Introduction to Linux Kernel Programming

The Linux kernel is designed as a mixture of a monolithic binary image and a micro-kernel.  This combination allows for the best of both worlds.  On the monolithic side, all the code for the kernel to work with the user and hardware is already installed and ready for fast access, but the downside is that to add more functionality you need to rebuild the entire kernel.   In a different manner, a micro-kernel is composed of small pieces  of code that can be meshed today and more pieces can be added or removed as needed.  However, the downside to micro-kernel is a slower performance.

Adding a module to the Kernel

Linux is organized as both monolithic, one huge binary, and micro-kernel, as you can add more functionality to it.  The process of adding more functionality to the kernel can be illustrated by the crude image to the left.

The process begins by using the command insmod with the name of the kernel module you want (which usually ends with extension *.ko).  From here, the module registers itself the the kernel which serves to allow the kernel to know which module to invoke when it needs to handle a request from the user.  Finally, when usage of the module is complete, use rmmod to remove the module.

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Quick Shell Commands

insert a module into the kernel

insmod [name_of_module]     

remove a module from the kernel

rmmod [name_of_module]   

list all running modules

lsmod                                       

display message of printk

dmesg