[Libguestfs] Virt-v2v conversion issue

VONDRA Alain AVONDRA at unicef.fr
Tue Oct 14 15:40:22 UTC 2014

I've followed your instructions to trace, but I am not very skilful with gdb, maybe I made a mistake :

(1) As root do:

  echo core.%p > /proc/sys/kernel/core_pattern  -> OK

(2) Before running virt-v2v, do:

  ulimited -c unlimited                 -> I think it's ulimit -c unlimited     -> -> OK

and you should get a core.* file in the current directory when qemu-img segfaults.  Attach that file to gdb to get a stack trace:

  gdb /usr/bin/qemu-img core.XYZ                -> Do I need to wait the crash becase I don't have any core ???
  (gdb) t a a bt


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-----Message d'origine-----
De : Richard W.M. Jones [mailto:rjones at redhat.com]
Envoyé : mardi 14 octobre 2014 16:52
À : VONDRA Alain
Cc : libguestfs at redhat.com
Objet : Re: [Libguestfs] Virt-v2v conversion issue

On Tue, Oct 14, 2014 at 02:43:31PM +0000, VONDRA Alain wrote:
> Rich,
> The conversion did'nt finish, and I don't have any core dump.
> The qemu-img seems to hang, but doesn't crash...

Please connect gdb to the hung process and get a stack trace to find out where it's hanging.

'strace -p ...' output might also be enlightening, if it is not hung but doing "something" (albeit not making progress).

I should also note that if qemu-img convert hits a lot of zeroes in the source (possible, because fstrim wasnt successful), then it will consume CPU skipping them, but won't write anything for a while.


Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines.  Supports shell scripting, bindings from many languages.  http://libguestfs.org

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