Running a Linux System

1
Chapter 4

• Running a Linux System

2
Objectives

• In this chapter, you will
• Manage files and directories on a Linux system
  using basic commands
• Launch programs and manage corresponding software
  packages
• Add and remove features from the Linux kernel
• Review and change the initialization process that
  starts a Linux-based computer
• Shut down a Linux system in an orderly way

3
Working with Linux Files and Directories
Valued Gateway Client

• Information in Linux is stored in files organized
  in directories
• Parent directory contains child directories and
  files
• The parent directory for all directories is the
  root directory
• All Linux configuration files are located in
  subdirectories of the root directory

4
Standard Linux Subdirectories of the Root
Directory
5
Working at a Command Line

• Logging in to Linux at a text-mode console
  launches a command-line environment
• Within a graphical environment, you can a
  command-line window by using the xterm program
• The command-line window is also called a terminal
  emulator window

6
A Command-Line Window in a Graphical Environment
7
Managing Files with Command-Line Utilities

• The command-line environment is provided by a
  shell
• Shell program that accepts and acts on the
  commands that you enter
• Absolute path complete description of the
  directory in absolute terms
• Relative path partial description of the
  directory relative to another location

8
Managing Files with Command-Line Utilities

• Linux commands
• are case sensitive
• can include options and parameters
• Information about the date and time when an event
  occurred is stored in the form of a timestamp

9
Commands for Managing Files and Directories
10
Commands for Managing Files and Directories
11
Managing Files with Command-Line Utilities

• Filenames
• Are case-sensitive
• Can be up to 256 characters
• Can include file extensions

12
Managing Files with Graphical Utilities

• Linux desktop includes a file manager
• File manager graphical program to display the
  contents of a directory and manage files and
  directories
• The file manager in Red Hat Linux 7.3 is called
  Nautilus
• To perform basic file management tasks, you can
  drag and drop file icons

13
The Nautilus File Manager Window
14
File Properties

• Each file in Linux has several basic properties
• Type
• Name
• Size
•  Location
• Timestamp
• Each file has the owner of the file, the group
  assigned to the file, and the permissions granted
  to access the file

15
The Properties Dialog Box
16
File Permissions

• File permissions define the access that the owner
  has granted to others on the Linux system
• Types of permissions
• Read permission (r)
• Write permission (w)
• Execute permission (x)
• Permissions can be assigned in three different
  ways
• User permission
• Group permission
• Other permissions

17
File Permissions

• You can alter file ownership and file permissions
  using the chown and chmod commands
• The chmod command uses letters or numeric codes
  to define the file permissions assigned to a file
  or directory
• The umask command determines the file permissions
  assigned when you create a new file

18
Commonly Used File Permission Settings
19
The Permissions Tab of the Properties Dialog Box
20
Running and Managing Software

• Environment variables defined by the Linux shell
  so that all programs can access their values
• Variable memory location used by a program to
  store a value
• The PATH environment variable includes a list of
  all the directories where programs on the system
  are located
• You can display values of the PATH using the echo
  command

21
Function Libraries

• A function is a small task that a computer
  program performs
• A function library is a file that contains
  commonly used functions
• The ldd command lists the libraries that a
  program requires

22
Using rpm to Manage Software Packages

• rpm command
• Manages all of the rpm software packages
• Maintains a database for all the software
  installed on the Linux system
• You can use the rpm command to query the software
  package database or to install or erase software
  packages from the system
• Hundreds of options are supported by the rpm
  command

23
Using Graphical Tools to Manage Software Packages

• GNOME and KDE include graphical programs to
  manage software packages
• The GnoRPM package management utility is included
  with Gnome
• The KDE Desktop includes a package management
  tool called kPackage
• Both GmoRPM and kPackage provide menu items

24
The Main Window of the GnoRPM Utility
25
Using kPackage to Display Software Package
Information
26
Using tar Archive Files

• A tar archive is a collection of many files
  stored in a single file
• The tar command is used to create a tar archive,
  to extract its content, and to create backups of
  files on the system
• A tar archive has a .tar extension
• The resulting file after the tar command with the
  compression options is called a gzipped tarball

