Last checked against version &kernel-contversion;. The Linux kernel is at the core of every Linux system. It's what makes Linux tick. When a computer is turned on and boots a Linux system, the very first piece of Linux software that gets loaded is the kernel. The kernel initializes the system's hardware components: serial ports, parallel ports, sound cards, network cards, IDE controllers, SCSI controllers and a lot more. In a nutshell the kernel makes the hardware available so that the software can run. These are the files we copy to /usr/include/{linux,asm} in Chapter 6. They should match those which glibc was compiled against and therefore should not be replaced when upgrading the kernel. They are essential for compiling many programs.