Chapter 4
Running a Linux System
Guide to Linux Installation and Administration
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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
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Valued Gateway
Client:
Working with Linux Files and
Directories
• 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
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Standard Linux Subdirectories of the
Root Directory
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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
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A Command-Line Window in a
Graphical Environment
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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
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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
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Commands for Managing
Files and Directories
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Commands for Managing
Files and Directories
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Managing Files with Command-Line
Utilities
• Filenames
– Are case-sensitive
– Can be up to 256 characters
– Can include file extensions
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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
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The Nautilus File Manager Window
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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
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The Properties Dialog Box
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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
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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
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Commonly Used File Permission
Settings
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The Permissions Tab of the Properties
Dialog Box
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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
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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
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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
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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
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The Main Window of the
GnoRPM Utility
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Using kPackage to Display Software
Package Information
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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
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Compression Utilities in Linux
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The Linux Kernel
• Each Linux kernel has:
– Release number
– Timestamp
– Modules
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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
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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
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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
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Locating Modules
• The module files are stored in
/lib/modules/version/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
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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
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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
system’s hardware
• You can add boot parameters at the boot
manager selection prompt
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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
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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
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Reviewing Run Level Services
• A run level is a mode of operation in which a
preconfigured set of services is activated
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The Linux Initialization Process
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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
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The Service Configuration Utility
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The ksysv Graphical Services
Configuration Utility
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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
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Shutting Down Linux
• You can shut down Linux by:
–
–
–
–
–
The reboot command
The halt command
The shutdown command
Pressing Ctrl+Alt+Del
The telinit 0 command
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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
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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
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