Linux+ Guide to Linux Certification, Third Edition

Week 8System Initialization and X Windows

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

Linux+ Guide to Linux Certification, 3e 2

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


The Boot Process POST (Power On Self Test): series of tests

run when computer initializesEnsures 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


The Boot Process (continued) /boot: directory containing kernel and

boot-related files Vmlinuz-<kernel version>: Linux kernel

file Daemon: system process that performs

useful taskse.g., printing, scheduling, OS maintenance

Init (initialize) daemon: first process started by Linux kernelLoads all other daemonsBrings system to usable state


The Boot Process (continued)


Figure 8-1: The boot process

Boot Loaders

Primary function: load Linux kernel into memory

Other functions:Passing information to kernel during startupBooting another OS: known as dual booting

Two most common boot loaders:GRand Unified Boot loader (GRUB)Linux Loader (LILO)


GRUB More common boot loader for modern

Linux Stage1: first major part of GRUB

Typically resides on MBRPoints to Stage1.5

Stage1.5: loads filesystem support and Stage2Resides in /boot/grub

Stage2: performs boot loader functions Displays graphical boot loader screenResides in /boot/grub


GRUB (continued)


Figure 8-2: GRUB boot loader screen

GRUB (continued) To configure, edit /boot/grub/grub.conf

Read directly by Stage2 boot loaderHDDs 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

loaderTo prevent, enable password protection

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


GRUB (continued)

If press any key during first five seconds after the BIOS POST get graphical GRUB boot menuManipulate the boot processGet a grub> prompt to enter commands

○ Help screen provides list of all available commands

grub-install command: installs GRUB boot loaderTypically for reinstallation when GRUB becomes

damaged


GRUB (continued)


Figure 8-5: Viewing help at the GRUB prompt

LILO

Stands for Linux Loader Traditional Linux boot loader

No longer supported by Fedora

Typically located on MBR Lilo boot: prompt appears following

BIOS POSTAllows choice of OS to load at startup

To configure, edit /etc/lilo.conf file


LILO (continued)


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

LILO (continued)

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


Dual Booting Linux

Normally only one OS may be used at a timeCan 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


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 directlyGRUB loads Windows boot loader from

Windows partitionLILO uses other= keyword to load boot loader

in appropriate partition


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


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

Using a Windows Boot Loader to Dual Boot Linux Use EasyBCD to add components to

Windows boot loaderWithin EasyBCD, use NeoGrub tab to modify

Windows boot loader to include Linux supportCopy 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


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


Figure 8-9: The EasyBCD program

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


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

Linux Initialization Kernel assumes control after Linux

loadedExecutes first daemon process (init daemon)

/etc/inittab: configuration file for init daemonUsed to determine number of daemons to be

loaded init daemon responsible for unloading

daemons when the system is halted or rebooted


Runlevels Runlevel: defines number and type of

daemons loaded into memory and executedinit daemon responsible for changing runlevels

○ Often called initstatesSeven standard runlevels

runlevel command: displays current and most recent runlevel

init command: change OS runleveltelinit command: Alias to init command


Runlevels (continued)


Table 8-3: Linux runlevels

The /etc/inittab File

Indicates default runlevel which the init daemon entersSyntax: id:5:initdefault:

Contains single uncommented line and series of explanatory comments


Runtime Configuration Scripts Runtime configuration (rc) scripts: scripts

that prepare the system, start daemons and bring system to usable stateExecuted 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


Runtime Configuration Scripts (continued) init daemon executes script for default

runlevel (5) /etc/rc.d/rc5 scriptExecutes 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


Runtime Configuration Scripts (continued) Message during system initialization

indicates whether each runtime configuration script has loaded successfullyHidden 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


Runtime Configuration Scripts (continued)


Figure 8-11: The Linux initialization process

Configuring Daemon Startup Most daemons started by init daemon from

symbolic links in /etc/rc.d/rc*.d directoriesPoint to daemon executable files in /etc/rc.d/init.d

Most daemons accept arguments start, stop, restartCan be used to manipulate daemons after

system startup service command: start, stop, or

restart daemons within /etc/rc.d/init.d directory


Configuring Daemon Startup (continued) To add daemons to be automatically

started:Add executable to /etc/rc.d/init.dCreate 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


The X Windows System: Linux GUI Components


Figure 8-15: Components of the Linux GUI

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 resultsNeed not run on same computer as X Windows

XFree86: OSS version of X WindowsOriginally intended for Intel x86 platform


Windows Managers and Desktop Environments Window manager: modifies look and feel

of X Windows Desktop environment: standard set of

GUI toolsWorks with a window manager to provide

standard GUI environmentProvides toolkits that speed up process of

creating new softwareKDE and GNOME are most common


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 LinuxMetacity window manager GTK+ toolkit

Can configure KDE or GNOME to use different window managere.g., compiz


Windows Managers and Desktop Environments (continued)


Figure 8-16: The KDE desktop environment

Windows Managers and Desktop Environments (continued)


Figure 8-17: The GNOME desktop environment

Starting and Stopping X Windows Runlevel 5 starts GNOME Display Manager

(GDM)Displays graphical login screenAllows user to choose the desktop environment

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


Starting and Stopping X Windows (continued) For runlevel 3:

Start gdm manually, orUse startx command

startx command: start X Windows and Window Manager or desktop environment specified in .xinitrc file in home directoryUsually points to .Xclients-default file


Configuring X Windows

X Windows interfaces with video hardwareRequires information regarding keyboard,

mouse, monitor, and video adapter card

Attempts to automatically detect required informationIf automatic detection fails, user needs to

specify correct hardware information manually


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 WindowsFiles can be edited manually or using a

program mouse-test command: detect mouse

Should be run as root user


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


Configuring X Windows (continued)


Figure 8-21: Selecting a keyboard layout



Figure 8-22: The Display Settings utility



Figure 8-23: Configuring video card and monitor model



Figure 8-24: Configuring dual display support



Figure 8-25: The xvidtune utility

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


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


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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Linux+ Guide to Linux Certification, Third Edition