3.0.3rc3 qcow image created with qemu-img not usable?

3.0.3rc3 qcow image created with qemu-img not usable?

[Timo Benk]

Hi,

i am new to the qcow image format, so please forgive me if the following
is just totally stupid:-)

I try to use a qcow formatted image in Xen created by qemu-img.

# qemu-img create -f qcow /tmp/test.img 1G

Then i try to attach that image to Domain-0.

# xm block-attach Domain-0 tap:qcow:/tmp/test.img /dev/xvda1 w 0

No error message so far, but ...

# mount /dev/xvda1 /mnt
mount: special device /dev/xvda1 does not exist

# xm block-list Domain-0
Vdev  BE handle state evt-ch ring-ref BE-path
51714    0    0     3      23     8
  /local/domain/0/backend/tap/0/51714

# xm block-detach Domain-0 /dev/xvda1

# xm block-list Domain-0
Vdev  BE handle state evt-ch ring-ref BE-path
51714    0    0     3      23     8
  /local/domain/0/backend/tap/0/51714

qcow images created with qcow-create are working without any problems.

And a few additional questions i have:

- Is qcow encryption supported?
- is qcow compression supported?

Greetings,
-timo

-- 
Timo Benk - Jabber ID: fry@jabber.org - ICQ ID: #241877854
PGP Public Key: http://m28s01.vlinux.de/timo_benk_gpg_key.asc

Re: 3.0.3rc3 qcow image created with qemu-img not usable?

[Anthony Liguori]

You cannot attach block devices to Domain-0.  Furthermore, you cannot 
attach non-raw file-based block devices to paravirtual domains.

Regards,

Anthony Liugoir

Timo Benk wrote:
> Hi,
> 
> i am new to the qcow image format, so please forgive me if the following
> is just totally stupid:-)
> 
> I try to use a qcow formatted image in Xen created by qemu-img.
> 
> # qemu-img create -f qcow /tmp/test.img 1G
> 
> Then i try to attach that image to Domain-0.
> 
> # xm block-attach Domain-0 tap:qcow:/tmp/test.img /dev/xvda1 w 0
> 
> No error message so far, but ...
> 
> # mount /dev/xvda1 /mnt
> mount: special device /dev/xvda1 does not exist
> 
> # xm block-list Domain-0
> Vdev  BE handle state evt-ch ring-ref BE-path
> 51714    0    0     3      23     8
>   /local/domain/0/backend/tap/0/51714
> 
> # xm block-detach Domain-0 /dev/xvda1
> 
> # xm block-list Domain-0
> Vdev  BE handle state evt-ch ring-ref BE-path
> 51714    0    0     3      23     8
>   /local/domain/0/backend/tap/0/51714
> 
> qcow images created with qcow-create are working without any problems.
> 
> And a few additional questions i have:
> 
> - Is qcow encryption supported?
> - is qcow compression supported?
> 
> Greetings,
> -timo
> 

Re: Re: 3.0.3rc3 qcow image created with qemu-img not usable?

[Timo Benk]

Anthony Liguori wrote:
> You cannot attach block devices to Domain-0.  Furthermore, you cannot
> attach non-raw file-based block devices to paravirtual domains.
I can and Xen can do so too :-)

I just followed the description in [1].

And the point is as i have explained: it works with qcow-create created
images but not with qemu-img created images.

I do not know if that is by design or a bug.

IMHO the Xen qcow format is compatible with qemu so it should work.

[1]http://xenbits.xensource.com/xen-3.0.3-testing.hg/tools/blktap/README

Greetings,
-timo
-- 
Timo Benk - Jabber ID: fry@jabber.org - ICQ ID: #241877854
PGP Public Key: http://m28s01.vlinux.de/timo_benk_gpg_key.asc

Re: Re: 3.0.3rc3 qcow image created with qemu-img not usable?

[Anthony Liguori]

Timo Benk wrote:
> Anthony Liguori wrote:
>   
>> You cannot attach block devices to Domain-0.  Furthermore, you cannot
>> attach non-raw file-based block devices to paravirtual domains.
>>     
> I can and Xen can do so too :-)
>   

Sorry, I forgot about blktap...

blktap requires a certain cluster size for qcow images IIRC.  That's 
probably why qemu-img doesn't work.

Regards,

Anthony Liguori

> I just followed the description in [1].
>
> And the point is as i have explained: it works with qcow-create created
> images but not with qemu-img created images.
>
> I do not know if that is by design or a bug.
>
> IMHO the Xen qcow format is compatible with qemu so it should work.
>
> [1]http://xenbits.xensource.com/xen-3.0.3-testing.hg/tools/blktap/README
>
> Greetings,
> -timo
>