How to unpack, modify, pack and flash `system.img.ext4` file using Odin?

Question

I have a system.img.ext4.lz4 file that is compatible with my Samsung S10 5G(Qualcomm) device. I have extracted system.img.ext4 file from the system.img.ext4.lz4 using unlz4 system.img.ext4.lz4 command.

I want to play with its content. So I have decided it in two steps:

1. Flash system.img.ext4 without modification:

   • Using tar -cvf AP.tar system.img.ext4 command, I have created a AP.tar file.
   • Flashed AP.tar file using Odin3 v3.13.
   • It flashed successfully.

2. Flash system.img.ext4 with modification:

a) Modifying

• With simg2img system.img.ext4 system.img, you will get a raw image file named system.img
• With mkdir system, create directory to mount system.img
• With sudo mount -t ext4 -o loop system.img system/ you will get all files of system.img in system folder
• With ls -l system/init.rc note permissions: 750
• With sudo chmod 777 system/init.rc give write permissions
• With sudo echo "#MODIFICATION " >> system/init.rc done some modification in init.rc
• With sudo chmod 750 init.rc reset init.rc to the noted permissions

b) Calculate system sector size

• With tune2fs -l system.img | grep "Block size\|Block count" you will get block size and count
• With echo $((1553064 * 4096)) multiply both results. I got 6361350144

c) Packing

• With sudo make_ext4fs -s -l 6361350144 -a system system_new.img sys/ you will get system_new.img “Android Sparse Image” that has all changes
• With sudo umount system unmount the system directory
• With rm -fr system delete the system directory

d) Tar Compression

• With rm system.img.ext4 remove original system.img.ext4, Don’t worry you should have a backup of it in lz4 file
• With mv system_new.img system.img.ext4 rename system_new.img to system.img.ext4 for flashing with Odin3 v3.13
• With tar -cvf AP.tar system.img.ext4 you will get AP.tar that you can flash with Odin3 v3.13.
• It failed to flash with FAIL! (Auth) error.

Please suggest how can I resolve this issue? I will be very thankful to you for any little to big suggestion.

Answer 1

You cannot resolve this error. It's simple why. It's a modified .IMG file. Since you have a Qualcomm Snapdragon, you are not allowed to flash custom/modified software onto your phone. Reason being is because it's bootloader is locked. There is no way for you to unlock it. The reason the one called AP.IMG worked, is because it wasn't modified at all.