Week 8 System 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, 3e2

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 Linux+ Guide to Linux Certification, 3e3

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 Linux+ Guide to Linux Certification, 3e4

The Boot Process (continued)  /boot: directory containing kernel and boot-related files  Vmlinuz- : 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 Linux+ Guide to Linux Certification, 3e5

The Boot Process (continued) Linux+ Guide to Linux Certification, 3e6 Figure 8-1: The boot process

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, 3e7

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 Linux+ Guide to Linux Certification, 3e8

GRUB (continued) Linux+ Guide to Linux Certification, 3e9 Figure 8-2: GRUB boot loader screen

GRUB (continued)  To configure, edit /boot/grub/grub.conf Read directly by Stage2 boot loader HDDs and partitions identified by numbers ○ Format: (hd, )  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 Linux+ Guide to Linux Certification, 3e10

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 Linux+ Guide to Linux Certification, 3e11

GRUB (continued) Linux+ Guide to Linux Certification, 3e12 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 POST Allows choice of OS to load at startup  To configure, edit /etc/lilo.conf file Linux+ Guide to Linux Certification, 3e13

LILO (continued) Linux+ Guide to Linux Certification, 3e14 Table 8-1: Common /etc/lilo.conf keywords

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 Linux+ Guide to Linux Certification, 3e15

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 Linux+ Guide to Linux Certification, 3e16

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 Linux+ Guide to Linux Certification, 3e17

Using GRUB or LILO to Dual Boot Other Operating Systems (continued) Linux+ Guide to Linux Certification, 3e18 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 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 Linux+ Guide to Linux Certification, 3e19

Using a Windows Boot Loader to Dual Boot Linux (continued) Linux+ Guide to Linux Certification, 3e20 Figure 8-9: The EasyBCD program

Using a Windows Boot Loader to Dual Boot Linux (continued) Linux+ Guide to Linux Certification, 3e21 Figure 8-10: Booting Linux from a Windows boot loader

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 Linux+ Guide to Linux Certification, 3e22

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 Linux+ Guide to Linux Certification, 3e23

Runlevels (continued) Linux+ Guide to Linux Certification, 3e24 Table 8-3: Linux runlevels

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 Linux+ Guide to Linux Certification, 3e25

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 Linux+ Guide to Linux Certification, 3e26

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 Linux+ Guide to Linux Certification, 3e27

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 Linux+ Guide to Linux Certification, 3e28

Runtime Configuration Scripts (continued) Linux+ Guide to Linux Certification, 3e29 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 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 Linux+ Guide to Linux Certification, 3e30

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 Linux+ Guide to Linux Certification, 3e31

The X Windows System: Linux GUI Components Linux+ Guide to Linux Certification, 3e32 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 results Need not run on same computer as X Windows  XFree86: OSS version of X Windows Originally intended for Intel x86 platform Linux+ Guide to Linux Certification, 3e33

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 Linux+ Guide to Linux Certification, 3e34

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 Linux+ Guide to Linux Certification, 3e35

Windows Managers and Desktop Environments (continued) Linux+ Guide to Linux Certification, 3e36 Figure 8-16: The KDE desktop environment

Windows Managers and Desktop Environments (continued) Linux+ Guide to Linux Certification, 3e37 Figure 8-17: The GNOME desktop environment

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 Linux+ Guide to Linux Certification, 3e38

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 Linux+ Guide to Linux Certification, 3e39

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 Linux+ Guide to Linux Certification, 3e40

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 Linux+ Guide to Linux Certification, 3e41

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 Linux+ Guide to Linux Certification, 3e42

Configuring X Windows (continued) Linux+ Guide to Linux Certification, 3e43 Figure 8-21: Selecting a keyboard layout

Configuring X Windows (continued) Linux+ Guide to Linux Certification, 3e44 Figure 8-22: The Display Settings utility

Configuring X Windows (continued) Linux+ Guide to Linux Certification, 3e45 Figure 8-23: Configuring video card and monitor model

Configuring X Windows (continued) Linux+ Guide to Linux Certification, 3e46 Figure 8-24: Configuring dual display support

Configuring X Windows (continued) Linux+ Guide to Linux Certification, 3e47 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 Linux+ Guide to Linux Certification, 3e48

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 Linux+ Guide to Linux Certification, 3e49

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 Linux+ Guide to Linux Certification, 3e50