Hello Igor,
thanx for fast reply !
Sorry about this, but I used the file /etc/network/interfaces just as an example.
This was not about setting network settinges etc., but howto change files within the root-file-system, as a new ex. /etc/hostname file... how to get changed/patched in build.
I got patches workking perfectly for u-bbot & kernel, but rootfs is a bit of a mystery for me...
br. Mike