Linux Kernel Development

Part 1


Sameer Rahmani

Chapter 1



  • What is Linux Kernel ?
  • Why I need to learn about Kernel ?
  • Linux Kernel development process
  • Basic Linux Kernel internals

What is kernel anyway?

Kernel is responsible for communicating 
with hardware

Kernel Provide a unique interface for
 software to use hardware 

Kernel is responsible to handle network

Kernel schedule processes to use CPU time

Kernel shares resources between processes

Very Basic Schema of an operating system

Why softwares needs


  • Without a kernel each software should implement its own interface to use hardware
  • With lots of interfaces around there will be huge number of software bugs around.
  • There is no warranty for each interface performance 

Why do i need to know about


  • You can improve your system performance
  • You can install some device drivers by yourself *
  • It's good to know about your Linux box
  • If you are a developer or want to be one you have to know how your operating system operate.

Why Linux Kernel ?

  • It's totally free ( under GPL v2)
  • Monolithic with support for loadable modules
  • True multi-tasking
  • Support for hardware and filesystem
  • Multi-arch
  • Robust community 
  • People watching, So no backdoor
  • Configurable
  • ........

that's Enough, let's begin

First Step

Build a custom kernel

Requirements for build

1. Linux kernel source code. Get it from
$ wget 

2. A bootloader. You definitely have one already.

3.ncurses library and build tools          (on a debian box)
# apt-get install libncurses5 build-essential 

Lets Do it

Extract the source code.
$ tar Jxvf linux-3.x.y.tar.xz  
Create a build directoy
$ mkdir build 
Configure the kernel  ( It's the hard part )
$ cd linux-3.x.y && make O=../build menuconfig 
build the kernel
$ make O=../build -j 4 


Install new kernel image
# make O=../build modules_install install 

update your bootloader configuration to load new image.
# update-grub2 
* In case of a grub2 bootloader on a debian compatible box

Reboot & Enjoy new kernel

Initial Ram disk

Installer script probably created it for you.

Manual creation of initrd:

# cd /boot/ && mkinitramfs -v -o ./initrd-3.x.y 3.x.y 


Start up Process

BIOS -> Bootloader -> Kernel


BIOS performs hardware-platform specific
 startup tasks

BIOS loads and executes the partition boot code
 from the designated boot device
(Phase 1 of a Linux bootloader)


Phase 1 loads phase 2 (the bulk of the boot loader code).

Some bootloaders use a phase called "Phase 1.5"
Without is some lard modern disks may not be 
fully available.

Decompress OS into memory and load it.

Prepare hardware and memory before calling


'start_kernel()' perform OS setup
( Interrupts, Memory management, Drivers, etc )

Kernel spawns idle process, scheduler and init process

init process setup and load the user space world

Wait until next chapter To learn about startup process in nutshell 

End of Chapter 1


  • Linux Kernel Development (3rd Edition) ISBN: 978-0672329463
  • Linux kernel documentation (documents directory in source tree)

Contact me

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twitter:          @lxsameer

Linux Kernel Development

By Sameer Rahmani

Linux Kernel Development

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