, or a file backed disk & will
succesfully boot the OS.  I just followed the recommended partitioning
scheme that RHEL-5 installer suggests making no changes.

Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
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Re: [Qemu-devel] disk images & driver geometry

[Anthony Liguori]

On Fri, 2007-08-31 at 15:09 -0400, Christopher Friedt wrote:
> Anthony Liguori wrote:
> > I have no idea what you're talking about.  QEMU doesn't care whether you 
> > use a physical disk or a file.  It handles geometry the same way.
> > 
> > Is there a concrete example that doesn't work that you think should?
> 
> Yes, a simple example is running CentOS after a typical install from a 
> hard disk image.
> 
> If Qemu is started with the installation cdrom (-cdrom CentOS-1of4*.iso) 
> the installation creates several partitions on the virtual disk, 
> including /boot, and a logical disk containing /. The first 512 Bytes of 
> the disk image are assumed to be the MBR of the disk, which is where the 
> installation will write the boot loader.
> 
> After installation, qemu is started with
> 
> qemu -hda centos.img -boot c
> 
> and it hangs after saying 'booting from hard disk'

QEMU does the Right Thing in this case.  If you're having trouble
booting, it's not because of disk geometry.

Please post a link to the exact location of your install disk, the
command you used to create the disk, the command lines you're using to
install and launch, and the version of QEMU.

Regards,

Anthony Liguori

> If anyone knows a way to work around this, please don't hesitate to 
> offer a suggestion.
> 
> ~/Chris
> 
> 

Re: [Qemu-devel] disk images & driver geometry

[Christopher Friedt]

sorry, that subject should have read 'drive geometry'

Christopher Friedt wrote:
> Hi everyone,
> 
> has there been any work done in the last few months towards hard disk 
> geometry, so that partition tables / mbr's in raw hard disk files can be 
> stored for later use?
> 
> That's something that would be tremendously useful with the -hda option, 
> so that one could use a file for a virtual disk and expect qemu to 
> recognize the partition information from it. Usually if one does a 
> typical install with a linux distro, the linux install will format the 
> main hard disk to have 3 partitions (boot,root,swap), but if it's just a 
> file then that partition / mbr info isn't really recognized by qemu.
> 
> I've been out of the loop w/ what's happening on the bleeding edge with 
> qemu for a few months, so I thought I'd just ask here.
> 
> ~/Chris
> 
> 
> 
>