We will now begin our journey of learning how the Yocto Project's engine works behind the scenes. As with every journey, communication is critical, so we need to learn the language used by the Yocto Project's tools and learn how to get the best out of these tools in order to accomplish our goals.

In the preceding chapters, we were introduced to the standard Yocto Project workflow for creating and emulating images. Now, in this chapter, we will explore the concept of metadata, see how recipes depend on each other, and how those recipes are used by Poky.

Besides the dependencies, there are other aspects that are important for every recipe. From downloading source code to generating images, there is a huge list of tasks, such as storing the source code in the directory used for the build; patching, configuring, compiling, installing, and generating the packages; and determining how the packages fit into the generated images.