So far, we have seen an overview of the suite of tools we need to create a custom ROM from a binary system image. The most important of all is the kitchen, and it needs system.img and boot.img partition files to properly do its job.

If you are targeting Google devices, this is an easy game. Google provides system source code for its devices, so we can always build our .img files from the source, as we learned in previous chapters. We can also grab the .img files from the official system installation packages that Google also provides for its devices at every new release of the Android system.

If you are targeting a device that's not a Nexus, things become more adventurous. Most of the time you don't have the system source code; often you don't even have the downloadable system images. As you will see in the next sections, there is always a way to obtain every last piece of the puzzle to create our custom ROM.