1.2.1. Loadable modules
One of the many nice features of Linux is the ability to extend features provided by the kernel at runtime. This means that you can add features to the kernel (and remove them) while the system is running.
Each piece of code that can be added to the kernel at runtime is called a module. The Linux kernel provides support for many module types, including but not limited to, device drivers. Each module consists of object code (not linked into a complete executable file), can be dynamically linked into the running kernel, through the insmod program, and through the rmmod program to link.
The division of graph kernels represents different categories of modules responsible for specific tasks, and a module belongs to a particular category according to the functionality it provides. The arrangement of modules in the division of graph kernels covers the most important categories, but is far from Complete, because more and more functions are modularized in Linux.
Figure 1.1. The division of the kernel
