A kernel module is a code that can be loaded into the kernel image at will, without requiring users to rebuild the kernel or reboot their computer. Modular design ensures that you do not have to make a monolithic kernel that contains all code necessary for hardware and situations.

Common kernel modules are device drivers, which directly access computer and peripheral hardware.

Kernel modules have a .ko extension.

⚲ API

/proc/modules

man 8 insmod – simple program to insert a module

man 8 modprobe – searches and loads a module with dependencies

/etc/modprobe.d/

/lib/modules/$(uname -r)/modules.dep – module dependencies, is created by depmod -a

man 8 lsmod – list loaded modules

man 8 kmod – core program to manage Linux Kernel modules

man 8 modinfo

linux/init.h _inc – initcalls

linux/module.h _inc – macros and functions for kernel module support

module_init _id – module initialization entry point

module_exit _id – module initialization exit point

MODULE_LICENSE _id – licence declaration

linux/mod_devicetable.h _inc – device ID tables for module device matching

linux/export.h _inc – macros for symbol export control to kernel modules.

linux/kernel.h _inc – miscellaneous stuff

⚙️ Internals

kernel/module _src

📖 References

Building External Modules _doc

📚 Further reading

Loadable kernel module

The Linux Kernel Module Programming Guide

https://wiki.archlinux.org/title/Kernel_module

Linux Driver Template

http://lwn.net/images/pdf/LDD3/ch02.pdf

http://www.xml.com/ldd/chapter/book/ch02.html

Managing kernel modules, RHEL

http://www.tldp.org/LDP/tlk/modules/modules.html