I am doing this because this is the easiest way to create an EXT4 image.
This is not my guide I am just adapting and make it clear to everybody; someone showed me how to do this (I will mention him at the end of the guide).
Let's assume that you dumped the system.img from your own device and you want to add something to it.
We will create a new system.img and we will name it system_new.img, the size will be 240 Mb.
Linux Machine (I used Ubuntu)
We prepare the directories and copy the system.img in the folder in which we will work.
mkdir system (here we will mount the old system.img
mkdir system_new (here we will mount the system_new.img)
Step 2 – Creation of the actual EXT4.img
dd if=/dev/zero of=system_new.img bs=4k count=60000
Translation of the terms,
bs =blocksize, 4k= the size of the block`s which in this case is 4kb
count=60000, the number of block`s, in our case will result an image of 240 Mb.
The blocksize can be 1k/2k/4k/16k
To get the exact size of the image that you create use simple maths.
60000 * 4 = 240000
Step 3 Formating the system_new.img with EXT4
It will be a question where you will select yes (Y)
We override the file system check (If you don`t do this, the image will not work)
tune2fs -c0 -i0 system_new.img
Step 4 We mount the directories that we previous created.
mount -o loop system_new.img system_new/
mount -o loop system_new.img system/
Step 5 We copy the content from the old system.img in the system_new.img
cp -v -r -p system/* system_new/
We sync the files
Step 6 Unmounting the partitons.
Step 7 Enjoy your new ext4 system.img
If you are using Ubuntu just type
And you will be root and no more sudo at each command.
You can add new files in the new created system.img but you need to set the permissions and ownership properly, otherwise it will not work.
Credits: arctablet.com administrator.