Linux Guide to Linux Certification, Third Edition

1
Linux Guide to Linux Certification, Third Edition

• Week 8
• System Initialization and X Windows

2
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

3
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

4
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

5
The Boot Process (continued)

• /boot directory containing kernel and
  boot-related files
• Vmlinuz-ltkernel versiongt 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

6
The Boot Process (continued)

Figure 8-1 The boot process
7
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)

8
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

9
GRUB (continued)
Figure 8-2 GRUB boot loader screen
10
GRUB (continued)

• To configure, edit /boot/grub/grub.conf
• Read directly by Stage2 boot loader
• HDDs and partitions identified by numbers
• Format (hdltdrivegt,ltpartitiongt)
• 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

11
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 grubgt 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

12
GRUB (continued)
Figure 8-5 Viewing help at the GRUB prompt
13
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

14
LILO (continued)

Table 8-1 Common /etc/lilo.conf keywords
15
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

16
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

17
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

18
Using GRUB or LILO to Dual Boot Other Operating
Systems (continued)
Figure 8-7 Configuring GRUB for a dual boot
system
19
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

20
Using a Windows Boot Loader to Dual Boot Linux
(continued)
Figure 8-9 The EasyBCD program
21
Using a Windows Boot Loader to Dual Boot Linux
(continued)
Figure 8-10 Booting Linux from a Windows boot
loader
22
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

23
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

24
Runlevels (continued)
Table 8-3 Linux runlevels
25
The /etc/inittab File

• Indicates default runlevel which the init daemon
  enters
• Syntax id5initdefault
• Contains single uncommented line and series of
  explanatory comments

26
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

27
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

28
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

29
Runtime Configuration Scripts (continued)

Figure 8-11 The Linux initialization process
30
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

31
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

32
The X Windows System Linux GUI Components
Figure 8-15 Components of the Linux GUI
33
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

34
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

35
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

36
Windows Managers and Desktop Environments
(continued)
Figure 8-16 The KDE desktop environment
37
Windows Managers and Desktop Environments
(continued)
Figure 8-17 The GNOME desktop environment
38
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

39
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

40
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

41
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

42
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

43
Configuring X Windows (continued)
Figure 8-21 Selecting a keyboard layout
44
Configuring X Windows (continued)
Figure 8-22 The Display Settings utility
45
Configuring X Windows (continued)
Figure 8-23 Configuring video card and monitor
model
46
Configuring X Windows (continued)
Figure 8-24 Configuring dual display support
47
Configuring X Windows (continued)
Figure 8-25 The xvidtune utility
48
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

49
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

50
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