SUSE Linux Enterprise Server Administration Course 3037

1. SUSE Linux Enterprise Server Administration (Course 3037) Chapter 5 Manage System Initialization

2. SUSE Linux Enterprise Server Administration (Course 3037) 2 Objectives Describe the Linux Load Procedure Manage Runlevels Manage the Kernel Manage the GRUB Boot Loader Modify System Settings

3. SUSE Linux Enterprise Server Administration (Course 3037) 3 Describe the Linux Load Procedure Objectives BIOS and Boot Manager Kernel initrd and linuxrc init

4. SUSE Linux Enterprise Server Administration (Course 3037) 4 Describe the Linux Load Procedure (continued)

5. SUSE Linux Enterprise Server Administration (Course 3037) 5 Describe the Linux Load Procedure (continued) BIOS and Boot Manager Tasks performed by the BIOS Power-on self-test Initial detection and setup of hardware Accessing bootable devices BIOS also reads the MBR (Master Boot Record) BIOS starts the boot manager Using the code in the MBR Boot manager (such as GRUB) Loads the kernel and the initrd to memory and starts the kernel

6. SUSE Linux Enterprise Server Administration (Course 3037) 6 Describe the Linux Load Procedure (continued) Kernel Uncompresses itself Organizes and takes control of the continued booting of the system Checks and sets the console Reads BIOS settings Initializes basic hardware interfaces Probes existing hardware and initialize it accordingly Manages hardware access Allocates CPU time and memory to programs

7. SUSE Linux Enterprise Server Administration (Course 3037) 7 Describe the Linux Load Procedure (continued) initrd and linuxrc Boot manager informs the kernel that an initrd exists And where it is located in memory If initrd exists, it is integrated into the kernel Kernel decompresses the initrd And mounts it as a temporary root file system linuxrc Loads modules required to mount root file system May be dynamically linked As soon as linuxrc finishes initrd is unmounted and the boot process continues

8. SUSE Linux Enterprise Server Administration (Course 3037) 8 Describe the Linux Load Procedure (continued) init Boots the system with all its programs and configurations init process has ID number of 1 /etc/inittab file Configuration file /etc/init.d/boot script Controls the start of services /etc/init.d/rc script Uses configured runlevels to start services and daemons

9. SUSE Linux Enterprise Server Administration (Course 3037) 9 Manage Runlevels Objectives Runlevel Basics How to Change the Runlevel at Boot How to Manage Runlevels from the Command Line How to Shut Down or Halt the System How to Set Runlevels with YaST

10. SUSE Linux Enterprise Server Administration (Course 3037) 10 Runlevel Basics What runlevels are Various runlevels define the state of the system init configuration file (/etc/inittab) Determines what happens on individual runlevels Syntax: id:rl:action:process Standard entries parameters initdefault bootwait wait ctrlaltdel respwan

11. SUSE Linux Enterprise Server Administration (Course 3037) 11 Runlevel Basics (continued)

12. SUSE Linux Enterprise Server Administration (Course 3037) 12 Runlevel Basics (continued) init scripts Located in the directory /etc/init.d/ Scripts can be called up Directly by init when you boot the system Indirectly by init when you change the runlevel Directly by the /etc/init.d/ script start or stop commands Some of the most important script include boot boot.local boot.setup halt rc

13. SUSE Linux Enterprise Server Administration (Course 3037) 13 Runlevel Basics (continued)

14. SUSE Linux Enterprise Server Administration (Course 3037) 14 Runlevel Basics (continued)

15. SUSE Linux Enterprise Server Administration (Course 3037) 15 Runlevel Basics (continued) Runlevel symbolic links Each runlevel has a subdirectory in /etc/init.d/ Types of files Sxxservice Kxxservice Point to service scripts in /etc/init.d/ Some links point to the same script

