Misalf,
thanks for suggestion, I will try to add nodhcp to cmdline.txt (never managed to build initrd).
From the other hand, for configuration I do need dhcp since I have do download some things from repositories. Static IP is made when all the software is ready.
Editing bootsync.sh is easier than cmline.txt... Is there any way to enable dhcp in bootsync.sh if I need it?