Linux Kernel

 The Linux Kernel  It’s loaded at initial bootup of Linux system, manages activities : I/O, memory, processes, network interface,…  Why would you want to build a new kernel?. newer ha

 Demonstrate new kernel preparation

 Recompile and install a kernel

 Configure LILO to use a new kernel

 The Linux Kernel

 It’s loaded at initial bootup of Linux system,

manages activities : I/O, memory, processes, network interface,…

 Why would you want to build a new kernel ?

(newer hardware, faster, more stable, …)

 Kernel can be built with 2 basic options :

• Device drivers can be built directly into the kernel binary itself

• Device drivers can be built as external modules to the kernel

 Kernel Version Numbering

basic components:

- The major number

- The minor number

- The micro number (patch number)

There is the fourth number, sometimes

applied after a dash is genarally the patch

level , applied by kernel maintainers

 Kernel Version Numbering

- The minor number is even = stable version

- The minor number is odd = development ver.

- A patch constitutes a more precise measurement of the kernel version All patchs to the kernel are cumulative You simply have to

obtain and apply the latest patch for the kernel

to be sure you have the most up-to-date patched support

# uname -r

 Recent Kernel Changes

- Itanium and X86-64 AMD Hamer CPU support

- Improve PnP/hot swappable device regconition

- Journaling file systems : ext3, ReiserFS,

- …

 The source tree (source code)

 Apply patches to the kernel source code

 make : determines which pieces of a large

program need to be recompiled and compile them It executes commands in Makefile (sometime named makefile) to update

programs or module components

 C/gcc : C compiler integrated into gcc

 binutils: a collection of binary utilities :

gas(assembler),ld(likner),

nm, ranlib, objdump, …

 The Source Tree

extension of tar.gz or tar.bz2

Ex: linux-2.4.19-16.tar.gz

 You should NEVER unpack your kernel

sources directly into /usr/src/linux

# mkdir /usr/src/linux-2.4.19-16

# tar xzfv linux-2.4.19-16.tar.gz –C

/usr/src/linux-2.4.19-16

 The Source Tree

 Subdirectories in the source tree : /usr/src/linux-2.4.19-16/

Documentation arch

drivers fs

include init

ipc

kernel lib

mm modules net

scripts

 This is the structure that most kernel sources will follow

 Apply patches to kernel source

 A patch file is editing instructions to change one set of files into new version of the files

Ex: patch-2.4.19-16-1-acl.gz

 Steps to patch :

# ln –s /usr/src/linux-2.4.19-16 \

/usr/src/ linux

# cp patch-2.4.19-16-1-acl /usr/src/linux

# cd /usr/src/linux

# cat patch-2.4.19-16-1-acl | patch -pl

 Customize & Install New Kernel

the Linux kernel Makefile that can be

used to build kernel :

make dep Build a list of all kernel deps *

make clean Remove old binaries and o files *

image and update LILO

make zImage Make a simple compressed image

make bzImage Build an image compressed with

gzip *

 General Procedure to build kernel

Step 1: Configure kernel’s parameters and build it

xconfig

- make dep, make clean, make bzImage

Step 2: Copy new kernel from arch/i386/boot/

bzImage to /boot/vmlinuz-2.4.19-16

Step 3: Copy Sytem.map to

/boot/System.map-2.4.19-16

 General Procedure to build kernel

Step 4: Copy config to

/boot/config-2.4.19-16

Step 5: Type make module

Step 6: Type make module_install

Step 7: Edit /etc/lilo.conf to make an new

entry to your new kernel

customize module loadtime parameters in

/etc/modules.conf or /etc/conf.modules

a stack of dependent modules or all modules that are marked with a specified tag

required of running kernel.You can put it in

start-up script and run depmod –a

( Package : modutils )

 Building a Monolithic Kernel

the new kernel referred monolithic kernel

 In kernel configuration, a “Y”answer for an option means to build that option into the kernel (monolithic); a “N” means exclude and “M” means to build as a module.

modules_install when building a new kernel

 Boot Loader Features & Config

 LILO (Linux Loader)

 How to install ?

- Install LILO manually from the packet

- Let your Linux automatically install LILO

 Where to install ? – first 1024 logical cylinders

- On a diskette

- In the boot sector of a primary or logical Linux partition on the first harddisk

- In the Master Boot Record

 You must run /sbin/lilo to update the

configuration in file /etc/lilo.conf

 LILO Configuration File

[root@lpi linux-2.4]# more /etc/lilo.conf

 Using LILO to Test a New Kernel

your new kernel :

…

image=/boot/vmlinuz-2.4.19-16

label=My New Kernel read-only

 LILO and Boot Options

See #man lilo

See #man lilo.conf and go to

“KERNEL OPTIONS” category

 Demonstrate new kernel preparation

 Recompile and install a kernel

 Configure LILO to use a new kernel