27
Compression Utilities in Linux
28
The Linux Kernel

• Each Linux kernel has
• Release number
• Timestamp
• Modules

29
Learning about Your Kernel

• The uname command with the r option displays the
  version of your Linux kernel followed by the
  release number
• A release number is assigned by the company that
  prepared the Linux product
• A timestamp indicates the date and time when the
  kernel was created

30
Kernel Modules

• Linux kernel modules are files containing
  computer code that can be loaded into the kernel
  or removed from the kernel
• Kernel modules can be automatically loaded based
  on the configuration set during the Linux
  installation
• The lsmod command lists the modules that are
  installed in the Linux kernel

31
Adding and Removing Modules

• The modprobe command loads a module with any
  required supporting modules
• The rmmod command removes a module from the
  kernel
• Module parameters provide information needed by
  amodule to locate system resources

32
Locating Modules

• The module files are stored in /lib/modules/versio
  n/kernel directory, where version id the version
  number of the Linux kernel on the system
• This directory contains subdirectories for
  networking-related modules, device drivers, and
  other module types

33
The Initialization Process

• 1. A boot manager loads and starts the Linux
  kernel
• 2. The Linux kernel initializes hardware and then
  launches the init program
• 3. The init program launches a script based on
  the run level in which Linux is to operate
• 4. The script started by init typically runs many
  other scripts to launch and manage system services

34
Booting the Kernel

• GRUB and LILO are the boot managers
• The boot manager displays a prompt listing the
  available operating system to launch
• Boot parameters instruct the Linux kernel how to
  operate or how to access parts of the computer
  systems hardware
• You can add boot parameters at the boot manager
  selection prompt

35
Configuring the Boot Manager

• You can update the configuration of a boot
  manager after the installation is completed
• The configuration file for the LILO boot manager
  is /etc/lilo.conf.anaconda
• The configuration file for GRUB boot manager is
  /boot/grub/grub.conf

36
Initializing System Services

• The init program is a master control program that
  starts other programs and scripts that initialize
  the system services
• A script is a collection of commands that are
  stored in a text file and executed without user
  intervention
• The init program is controlled by the
  /etc/inittab configuration file

37
Reviewing Run Level Services

• A run level is a mode of operation in which a
  preconfigured set of services is activated

38
The Linux Initialization Process
39
Starting and Stopping System Services

• The chconfig program allows you to start and stop
  services when you boot Linux
• RedHat Linux includes a graphical utility to
  configure system services called serviceconf
• The KDE Desktop includes a similar graphical
  utility called ksysv

40
The Service Configuration Utility
41
The ksysv Graphical Services Configuration Utility
42
Configuring System Services

• The initialization scripts in /etc/rc.d/init.d
  are provided when you install Linux
• Configuration details for system services scripts
  are located in the /etc/sysconfig directory and
  its subdirectories

43
Shutting Down Linux

• You can shut down Linux by
• The reboot command
• The halt command
• The shutdown command
• Pressing CtrlAltDel
• The telinit 0 command

44
Summary

• Information in Linux is stored in files organized
  in a directory structure that begins with the
  root directory
• There are basic commands to manage files and
  directories
• Files can be compressed using tar, zip, gzip, and
  other utilities
• Read, Write, and Execute permissions for a file
  or directory can be assigned to the owner, to the
  assigned group, or to all other users on the
  system
• The rpm command is used to query the software
  package database or to install or erase software
  packages from the system

45
Summary

• The Linux kernel supports loadable modules, which
  are managed using the lsmod, insmod, rmmod, and
  modprobe commands
• You can provide boot parameters to the Linux
  kernel at the boot manager selection prompt
• The Linux kernel starts the init program, which
  in turn runs several scripts based on information
  stored in the run level directories
• You can set up which services are activated at
  boot time using the chkconfig command or using
  various graphical utilities
• To avoid data loss, you must gracefully shut down
  Linux using a command such as reboot, halt, or
  shutdown