• make mountdir sudo mkdir /media/$USER/bla
• open img file whit sudo kpartx -a <raspian.img>
• mount sudo mount /dev/mapper/loop0p2 /media/$USER/bla
• go to mountdir cd /media/$USER/bla
• edit content as root and save (may edit /etc/rc.local as shown in next step)
• go out of mountdir cd
• sync
• umount sudo umount /media/$USER/bla
• close img file whit sudo kpartx -d <raspian.img>
• sync
• rm mountdir sudo rm -r /media/$USER/bla

add the folowing to /etc/rc.local to auto load and run the configfiles on startup:

wget https://github.com/dog42/pizerow/archive/master.zip -O /home/pi/.master.zip unzip /home/pi/.master.zip -d /home/pi/.piconf rm /home/pi/.master.zip ./home/pi/.piconf/pizerow-master/go.sh