[PROBLEM] Resize partition after xbian installation

[namtih]

As Xbian resizes the partition with the first start my last idea is to check the available code at github. The needed part seems to be in the initramfs-package:
https://github.com/xbianonpi/xbian-package-initramfs/blob/master/content/etc/xbian-initramfs/cnvres-code.sh

Much code, but perhaps you will find what you are looking for or at least you will get an idea of the process.
Good luck.