For this project system_unlocked.img is being modified

Prerequisite

• ubireader
• mkfs.ubifs and ubinize (search, how to install it)

Unpack

unpack system_unlocked.img

ubireader_extract_images system_unlocked.img -o system_u
cd ./system_u/system_unlocked.img/

Now you will get file with .ubifs In my case its "img-35657280_vol-rootfs.ubifs"

unpack ubifs

ubireader_extract_files -k -o ./rootfs img-35657280_vol-rootfs.ubifs

Repack

repack .ubifs

mkfs.ubifs -m 2048 -e 126976 -c 1073 -x lzo -f 8 -k r5 -p 1 -l 5 -F -r ./rootfs/ rootfs.ubivol

setting up config.ini

touch config.ini
echo "[rootfs-volume]
mode=ubi
image=rootfs.ubivol
vol_id=0
vol_size=27807744
vol_type=dynamic
vol_name=rootfs" > config.ini

if vol_size=27807744 try vol_size=26791936

Repack to img

ubinize -p 131072 -m 2048 -o system_m.img ./config.ini