# see http://wiki.debian.org/DebianInstaller/NetbootFirmware#Wheezy_Example_.232_:_add_debs_from_firmware.tar.gz
#!/bin/sh
FWTMP=/tmp/d-i_firmware
DSTDIR=/srv/tftp/boot/debian-installer/
rm -rf $FWTMP
mkdir  -p $FWTMP/firmware
cd $FWTMP

wget http://cdimage.debian.org/cdimage/unofficial/non-free/firmware/wheezy/current/firmware.tar.gz

tar -C firmware -zxf firmware.tar.gz

pax -x sv4cpio -s'%firmware%/firmware%' -w firmware | gzip -c >firmware.cpio.gz

for arch in i386 amd64; do
        # cd to the directory where you have your initrd
        cd $DSTDIR/$arch
        [ -f initrd.gz.orig ] || cp -p initrd.gz initrd.gz.orig
        cat initrd.gz.orig $FWTMP/firmware.cpio.gz > initrd.gz
done