Ch11 Kernel

8/9/2019 Ch11 Kernel

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SAIGONLAB 69-3 Nguyen Thi Nho, P9, Q.TBinh, Tp. HCM LPI 102

SAIGONLAB 83 Nguyn Th Nh, P9, Q.Tn Bnh, Tp. HCM LPI 102

Objectives

Define kernel properties

Demonstrate new kernel preparation

Identify and use kernel configuration tools

Recompile and install a kernel

Identify kernel modules

Configure LILO to use a new kernel


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The Linux Kernel

Its loaded at initial bootup of Linux system,manages activities : I/O, memory, processes, networkinterface,

Why would you want to build a new kernel ?(newer hardware, faster, more stable, )

Kernel can be built with 2 basic options :

D

evice drivers can be built directly into thekernel binary itself (monolithic)

Device drivers can be built as external modulesto the kernel (modular)


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Kernel Version Numbering

Kernel version numbers are made by three basiccomponents:

The major number

The minor number

The micro number (patch number)

There is the fourth number, sometimes appliedafter a dash is genarally the patch level, applied bykernel maintainers

Ex : 2 . 4 . 7 - 10


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SAIGONLAB 69-3 Nguyen Thi Nho, P9, Q.TBinh, Tp. HCM LPI 102SAIGONLAB 83 Nguyn Th Nh, P9, Q.Tn Bnh, Tp. HCM LPI 102

Preparing For The New Kernel

See

/usr/src/linux/Documentation/Changes

Software tools

The source tree (source code)

Apply patches to the kernel source code


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Software Tools

make : determines which pieces of a large program

need to be recompiled and compile them. It executescommands 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,


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The Source Tree

Kernel source released as a zipped tar file,

extension of .tar.gz or .tar.bz2Ex: linux-2.4.19-16.tar.gz

You should NEVER unpack your kernel sourcesdirectly into /usr/src/linux

# tar xzfv linux-2.4.19-16.tar.gz C /usr/src


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Apply patches to kernel source

A patch file is editing instructions to change one setof files into new version of the files Ex: patch-2.4.19-

16-1-acl.gzSteps 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 p1


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Customize & Install New Kernel

There are many possible make targets in the Linuxkernel Makefile that can be used to build kernel :

make depB

uild a list of all kernel depsmake clean Remove old binaries and .o files

make zlilo Make a compressed vmlinuz

image and update LILOmake zImage Make a simple compressed image

make bzImage Build an image compressed with gzip


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General Procedure to build kernel

Step 1: Configure kernels parameters and build it

make config or make menuconfig or makexconfig

make dep, make clean, make bzImage


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General Procedure to build kernel

Step 2: Compile modules

make modules

Step 3: Install modulesmake modules_install

Step 4: Install kernel

make installStep 5: Check boot loader configuration

Step 6: Backup file .config


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make menuconfig Interface


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make xconfig Interface


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KernelDefault Option with rdev

With rdev or its new name rootflags , you can setdefault option appended to your new kernel imagewithout add them to /etc/lilo.conf

( See #man rdev for more information )


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Kernel Modules

insmod Install & binding a module to kernel.You can customizemodule loadtime parameters in /etc/modules.conf or /etc/conf.modules

rmmod Unload a module from kernel

lsmod List currently loaded modules in kernelmodinfo Details about a modules description

genksyms Generates symbol version information

modprobe Load a set of modules either a single module, a stack of

dependent modules or all modules that are marked with a specified tagdepmod Build a relationship table for modules that are required ofrunning kernel.You can put it in start-up script and run depmod a

( Package : modutils )


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Building a Monolithic Kernel

If you build all supports directly into kernel, thenew kernel referred monolithic kernel

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

You can omit make modules and makemodules_install when building a new kernel


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Boot Loader Features & Config

LILO (Linux Loader)How to install ?

Install LILO manually from the packet

Let your Linux automatically install LILOWhere to install ? first 1024 logical cylinders

On a diskette

In the boot sectorof a primary or logical Linuxpartition on thefirstharddisk

In the Master Boot Record

You must run /sbin/lilo to update the configurationin file /etc/lilo.conf


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LILO Configuration File

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

timeout=50

default=linux

boot=/dev/hda

root=/dev/hda1

message=/boot/message

image=/boot/vmlinuz-2.4.7-10

label=linux

read-only


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Using LILO to Test a New Kernel

Make new entry in /etc/lilo.conf for your newkernel :

image=/boot/vmlinuz-2.4.19-16

label=My New Kernel

read-onlyRun /sbin/lilo v command *

Boot with new kernel and observe


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LILO and Boot Options

LILO command options

See #man lilo

Boot options

See #man lilo.conf and go to

KERNEL OPTIONS category


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GRUB (GRand and Unified nified Bootloader)

GRUB can boot multiple OS and quickly gaining popularity, maysoon replace LILO

How to install ?

Install GRUB manually

Let your Linux automatically install GRUB

Where to install ? first 1024 logical cylinders

On a diskette

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

In the Master Boot Record

You DONT need to run /sbin/grub to update the configurationin file /etc/grub.conf


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LOADLIN

Its a MS-DOS program that can launch a Linuxkernel from DOS prompt.This is very useful if youhave hardware that relies on MS-DOS driver.

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Ch11 Kernel