16. SUSE Linux Enterprise Server Administration (Course 3037) 16 Runlevel Basics (continued)

17. SUSE Linux Enterprise Server Administration (Course 3037) 17 Runlevel Basics (continued)

18. SUSE Linux Enterprise Server Administration (Course 3037) 18 Runlevel Basics (continued)

19. SUSE Linux Enterprise Server Administration (Course 3037) 19 Runlevel Basics (continued) How init determines which services to start and stop Script /etc/init.d/rc examines directories /etc/init.d/rccurrentrl.d/ and /etc/init.d/rcnewrl.d Options Kxx link in /etc/init.d/rccurrentrl.d/ and Sxx link in /etc/init.d/rcnewrl.d/ for the same service Script in /etc/init.d/ is not called at all Kxx link in /etc/init.d/rccurrentrl.d/ and no Sxx link in /etc/init.d/rcnewrl.d/ Stop script in /etc/init.d/service Sxx link in /etc/init.d/rcnewrl.d/ and no Kxx link in /etc/init.d/rccurrentrl.d/ Start script in /etc/init.d/service

20. SUSE Linux Enterprise Server Administration (Course 3037) 20 Runlevel Basics (continued) Activate and deactivate services for a runlevel Use command insserv or YaST INIT INFO block at the beginning of script Determines in which runlevel the service should start or stop Used by insserv Use insserv after editing the INIT INFO block To create the needed links and renumber the existing ones as needed Use /etc/init.d/service stop, and then insserv -r service To remove all links for a service

21. SUSE Linux Enterprise Server Administration (Course 3037) 21 How to Change the Runlevel at Boot The standard runlevel is 3 or 5 GRUP choices Linux Floppy Failsafe Entry Linux options root vga runlevel Example: root=/dev/hda4 vga=791 1

22. SUSE Linux Enterprise Server Administration (Course 3037) 22 How to Manage Runlevels from the Command Line Change to another runlevel Using command init Stop the system Entering init 0 Restart the system Entering init 6 Ctrl + Alt + Backspace Restarts the X Window system Restart graphical system Enter init 5

23. SUSE Linux Enterprise Server Administration (Course 3037) 23 How to Shut Down or Halt the System System should always be shut down properly Command shutdown Controls the shutdown of the system Informs all users that the system will be shut down Does not allow other users to log in before it shuts down

24. SUSE Linux Enterprise Server Administration (Course 3037) 24 How to Shut Down or Halt the System (continued)

25. SUSE Linux Enterprise Server Administration (Course 3037) 25 How to Set Runlevels with YaST Steps Start YaST Runlevel Editor module Switch to the Expert mode Select a new default runlevel (optional) Select a service and runlevels associated with it Select Start Now, Stop Now, or Refresh status (optional) Enable, disable the service

26. SUSE Linux Enterprise Server Administration (Course 3037) 26 How to Set Runlevels with YaST (continued)

27. SUSE Linux Enterprise Server Administration (Course 3037) 27 How to Set Runlevels with YaST (continued)

28. SUSE Linux Enterprise Server Administration (Course 3037) 28 Exercise 5-1 Manage Run Levels In this exercise you will manage run levels

29. SUSE Linux Enterprise Server Administration (Course 3037) 29 Manage the Kernel Objectives Kernel Module Basics How to Find Hardware Driver Information How to Manage Modules from the Command Line modprobe Configuration File (/etc/modprobe.conf) Kernel Module Loader (kmod)

30. SUSE Linux Enterprise Server Administration (Course 3037) 30 Kernel Module Basics Kernel is installed in directory /boot/ Drivers can be compiled into the kernel Or be loaded as kernel modules Kernel modules are in lib/modules/version/kernel/ Files and directories related to the kernel /boot/initrd /boot/vmlinuz /proc/sys/kernel/ /proc/version /usr/src/linux/

31. SUSE Linux Enterprise Server Administration (Course 3037) 31 How to Find Hardware Driver Information Command hwinfo Detects the hardware of your system Selects the drivers needed to run this hardware Syntax hwinfo --hardware_type hwinfo --help (for a short introduction to the command)

32. SUSE Linux Enterprise Server Administration (Course 3037) 32 Exercise 5-2 View Information about the Hardware System In this exercise, you do the following: Part I: View General Information about the Hardware System Part II: View Information about Specific Hardware

