[PROBLEM] Resize partition after xbian installation

[Pascal]

I gave a try to xbian-config, but got this message :

Terminal

This part of code is currently (as of beta1) │
│ obsolete and is disabled. Resize is automatically │
│ provided by initramfs helpers. On this place we │
│ plan to provide easy, simple but fully universal │
│ partition manipulator / copy / resizer to cover │
│ needs of a RPI user.

I have a full backup image made with dd.
I can test everything, I'm able to restore the original,
but not able to extend the mmcblk0p2 partition.