1. Linux+ Guide to Linux Certification, Third Edition
Chapter 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
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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
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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
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5. 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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6. The Boot Process (continued)
Figure 8-1: The boot process
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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)
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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
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9. Figure 8-2: GRUB boot loader screen
GRUB (continued)
Figure 8-2: GRUB boot loader screen
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10. 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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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 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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12. Figure 8-5: Viewing help at the GRUB prompt
GRUB (continued)
Figure 8-5: Viewing help at the GRUB prompt
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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
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14. Table 8-1: Common /etc/lilo.conf keywords
LILO (continued)
Table 8-1: Common /etc/lilo.conf keywords
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15. Table 8-2: LILO error messages
LILO (continued)
Table 8-2: LILO error messages
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16. 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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17. 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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18. 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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19. 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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20. 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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21. Using a Windows Boot Loader to Dual Boot Linux (continued)
Figure 8-9: The EasyBCD program
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22. Using a Windows Boot Loader to Dual Boot Linux (continued)
Figure 8-10: Booting Linux from a Windows boot loader
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23. 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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24. 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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25. Runlevels (continued)
Table 8-3: Linux runlevels
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26. 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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27. 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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28. 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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29. 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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30. Runtime Configuration Scripts (continued)
Figure 8-11: The Linux initialization process
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31. 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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32. 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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33. The X Windows System: Linux GUI Components
Figure 8-15: Components of the Linux GUI
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34. 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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35. 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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36. 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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37. Windows Managers and Desktop Environments (continued)
Table 8-4: Common window managers
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38. Windows Managers and Desktop Environments (continued)
Figure 8-16: The KDE desktop environment
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39. Windows Managers and Desktop Environments (continued)
Figure 8-17: The GNOME desktop environment
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40. 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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41. 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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42. 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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43. 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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44. 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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45. Configuring X Windows (continued)
Figure 8-21: Selecting a keyboard layout
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46. Configuring X Windows (continued)
Figure 8-22: The Display Settings utility
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47. Configuring X Windows (continued)
Figure 8-23: Configuring video card and monitor model
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48. Configuring X Windows (continued)
Figure 8-24: Configuring dual display support
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49. Configuring X Windows (continued)
Figure 8-25: The xvidtune utility
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50. 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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51. 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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52. 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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