With hardware-specific changes on their way, the next step is customizing the target root filesystem, the software that runs under the Linux kernel, also called the Linux user space.

The usual approach to this is to start with one of the available core images and both optimize and customize it as per the needs of your embedded project. Usually, the images chosen as a starting point are either core-image-base for a headless system, or core-image-sato for a graphical system, but any of them will do.

This chapter will show you how to add a software layer to contain those changes, and will explain some of the common customizations made, such as size optimization. It will also show you how to add new packages to your root filesystem, including licensing considerations.