[Qemu-devel] booting from /dev/hd?

[Qemu-devel] booting from /dev/hd?

[Tim]

Hello,

I know it is considered dangerous, but I am willing to accept the
risk...  Has anyone been able to boot a virtual machine from their main
boot drive while the drive is in use?

More specifically, I have a dual boot system, win2k/debian, and I would
like to try booting windoze from this disk as a guest OS while running
the linux system from this same disk.  In order to protect my disk from
erroneous writes, I planned on running the vm system with -snapshot.

I have tried this, and with basic options:

qemu -hda /dev/hda -snapshot -boot c

my bootloader (grub) comes up just fine, but once I select win2k, it
reports a disk read error.  When booting Debian, it loads the kernel and
tries to begin booting, but just hangs.  This may be because my kernel
is customized for my Athlon though...  
I figured the windoze issue might be a geometry problem, so I ran 
`fdisk -l /dev/hda' and then used that geometry:

qemu -hda /dev/hda -snapshot -boot c -hdachs 4865,255,63

and I get the same results.  Perhaps I need to use a non-LBA geometry or
something?  I really don't know much about disk geometry, just a
guess...


Has anyone tried doing something similar to what I am attempting?  If
so, did you have any success, and what did you try that I haven't?  I am
pretty sure I have permissions right in the host OS, is there anything I
am forgetting?

thanks,
tim

Re: [Qemu-devel] booting from /dev/hd?

[Antony T Curtis]

On Mon, 2004-05-31 at 18:10, Tim wrote:
> Hello,
> 
> I know it is considered dangerous, but I am willing to accept the
> risk...  Has anyone been able to boot a virtual machine from their main
> boot drive while the drive is in use?

Yes, but I made a COW image from the hard drive so I don't trash the
hard drive for real.

> More specifically, I have a dual boot system, win2k/debian, and I would
> like to try booting windoze from this disk as a guest OS while running
> the linux system from this same disk.  In order to protect my disk from
> erroneous writes, I planned on running the vm system with -snapshot.
> 
> I have tried this, and with basic options:
> 
> qemu -hda /dev/hda -snapshot -boot c
> 
> my bootloader (grub) comes up just fine, but once I select win2k, it
> reports a disk read error.  When booting Debian, it loads the kernel and
> tries to begin booting, but just hangs.  This may be because my kernel
> is customized for my Athlon though...  
> I figured the windoze issue might be a geometry problem, so I ran 
> `fdisk -l /dev/hda' and then used that geometry:
> 
> qemu -hda /dev/hda -snapshot -boot c -hdachs 4865,255,63
> 
> and I get the same results.  Perhaps I need to use a non-LBA geometry or
> something?  I really don't know much about disk geometry, just a
> guess...

Try to do it with LBA Compat geometry.... -hdachs 77536,16,63 in your
case...

> 
> Has anyone tried doing something similar to what I am attempting?  If
> so, did you have any success, and what did you try that I haven't?  I am
> pretty sure I have permissions right in the host OS, is there anything I
> am forgetting?
> 
> thanks,
> tim
> 
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
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-- 
Antony T Curtis <antony.t.curtis@ntlworld.com>

Re: [Qemu-devel] booting from /dev/hd?

[Tim]

> Yes, but I made a COW image from the hard drive so I don't trash the
> hard drive for real.

It's good to hear someone else has been doing this.  I just created one
as you say:

qemu-mkcow -f /dev/hda hda.img


> Try to do it with LBA Compat geometry.... -hdachs 77536,16,63 in your
> case...

Just tried booting with this, both with -snapshot and the COW image.
Still no worky.  I am using the latest qemu CVS.  Which version have you
made it work with?  Which win version?

thanks for all your help,
tim

Re: [Qemu-devel] booting from /dev/hd?

[Grzegorz Kulewski]

I tried it with VMWare some time ago. Host was WinXP and guest was Linux 
2.4 and 2.6. Both OSes were on (different) partitions on the same disc. It 
worked ok and I had never any dataloss. But no guarantee of course :-).

I do not know if it will work with QEMU.

But feel free to tell me about your results.


Grzegorz Kulewski