Publisher Summary This chapter highlights kernel, which is the core of the FreeBSD operating system. It is responsible for managing resources, enforcing security, networking, and disk access. The default kernel is located in the file /kernel. In the design and development of an embedded system, disk space and memory are critical resources. Unlike a typical desktop computer packed with random-access memory and disk space, an embedded computer only needs minimal support to perform its task, with respect to software and hardware. During FreeBSD installation, a kernel is installed on the computer, which is called the “GENERIC kernel.” The GENERIC kernel is created to support as many computers and configurations as possible to simplify the installation process. The chapter also discusses the way to configure and build a custom FreeBSD kernel to suit the hardware and digital input-output application.