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

问题

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.

来源：https://stackoverflow.com/questions/58541074/how-to-unpack-modify-pack-and-flash-system-img-ext4-file-using-odin