Building Embedded Linux Systems, 2nd Edition

Chapter 5. Kernel Considerations

The kernel is the most fundamental software component of all Linux systems. It is responsible for managing the bare hardware within your chosen target system and bringing order to what would otherwise be a chaotic struggle between each of the many various software components on a typical system.

In essence, this means the kernel is a resource broker. It takes care of scheduling use of (and mediating access to) the available hardware resources within a particular Linux system. Resources managed by the kernel include system processor time given to programs, use of available RAM, and indirect access to a multitude of hardware devices—including those custom to your chosen target. The kernel provides a variety of software abstractions through which application programs can request access to system resources, without communicating with the hardware directly.

The precise capabilities provided by any particular build of the Linux kernel are configurable when that kernel is built. Kernel configuration allows you to remove support for unnecessary or obscure capabilities that will never be used. For example, it is possible to remove support for the many different networked filesystems from an embedded device that has no networking support. Conversely, it is possible to add support for a particular peripheral device unique to a chosen target system. Depending on their function, many capabilities can also be built into optional, runtime-loadable, modular components. ...