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Linux+ Guide to Linux Certification, Third Edition. Chapter 8 System Initialization and X Windows. Objectives. Summarize the major steps necessary to boot a Linux system Configure the LILO and GRUB boot loaders

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Linux guide to linux certification third edition

Linux+ Guide to Linux Certification, Third Edition

Chapter 8

System Initialization and X Windows


Objectives

Objectives

  • Summarize the major steps necessary to boot a Linux system

  • Configure the LILO and GRUB boot loaders

  • Explain how the init daemon initializes the system at boot time into different runlevels

  • Configure the system to start daemons upon entering certain runlevels

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Objectives continued

Objectives (continued)

  • Explain the purpose of the major Linux GUI components: X Windows, window manager, and desktop environment

  • List common window managers and desktop environments used in Linux

  • Configure X Windows settings

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The boot process

The Boot Process

  • POST (Power On Self Test): series of tests run when computer initializes

    • Ensures functionality of hardware

  • MBR: defines partitions and boot loader

    • Normally located on first HDD sector

  • Boot loader: program used to load an OS

  • MBR might contain pointer to a partition containing a boot loader on the first sector

  • Active partition: partition pointed to by MBR

    • One per HDD

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The boot process continued

The Boot Process (continued)

  • /boot: directory containing kernel and boot-related files

  • Vmlinuz-<kernel version>: Linux kernel file

  • Daemon: system process that performs useful tasks

    • e.g., printing, scheduling, OS maintenance

  • Init (initialize) daemon: first process started by Linux kernel

    • Loads all other daemons

    • Brings system to usable state

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The boot process continued1

The Boot Process (continued)

Figure 8-1: The boot process

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Boot loaders

Boot Loaders

  • Primary function: load Linux kernel into memory

  • Other functions:

    • Passing information to kernel during startup

    • Booting another OS: known as dual booting

  • Two most common boot loaders:

    • GRand Unified Boot loader (GRUB)

    • Linux Loader (LILO)

Linux+ Guide to Linux Certification, 3e


Linux guide to linux certification third edition

GRUB

  • More common boot loader for modern Linux

  • Stage1: first major part of GRUB

    • Typically resides on MBR

    • Points to Stage1.5

  • Stage1.5: loads filesystem support and Stage2

    • Resides in /boot/grub

  • Stage2: performs boot loader functions

    • Displays graphical boot loader screen

    • Resides in /boot/grub

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Grub continued

GRUB (continued)

Figure 8-2: GRUB boot loader screen

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Grub continued1

GRUB (continued)

  • To configure, edit /boot/grub/grub.conf

    • Read directly by Stage2 boot loader

    • HDDs and partitions identified by numbers

      • Format: (hd<drive#>,<partition#>)

  • GRUB root partition: partition containing Stage2 boot loader and grub.conf file

  • GRUB normally allows manipulation of boot loader

    • To prevent, enable password protection

  • grub-md5-crypt command: generates encrypted password for use in grub.conf file

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Grub continued2

GRUB (continued)

  • If press any key during first five seconds after the BIOS POST get graphical GRUB boot menu

    • Manipulate the boot process

    • Get a grub> prompt to enter commands

      • Help screen provides list of all available commands

  • grub-install command: installs GRUB boot loader

    • Typically for reinstallation when GRUB becomes damaged

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Grub continued3

GRUB (continued)

Figure 8-5: Viewing help at the GRUB prompt

Linux+ Guide to Linux Certification, 3e


Linux guide to linux certification third edition

LILO

  • Stands for Linux Loader

  • Traditional Linux boot loader

    • No longer supported by Fedora

  • Typically located on MBR

  • Lilo boot: prompt appears following BIOS POST

    • Allows choice of OS to load at startup

  • To configure, edit /etc/lilo.conf file

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Lilo continued

LILO (continued)

Table 8-1: Common /etc/lilo.conf keywords

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Lilo continued1

LILO (continued)

Table 8-2: LILO error messages

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Lilo continued2

LILO (continued)

  • append= keyword (in /etc/lilo.conf): Useful for manually passing information to Linux kernel

    • Can pass almost any hardware information

      • Format is hardware dependent

  • Must reinstall LILO if /etc/lilo.conf file altered

  • lilo command: Reinstalls LILO

    • -u option: Uninstall LILO

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Dual booting linux

Dual Booting Linux

  • Normally only one OS may be used at a time

    • Can use virtualization software to run multiple OSs at the same time

  • Dual booting: configuration of boot loader which allows choice of OS at boot time

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Using grub or lilo to dual boot other operating systems

