linux+ guide to linux certification, third edition
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Week 8 System Initialization and X Windows. Linux+ Guide to Linux Certification, Third Edition. Objectives. Summarize the major steps necessary to boot a Linux system Configure the LILO and GRUB boot loaders - PowerPoint PPT PresentationTRANSCRIPT
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
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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 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
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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
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The Boot Process (continued)
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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)
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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
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GRUB (continued)
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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
Linux+ Guide to Linux Certification, 3e 10
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
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GRUB (continued)
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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
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LILO (continued)
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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
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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
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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
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Using GRUB or LILO to Dual Boot Other Operating Systems (continued)
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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
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Using a Windows Boot Loader to Dual Boot Linux (continued)
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Figure 8-9: The EasyBCD program
Using a Windows Boot Loader to Dual Boot Linux (continued)
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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
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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
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Runlevels (continued)
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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
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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
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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
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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
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Runtime Configuration Scripts (continued)
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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
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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
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The X Windows System: Linux GUI Components
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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
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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
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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
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Windows Managers and Desktop Environments (continued)
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Figure 8-16: The KDE desktop environment
Windows Managers and Desktop Environments (continued)
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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
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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
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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
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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
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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 (continued)
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Figure 8-21: Selecting a keyboard layout
Configuring X Windows (continued)
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Figure 8-22: The Display Settings utility
Configuring X Windows (continued)
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Figure 8-23: Configuring video card and monitor model
Configuring X Windows (continued)
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Figure 8-24: Configuring dual display support
Configuring X Windows (continued)
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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
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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 (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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