33. SUSE Linux Enterprise Server Administration (Course 3037) 33 How to Manage Modules from the Command Line lsmod Lists the currently loaded modules in the kernel insmod module Loads the indicated module into the kernel rmmod module Removes the indicated module from the kernel modprobe module Loads the indicated module into the kernel Or removes it (with option -r)

34. SUSE Linux Enterprise Server Administration (Course 3037) 34 How to Manage Modules from the Command Line (continued) depmod Creates the file /lib/modules/version/modules.dep modinfo option module Displays information about the module indicated

35. SUSE Linux Enterprise Server Administration (Course 3037) 35 modprobe Configuration File (/etc/modprobe.conf) /etc/modprobe.conf Configuration file for the kernel modules Command types install Lets modprobe execute commands when loading a specific module into the kernel alias Determine which kernel module will be loaded for a specific device file options Options for loading a module

36. SUSE Linux Enterprise Server Administration (Course 3037) 36 Kernel Module Loader (kmod) kmod Most elegant way to use modules Performs background monitoring Makes sure modules are loaded by modprobe Activate kmod Option Kernel module loader needs to be set to “y” (yes) In the kernel configuration kmod is not designed to unload modules automatically

37. SUSE Linux Enterprise Server Administration (Course 3037) 37 Exercise 5-3 Manage the Linux Kernel In this exercise, you view information about your kernel, and load and unload kernel modules

38. SUSE Linux Enterprise Server Administration (Course 3037) 38 Manage the GRUB Boot Loader Objectives What a Boot Manager Is Boot Managers in SUSE Linux How to Start the GRUB Shell How to Modify the GRUB Configuration File How to Configure GRUB with YaST

39. SUSE Linux Enterprise Server Administration (Course 3037) 39 What a Boot Manager Is Boot loader Loads the operating system kernel Which then loads the system Locates the operating system files on the hard drive And starts the operating system Boot manager Can handle several operating systems Two-stage architecture Stage 1: contains code to load stage 2 Stage 2: contains the actual boot manager

40. SUSE Linux Enterprise Server Administration (Course 3037) 40 Boot Managers in SUSE Linux GRUB Boot Manager Standard boot manager in SLES GRUB features include File system support Interactive control LILO Boot Manager Configuration file is /etc/lilo.conf Structure similar to GRUB configuration file

41. SUSE Linux Enterprise Server Administration (Course 3037) 41 Boot Managers in SUSE Linux (continued) Map files, GRUB, and LILO Kernel is a file within a file system on a partition Concepts unknown to the BIOS Maps Note physical block numbers on disk that comprise logical files BIOS loads all blocks listed in maps LILO relies entirely on maps GRUB tries to become independent from maps at an early stage

42. SUSE Linux Enterprise Server Administration (Course 3037) 42 Boot Managers in SUSE Linux (continued) Additional information Linux system Manual pages and info file README files In the directory /usr/share/doc/packages/grub/ In the directory /usr/share/doc/packages/lilo/ Internet sites www.gnu.org/software/grub/

43. SUSE Linux Enterprise Server Administration (Course 3037) 43 How to Start the GRUB Shell From a running system Enter command grub as root Command find Finds out which partition contains the kernel Close GRUB shell by entering quit From the boot prompt From the graphical boot selection menu, press Esc A text-based menu appears Start the GRUB shell by typing c

44. SUSE Linux Enterprise Server Administration (Course 3037) 44 How to Modify the GRUB Configuration File Edit file /boot/grub/menu.lst structure File structure General options Options for various operating systems That can be booted with the GRUB

45. SUSE Linux Enterprise Server Administration (Course 3037) 45 How to Configure GRUB with YaST Steps Start YaST Boot Loader Configuration module Add, edit, or delete an option Display and edit the configuration files (optional) Select additional boot options (optional)

46. SUSE Linux Enterprise Server Administration (Course 3037) 46 How to Configure GRUB with YaST (continued)

47. SUSE Linux Enterprise Server Administration (Course 3037) 47 Exercise 5-4 Manage the Boot Loader In this exercise you do the following: Part I: Pass Kernel Parameters to the Boot Loader Part II: Configure Boot Managers

