Libguestfs - Nov 2013 - Re: Problem using virt-sysprep with RBD images

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.  Perhaps "safe_strdup"?  I'm not sure
where
"safe_strdup" is to confirm, but it looks like other functions use the
"safe_stardup" function.

With that in mind, I didn't want to have to reinvent create_drive_non_file,
and without a better understanding of how all the code works together, I
came up with a little hack which basically prepends the slash if there
isn't one.

  if (exportname[0] != '/') {
//    char name[(sizeof exportname) + 1];
    char name[256];
    snprintf(name, sizeof name, "/%s", exportname);
    exportname = name;
  }

My concern is long rbd-pool/rbd names, hence the commented out line, but
that causes the name of the disk to be:
>> qemu-system-x86_64: -drive
file=rbd:libvirt: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:
could not open disk image
rbd:libvirt:mon_host=192.168.0.40\:6789\;192.168.0.35\:6789\;192.168.0.2\:6789:auth_supported=none:
Invalid argument

For some reason, the commented out line in the if statement above is
truncating the end of the name.  Admittedly, my C skills are a bit rusty,
so I'm probably overlooking something obvious.

Any thoughts on this approach?

Thanks,
Jon A


On Wed, Nov 6, 2013 at 12:22 PM, Richard W.M. Jones
<rjones@redhat.com>wrote:
> On Wed, Nov 06, 2013 at 11:17:14AM -0700, Jon wrote:
> > I tried to comment this out and recompile guestfs, but I get an error:
> >
> > make[2]: Entering directory `/root/libguestfs-1.25.6/builder'
> > ocamlfind ocamlopt -g -warn-error CDEFLMPSUVYZX -package str,unix -I
> > ../src/.libs -I ../ocaml -I ../mllib -package gettext-stub -c
builder.ml-o
> > builder.cmx
> > File "builder.ml", line 53, characters 4-14:
> > Error: Unbound value List.iteri
> > make[2]: *** [builder.cmx] Error 2
> > make[2]: Leaving directory `/root/libguestfs-1.25.6/builder'
> > make[1]: *** [all-recursive] Error 1
> > make[1]: Leaving directory `/root/libguestfs-1.25.6'
> > make: *** [all] Error 2
>
> Hmm, this is actually another bug :-(  The attached patch should fix
> this one and allow you to compile libguestfs with the older version of
> OCaml that didn't have List.iteri.
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> virt-top is 'top' for virtual machines.  Tiny program with many
> powerful monitoring features, net stats, disk stats, logging, etc.
> http://people.redhat.com/~rjones/virt-top
>

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
Fedora now supports 80 OCaml packages (the OPEN alternative to F#)

On Wed, Nov 06, 2013 at 09:37:01PM +0000, Richard W.M. Jones
wrote:
> 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.
(I mean, a URL that has a path that doesn't start with a "/".)

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
Fedora now supports 80 OCaml packages (the OPEN alternative to F#)

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
> Fedora now supports 80 OCaml packages (the OPEN alternative to F#)
>