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Re: [Libguestfs] [libguestfs] Problem using virt-sysprep with RBD images



Hello Rich,

Interesting.  Thanks for the explanation.

When you specify an rbd on the command line for virt-sysprep, do you expect the path to include the monitor address?

e.g.:
>> virt-sysprep -a rbd://host-name/pool-name/device-name

If I understand correctly, libvirt is able to understand the ceph configuration, so when I create a device with qemu-img I only specify the protocol and pool/device.

e.g.:
>> qemu-img create rbd:pool-name/device-name 5G

(there is some voodoo that I don't understand, I've got a whole thread on trying to get qemu-img to create format 2 rbds by default... but that's for another thread)

Would it be possible to specify rbds like this instead?  Or is the scope bigger than I'm understanding and that would cause issues with other disk types specified for the --add parameter.  It seems like --add can take either a URI or a physical disk path.

Thanks for all your help helping me to understand.

Best Regards,
Jon A


On Wed, Nov 6, 2013 at 2:37 PM, Richard W.M. Jones <rjones redhat com> wrote:
On Wed, Nov 06, 2013 at 02:25:54PM -0700, Jon wrote:
> Hello Richard,
>
> Haha, ok, here's a good one: I commented that if statement out at line 300,
> applied your patch (I see you updated the github of this code, perhaps
> that's the best place to grab the code from), and when I run virt-sysprep,
> I get the following parameter for my disk drive:
>
> >> qemu-system-x86_64: -drive
> file=rbd:ibvirt-pool/server-clone-test:mon_host=192.168.0.40\:6789\;192.168.0.35\:6789\;192.168.0.2\:6789:auth_supported=none,cache=writeback,id=hd0,if=none:
> error opening pool ibvirt-pool
>
> Since "ibvirt-pool" doesn't exist. :)
>
> So this says to me that the function "create_drive_non_file" is consuming
> that first slash somewhere.

Unfortunately this code is rather intricate (and intricately broken),
but the problem is likely to be here:

 src/drives.c:
    /* Skip the mandatory leading '/' character on exportname. */
    return safe_asprintf (g, "rbd:%s:mon_host=%s%s%s%s",
                          &src->u.exportname[1],
                          mon_host,
                          username ? username : "",
                          auth,
                          secret ? secret : "");

The problem that this code is trying (and failing) to deal with is
that when you use the URL on the guestfish command line, the URL is
something like "rbd://example.com/foo/bar" and the path part of this
has to start with a "/" character.  There is simply no way to specify
a URL without this.

However this assumption should *not* have made its way into the
libguestfs library, since other paths into this code, such as from
libvirt XML, have no such restrictions.

So it's currently somewhat broken.

Rich.

--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
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