Using GRUB or LILO to Dual Boot Other Operating Systems

  • Easiest if Linux installed after another OS

    • Allows installation program to detect other OS

      • Place appropriate entries in boot loader configuration file

  • GRUB and LILO cannot load Windows Kernel directly

    • GRUB loads Windows boot loader from Windows partition

    • LILO uses other= keyword to load boot loader in appropriate partition

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Using grub or lilo to dual boot other operating systems continued

Using GRUB or LILO to Dual Boot Other Operating Systems (continued)

Figure 8-7: Configuring GRUB for a dual boot system

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Using a windows boot loader to dual boot linux

Using a Windows Boot Loader to Dual Boot Linux

  • Use EasyBCD to add components to Windows boot loader

    • Within EasyBCD, use NeoGrub tab to modify Windows boot loader to include Linux support

    • Copy contents of grub.conf into C:\NST\menu.lst

  • At next boot, Windows boot loader will prompt to choose between Windows and starting the NeoGrub loader to load the Linux OS

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Using a windows boot loader to dual boot linux continued

Using a Windows Boot Loader to Dual Boot Linux (continued)

Figure 8-9: The EasyBCD program

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Using a windows boot loader to dual boot linux continued1

Using a Windows Boot Loader to Dual Boot Linux (continued)

Figure 8-10: Booting Linux from a Windows boot loader

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Linux initialization

Linux Initialization

  • Kernel assumes control after Linux loaded

    • Executes first daemon process (init daemon)

  • /etc/inittab: configuration file for init daemon

    • Used to determine number of daemons to be loaded

  • init daemon responsible for unloading daemons when the system is halted or rebooted

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Runlevels

Runlevels

  • Runlevel: defines number and type of daemons loaded into memory and executed

    • init daemon responsible for changing runlevels

      • Often called initstates

    • Seven standard runlevels

  • runlevel command: displays current and most recent runlevel

  • init command: change OS runlevel

    • telinit command: Alias to init command

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Runlevels continued

Runlevels (continued)

Table 8-3: Linux runlevels

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The etc inittab file

The /etc/inittab File

  • Indicates default runlevel which the init daemon enters

    • Syntax: id:5:initdefault:

  • Contains single uncommented line and series of explanatory comments

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Runtime configuration scripts

Runtime Configuration Scripts

  • Runtime configuration (rc) scripts: scripts that prepare the system, start daemons and bring system to usable state

    • Executed by init daemon

  • At boot time, run /etc/rc.d/rc.sysinit script

    • Initialize the hardware components, set variables, check filesystems, and perform system tasks

  • dmesg command: shows output of hardware detection and /etc/rc.d/rc.sysinit script

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Runtime configuration scripts continued

Runtime Configuration Scripts (continued)

  • init daemon executes script for default runlevel (5) /etc/rc.d/rc5 script

    • Executes all files that start with S or K in the /etc/rc.d/rc5.d directory

      • Each file is symbolic link to script for starting or stopping daemon

      • S/K indicate Start/Kill daemon upon entering the runlevel

  • When user specifies runlevel1, init daemon runs default script but executes files in the /etc/rc.d/rc1.d directory

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Runtime configuration scripts continued1

Runtime Configuration Scripts (continued)

  • Message during system initialization indicates whether each runtime configuration script has loaded successfully

    • Hidden by graphical boot screen display

      • Use Esc key to remove the graphical screen

  • Output of runtime configuration scripts is logged to the /var/log/messages file

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Runtime configuration scripts continued2

Runtime Configuration Scripts (continued)

Figure 8-11: The Linux initialization process

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Configuring daemon startup

Configuring Daemon Startup

  • Most daemons started by init daemon from symbolic links in /etc/rc.d/rc*.d directories

    • Point to daemon executable files in /etc/rc.d/init.d

  • Most daemons accept arguments start, stop, restart

    • Can be used to manipulate daemons after system startup

  • service command: start, stop, or restart daemons within /etc/rc.d/init.d directory

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Configuring daemon startup continued

Configuring Daemon Startup (continued)

  • To add daemons to be automatically started:

    • Add executable to /etc/rc.d/init.d

    • Create appropriate links to /etc/rc.d/rc*.d

  • chkconfig command: view and modify daemons that are started in each runlevel

  • ntsysv utility: modifies file entries in /etc/rc.d/rc*.d directories

  • Service Configuration utility: easiest way to control daemon startup by runlevel

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The x windows system linux gui components

The X Windows System: Linux GUI Components

Figure 8-15: Components of the Linux GUI

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X windows

X Windows

  • X Windows: core component of Linux GUI

    • Provides ability to draw graphical images in windows that are displayed on terminal screen

