Ch08
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Ch08 Presentation Transcript

  • 1. Week 8System Initializationand 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 Linux+ Guide to Linux Certification, 3e 2
  • 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 Linux+ Guide to Linux Certification, 3e 3
  • 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 Linux+ Guide to Linux Certification, 3e 4
  • 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 Linux+ Guide to Linux Certification, 3e 5
  • 6. The Boot Process (continued) Figure 8-1: The boot process Linux+ Guide to Linux Certification, 3e 6
  • 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) Linux+ Guide to Linux Certification, 3e 7
  • 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 Linux+ Guide to Linux Certification, 3e 8
  • 9. GRUB (continued) Figure 8-2: GRUB boot loader screen Linux+ Guide to Linux Certification, 3e 9
  • 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 Linux+ Guide to Linux Certification, 3e 10
  • 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 Linux+ Guide to Linux Certification, 3e 11
  • 12. GRUB (continued) Figure 8-5: Viewing help at the GRUB prompt Linux+ Guide to Linux Certification, 3e 12
  • 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 Linux+ Guide to Linux Certification, 3e 13
  • 14. LILO (continued) Table 8-1: Common /etc/lilo.conf keywords Linux+ Guide to Linux Certification, 3e 14
  • 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 Linux+ Guide to Linux Certification, 3e 15
  • 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 Linux+ Guide to Linux Certification, 3e 16
  • 17. Using GRUB or LILO to Dual BootOther 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, 3e 17
  • 18. Using GRUB or LILO to Dual BootOther Operating Systems(continued) Figure 8-7: Configuring GRUB for a dual boot system Linux+ Guide to Linux Certification, 3e 18
  • 19. Using a Windows Boot Loader toDual 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:NSTmenu.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, 3e 19
  • 20. Using a Windows Boot Loader toDual Boot Linux (continued) Figure 8-9: The EasyBCD program Linux+ Guide to Linux Certification, 3e 20
  • 21. Using a Windows Boot Loader toDual Boot Linux (continued) Figure 8-10: Booting Linux from a Windows boot loader Linux+ Guide to Linux Certification, 3e 21
  • 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 Linux+ Guide to Linux Certification, 3e 22
  • 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 Linux+ Guide to Linux Certification, 3e 23
  • 24. Runlevels (continued) Table 8-3: Linux runlevels Linux+ Guide to Linux Certification, 3e 24
  • 25. 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, 3e 25
  • 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 Linux+ Guide to Linux Certification, 3e 26
  • 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 Linux+ Guide to Linux Certification, 3e 27
  • 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 Linux+ Guide to Linux Certification, 3e 28
  • 29. Runtime Configuration Scripts(continued) Figure 8-11: The Linux initialization process Linux+ Guide to Linux Certification, 3e 29
  • 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 Linux+ Guide to Linux Certification, 3e 30
  • 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 Linux+ Guide to Linux Certification, 3e 31
  • 32. The X Windows System: Linux GUIComponents Figure 8-15: Components of the Linux GUI Linux+ Guide to Linux Certification, 3e 32
  • 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 Linux+ Guide to Linux Certification, 3e 33
  • 34. Windows Managers and DesktopEnvironments 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, 3e 34
  • 35. Windows Managers and DesktopEnvironments (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, 3e 35
  • 36. Windows Managers and DesktopEnvironments (continued) Figure 8-16: The KDE desktop environment Linux+ Guide to Linux Certification, 3e 36
  • 37. Windows Managers and DesktopEnvironments (continued) Figure 8-17: The GNOME desktop environment Linux+ Guide to Linux Certification, 3e 37
  • 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 Linux+ Guide to Linux Certification, 3e 38
  • 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 Linux+ Guide to Linux Certification, 3e 39
  • 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 Linux+ Guide to Linux Certification, 3e 40
  • 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 Linux+ Guide to Linux Certification, 3e 41
  • 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 Linux+ Guide to Linux Certification, 3e 42
  • 43. Configuring X Windows(continued) Figure 8-21: Selecting a keyboard layout Linux+ Guide to Linux Certification, 3e 43
  • 44. Configuring X Windows(continued) Figure 8-22: The Display Settings utility Linux+ Guide to Linux Certification, 3e 44
  • 45. Configuring X Windows(continued) Figure 8-23: Configuring video card and monitor model Linux+ Guide to Linux Certification, 3e 45
  • 46. Configuring X Windows(continued) Figure 8-24: Configuring dual display support Linux+ Guide to Linux Certification, 3e 46
  • 47. Configuring X Windows(continued) Figure 8-25: The xvidtune utility Linux+ Guide to Linux Certification, 3e 47
  • 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 Linux+ Guide to Linux Certification, 3e 48
  • 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 Linux+ Guide to Linux Certification, 3e 49
  • 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 Linux+ Guide to Linux Certification, 3e 50