48. SUSE Linux Enterprise Server Administration (Course 3037) 48 Modify System Settings Tasks involved View and Change System Settings (/proc/sys/) Modify Kernel and Hardware Parameters with Powertweak Configure /etc/sysconfig/ Files with YaST

49. SUSE Linux Enterprise Server Administration (Course 3037) 49 View and Change System Settings (/proc/sys/) Files in /proc/ and /proc/sys/ are kept in memory Changes to these files are lost after a reboot View the current configuration Use cat and less to view files in /proc/sys/ Use sysctl to view modifiable values below /proc/sys/ Edit the current configuration Use echo to edit individual configuration values You can also use sysctl Use sysctl to load and set kernel parameters Execute script Activate it by entering insserv –d boot.sysctl

50. SUSE Linux Enterprise Server Administration (Course 3037) 50 Modify Kernel and Hardware Parameters with Powertweak Steps Start YaST Powertweak Configuration module Create the Powertweak configuration file Find a parameter Select or enter the setting Find and configure other setting (optional) Review and save the changes

51. SUSE Linux Enterprise Server Administration (Course 3037) 51 Modify Kernel and Hardware Parameters with Powertweak (continued)

52. SUSE Linux Enterprise Server Administration (Course 3037) 52 Modify Kernel and Hardware Parameters with Powertweak (continued)

53. SUSE Linux Enterprise Server Administration (Course 3037) 53 Modify Kernel and Hardware Parameters with Powertweak (continued)

54. SUSE Linux Enterprise Server Administration (Course 3037) 54 Modify Kernel and Hardware Parameters with Powertweak (continued)

55. SUSE Linux Enterprise Server Administration (Course 3037) 55 Configure /etc/sysconfig/ Files with YaST Changes to system configuration with YaST happen in one of the following ways: Direct modification of configuration files YaST modifies the configuration files in /etc/sysconfig/ Directory /etc/sysconfig/ Saves majority of configuration settings for SLES Edit these files by using YaST modules YaST module /etc/sysconfig Editor

56. SUSE Linux Enterprise Server Administration (Course 3037) 56 Configure /etc/sysconfig/ Files with YaST (continued) Steps Start YaST /etc/sysconfig Editor module Find a setting Select or enter a setting Find and configure other settings Select Confirm Each Activation Command Review and save changes

57. SUSE Linux Enterprise Server Administration (Course 3037) 57 Configure /etc/sysconfig/ Files with YaST (continued)

58. SUSE Linux Enterprise Server Administration (Course 3037) 58 Configure /etc/sysconfig/ Files with YaST (continued)

59. SUSE Linux Enterprise Server Administration (Course 3037) 59 Configure /etc/sysconfig/ Files with YaST (continued)

60. SUSE Linux Enterprise Server Administration (Course 3037) 60 Exercise 5-5 Change the Power Setting with YaST In this exercise you will change the power setting of your SLES system using YaST

61. SUSE Linux Enterprise Server Administration (Course 3037) 61 Summary The boot manager starts the Linux kernel A Linux system is categorized using runlevels init daemon Loads and unloads daemons using its configuration file /etc/inittab /etc/inittab file Runs scripts in the /etc/init.d/rcrunlevel.d View current runlevel Using the runlevel command

62. SUSE Linux Enterprise Server Administration (Course 3037) 62 Summary (continued) Start individual daemons By running script in the /etc/init.d with start argument Or by using the rcdaemonname start command Device drivers are either Compiled into the Linux kernel Loaded into the kernel as modules Linux kernel is loaded into memory during system initialization By a boot loader or boot manager

63. SUSE Linux Enterprise Server Administration (Course 3037) 63 Summary (continued) LILO Traditional Linux boot manager GRUB boot loader Used by default in SLES /etc/lilo.conf file LILO configuration file /proc/sys/ directory Exists in memory Contains information and settings for a running system