    • Sometimes referred to as X server

  • X client: programs that tell X Windows how to draw the graphics and display the results

    • Need not run on same computer as X Windows

  • XFree86: OSS version of X Windows

    • Originally intended for Intel x86 platform

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Windows managers and desktop environments

Windows Managers and Desktop Environments

  • Window manager: modifies look and feel of X Windows

  • Desktop environment: standard set of GUI tools

    • Works with a window manager to provide standard GUI environment

    • Provides toolkits that speed up process of creating new software

    • KDE and GNOME are most common

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Windows managers and desktop environments continued

Windows Managers and Desktop Environments (continued)

  • K Windows Manager (kwm): window manager that works under KDE

  • Qt toolkit: software toolkit used with KDE

  • GNOME desktop environment: default desktop environment in Fedora Linux

    • Metacity window manager

    • GTK+ toolkit

  • Can configure KDE or GNOME to use different window manager

    • e.g., compiz

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Windows managers and desktop environments continued1

Windows Managers and Desktop Environments (continued)

Table 8-4: Common window managers

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Windows managers and desktop environments continued2

Windows Managers and Desktop Environments (continued)

Figure 8-16: The KDE desktop environment

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Windows managers and desktop environments continued3

Windows Managers and Desktop Environments (continued)

Figure 8-17: The GNOME desktop environment

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Starting and stopping x windows

Starting and Stopping X Windows

  • Runlevel 5 starts GNOME Display Manager (GDM)

    • Displays graphical login screen

    • Allows user to choose the desktop environment

  • .dmrc file: contains desktop environments that were manually selected in a session menu

    • By default, root user is not allowed to log into system using GDM

      • To change this, edit /etc/pam.d/gdm and /etc/pam.d/gdm-password files

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Starting and stopping x windows continued

Starting and Stopping X Windows (continued)

  • For runlevel 3:

    • Start gdm manually, or

    • Use startx command

  • startx command: start X Windows and Window Manager or desktop environment specified in .xinitrc file in home directory

    • Usually points to .Xclients-default file

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Configuring x windows

Configuring X Windows

  • X Windows interfaces with video hardware

    • Requires information regarding keyboard, mouse, monitor, and video adapter card

  • Attempts to automatically detect required information

    • If automatic detection fails, user needs to specify correct hardware information manually

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Configuring x windows continued

Configuring X Windows (continued)

  • Mouse, keyboard, monitor, and video adapter card information stored in a file

    • /etc/X11/xorg.conf file for X.org implementation of X Windows

    • /etc/X11/XF86Config file for XFree86 implementation of X Windows

    • Files can be edited manually or using a program

  • mouse-test command: detect mouse

    • Should be run as root user

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Configuring x windows continued1

Configuring X Windows (continued)

  • system-config-keyboard command: start the Keyboard tool in order to configure keyboard

  • system-config-display command: start the Display Settings utility to configure video adapter card

  • xvidtune utility: fine-tune the vsync and hsync of the video card and monitor

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Configuring x windows continued2

Configuring X Windows (continued)

Figure 8-21: Selecting a keyboard layout

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Configuring x windows continued3

Configuring X Windows (continued)

Figure 8-22: The Display Settings utility

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Configuring x windows continued4

Configuring X Windows (continued)

Figure 8-23: Configuring video card and monitor model

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Configuring x windows continued5

Configuring X Windows (continued)

Figure 8-24: Configuring dual display support

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Configuring x windows continued6

Configuring X Windows (continued)

Figure 8-25: The xvidtune utility

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Summary

Summary

  • Boot loaders are typically loaded by the system BIOS from the MBR or the first sector of the active partition of a hard disk

  • The boot loader is responsible for loading the Linux kernel and to boot other OSs in a dual boot configuration

  • The GRUB boot loader uses the /boot/grub/grub.conf configuration file and the LILO boot loader uses the /etc/lilo.conf configuration file

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Summary continued

Summary (continued)

  • Seven standard runlevels are used to categorize a Linux system based on the number and type of daemons loaded in memory

  • The init daemon is responsible for loading and unloading daemons when switching between runlevels

  • Daemons are typically stored in the /etc/rc.d/init.d directory and loaded at system startup from entries in the /etc/rc.d/rc*.d directories

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Summary continued1

Summary (continued)

  • The Linux GUI has several interchangeable components: X server, X clients, Window Manager, and optional desktop environment

  • X Windows is the core component of the Linux GUI that draws graphics to the terminal screen

  • You can start the Linux GUI from runlevel 3 by typing startx at a command prompt, or from runlevel 5 by using the gdm

  • The hardware information required by X windows is automatically detected, but can be modified

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