Converting QEMU Harddisk to native Partition

Converting QEMU Harddisk to native Partition

[Erik Rull]

Hi all,

I have currently virtualized two partitions (/dev/sda2 and /dev/sda3) that 
are exposed as QEMU Harddisks to the Windows XP Guest (Drive C and D there).
Are there possibilities to convert or adapt those to native partitions or 
native disks so that I could theoretically boot the Windows that is placed 
in the virtual disk natively?

Thanks!

Best regards,

Erik

Re: Converting QEMU Harddisk to native Partition

[David Mair]

On 02/15/2011 10:06 AM, Erik Rull wrote:
> Hi all,
>
> I have currently virtualized two partitions (/dev/sda2 and /dev/sda3)
> that are exposed as QEMU Harddisks to the Windows XP Guest (Drive C and
> D there).
> Are there possibilities to convert or adapt those to native partitions
> or native disks so that I could theoretically boot the Windows that is
> placed in the virtual disk natively?
>
> Thanks!

Anything that works on real hardware is likely to work if run in a 
guest. At the very least, one of several similar and equivalent methods 
would be, create another virtual disk a bit bigger than the Windows 
partition you want to make native and attach it to a VM with the Windows 
partition you want to make native and boot a linux rescue disk. Put a 
linux file system on the new disk and mount it (say at /mnt/workspace) 
then, assuming the Windows partition you want to make native is hda1:

# dd if=/dev/sda2 of=/mnt/workspace/windowsCdrive.img bs=1M
# dd if=/dev/sda3 of=/mnt/workspace/windowsDdrive.img bs=1M
# scp /mnt/workspace/windows*img user@vmhost:~/

I'm assuming you get how that would give you a block copy of the guest 
partitions as files on the host, which you could then lay down on a real 
disk via dd and a USB device for example.

-- 
David.

Re: Converting QEMU Harddisk to native Partition

[Erik Rull]

David Mair wrote:
>
>> I have currently virtualized two partitions (/dev/sda2 and /dev/sda3)
>> that are exposed as QEMU Harddisks to the Windows XP Guest (Drive C and
>> D there).
>> Are there possibilities to convert or adapt those to native partitions
>> or native disks so that I could theoretically boot the Windows that is
>> placed in the virtual disk natively?
>>
> Anything that works on real hardware is likely to work if run in a
> guest. At the very least, one of several similar and equivalent methods
> would be, create another virtual disk a bit bigger than the Windows
> partition you want to make native and attach it to a VM with the Windows
> partition you want to make native and boot a linux rescue disk. Put a
> linux file system on the new disk and mount it (say at /mnt/workspace)
> then, assuming the Windows partition you want to make native is hda1:
>
> # dd if=/dev/sda2 of=/mnt/workspace/windowsCdrive.img bs=1M
> # dd if=/dev/sda3 of=/mnt/workspace/windowsDdrive.img bs=1M
> # scp /mnt/workspace/windows*img user@vmhost:~/
>
> I'm assuming you get how that would give you a block copy of the guest
> partitions as files on the host, which you could then lay down on a real
> disk via dd and a USB device for example.
>

Yeah, I thought about a similar approach already but it looked too complex 
to me :-) I assume that my hardware resources might be too limited for such 
an operation, but I will give it a try. For saving space I could try to do 
a .gz or .tgz out of it right (using "dd | tar...")?
Are there other possibilities from the host side to handle that? I heard 
about the qemu-img tool but it doesn't seem to match my usecase.
Or have I just missed some parameters?

Thanks.

Best regards,

Erik

Re: Converting QEMU Harddisk to native Partition

[David Mair]

On 02/15/2011 01:54 PM, Erik Rull wrote:
> David Mair wrote:
>>
>>> I have currently virtualized two partitions (/dev/sda2 and /dev/sda3)
>>> that are exposed as QEMU Harddisks to the Windows XP Guest (Drive C and
>>> D there).
>>> Are there possibilities to convert or adapt those to native partitions
>>> or native disks so that I could theoretically boot the Windows that is
>>> placed in the virtual disk natively?
>>>
>> Anything that works on real hardware is likely to work if run in a
>> guest. At the very least, one of several similar and equivalent methods
>> would be, create another virtual disk a bit bigger than the Windows
>> partition you want to make native and attach it to a VM with the Windows
>> partition you want to make native and boot a linux rescue disk. Put a
>> linux file system on the new disk and mount it (say at /mnt/workspace)
>> then, assuming the Windows partition you want to make native is hda1:
>>
>> # dd if=/dev/sda2 of=/mnt/workspace/windowsCdrive.img bs=1M
>> # dd if=/dev/sda3 of=/mnt/workspace/windowsDdrive.img bs=1M
>> # scp /mnt/workspace/windows*img user@vmhost:~/
>>
>> I'm assuming you get how that would give you a block copy of the guest
>> partitions as files on the host, which you could then lay down on a real
>> disk via dd and a USB device for example.
>>
>
> Yeah, I thought about a similar approach already but it looked too
> complex to me :-) I assume that my hardware resources might be too
> limited for such an operation, but I will give it a try. For saving
> space I could try to do a .gz or .tgz out of it right (using "dd |
> tar...")?
> Are there other possibilities from the host side to handle that? I heard
> about the qemu-img tool but it doesn't seem to match my usecase.
> Or have I just missed some parameters?

qemu-nbd (see man qemu-nbd) might be what you are looking for, booting 
a guest with it attached seems simpler to me so I admit I haven't tried 
qemu-nbd.

If it's a simple block image you can mount it on the host via the loop 
device like any unencoded disk image in a file.

You could go directly to a USB disk in a guest just by using USB 
pass-thru of a physical disk, I'd boot a linux rescue disk and use dd.

-- 
David Mair.