UF-Instant firmware patching script

build.sh

#!/bin/bash -xe
OLT_FW=https://dl.ui.com/firmwares/ufiber/UF-OLT.v4.3.1.3909.210421.0814.tar
GPON_SN=ZTEG01020304
GPON_SN_RAW=5a54454701020304
GPON_MAC=01:02:03:04:05:06

[ $UID != 0 ] && echo "You need to be root" && exit 1

wget -O UF-OLT.tar $OLT_FW
mkdir oltfw
(
    cd oltfw
    tar -xf ../UF-OLT.tar
    unsquashfs squashfs.tmp
    mv squashfs-root/usr/share/onufw/UF-ONU.UF-INSTANT.* ../
)
rm -rf oltfw UF-OLT.tar

FW_NAME_GLOB=(UF-ONU.UF-INSTANT.*)
FW_NAME="${FW_NAME_GLOB[0]%.img}"

rm -rf $FW_NAME $FW_NAME.mod* $FW_NAME.tar

tail -c +57 $FW_NAME.img >$FW_NAME.tar
mkdir $FW_NAME
(
    cd $FW_NAME
    tar -xf ../$FW_NAME.tar
    unsquashfs rootfs
    sed -i "s/%c%c%c%c%02x%02x%02x%02x/$GPON_SN\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00/" squashfs-root/lib/modules/ubnthal.ko
    sed -i "s/%02x%02x%02x%02x%02x%02x%02x%02x/$GPON_SN_RAW\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00/" squashfs-root/lib/modules/ubnthal.ko
    perl -pi -e "s/%02x:%02x:%02x:%02x:%02x:%02x\n/$GPON_MAC\n\0\0\0\0\0\0\0\0\0\0\0\0/" squashfs-root/lib/modules/ubnthal.ko
    mksquashfs squashfs-root rootfs.mod -comp lzma -always-use-fragments -b 131072
    mv rootfs.mod rootfs
    chmod 700 rootfs
    md5sum $(cut -d' ' -f3 <md5.txt | xargs) >md5.mod.txt
    mv md5.mod.txt md5.txt

    tar -cf ../$FW_NAME.mod.tar --owner=builder:1000 --group=builder:1000 $(tar -tf ../$FW_NAME.tar | xargs)
)

{
    printf 'UBNT.ONU'
    for _ in $(seq 1 27); do printf '\x00'; done
    printf '\x01\x00\x00\x00\x00'
    printf '%08x\n' $(($(stat -c %s "$FW_NAME.mod.tar") + 56)) | xxd -r -p
    printf '\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\xee\xc6'
    cat $FW_NAME.mod.tar
} >$FW_NAME.mod.img

CKSUM=$(crc32 $FW_NAME.mod.img)
echo "$CKSUM" | xxd -r -p | dd bs=1 seek=44 of=$FW_NAME.mod.img conv=notrunc

rm -rf $FW_NAME $FW_NAME.img $FW_NAME.mod.tar $FW_NAME.tar

Could someone please help me to update following entry in ubnthal.ko?

[cat /proc/ubnthal/model]
UF-Instant

sed -i "s/UF-Instant/$GPON_MODEL/" squashfs-root/lib/modules/ubnthal.ko

Did not worked. It made ubnthal directory never created.