Transcript
Page 1: Linux+ Guide to Linux Certification, Third Edition Chapter 11 Compression, System Backup, and Software Installation

Linux+ Guide to Linux Certification, Third Edition

Chapter 11Compression, System Backup,

and Software Installation

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Objectives

• Outline the features of common compression utilities

• Compress and decompress files using common compression utilities

• Perform system backups using the tar, cpio, and dump commands

• View and extract archives using the tar, cpio, and restore commands

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Objectives (continued)

• Use burning software to back up files to CD and DVD

• Describe common types of Linux software

• Compile and install software packages from source code

• Use the Red Hat Package Manager to install, manage, and remove software packages

• Use the yum command to obtain software from Internet software repositories

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Compression

• Compression: process in which files are reduced in size by stripping out characters

• Compression algorithm: standard set of instructions used to compress a file

• Compression ratio: percentage by which the file size was decreased

• Common compression utilities include compress, gzip, and bzip2

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The compress Utility

• Use to compress files using the Adaptive Lempel Ziv coding (LZW) compression algorithm– Average compression ratio of 40-50%

• compress command: used to compress files• zcat command: used to display the contents of an

archive created with compress– Can use zmore and zless commands to view

contents page-by-page

• uncompress command: used to decompress files compressed by compress command

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The compress Utility (continued)

Table 11-1: Common options used with the compress utility

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The gzip Utility

• GNU zip (gzip): used to compress files using the Lempel-Ziv compression algorithm (LZ77)– Varies slightly from algorithm used by compress– Average compression ratio of 60-70%– Uses .gz filename extension by default– Can control level of compression via numeric option

• gunzip command: used to decompress .gz files

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The gzip Utility (continued)

Table 11-2: Common options used with the gzip utility

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The gzip Utility (continued)

Table 11-2 (continued): Common options used with the gzip utility

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The gzip Utility (continued)

Table 11-2 (continued): Common options used with the gzip utility

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The bzip2 Utility

• bzip2 command: used to compress files using Burrows-Wheeler Block Sorting Huffman Coding compression algorithm– Cannot compress directory full of files– Cannot use zcat and zmore to view files

• Must use bzcat command

– Compression ratio is 50% to 75% on average– Uses .bz2 filename extension by default

• bunzip2 command: used to decompress files compressed via bzip2

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The bzip2 Utility (continued)

Table 11-3: Common options used with the bzip2 utility

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The bzip2 Utility (continued)

Table 11-3 (continued): Common options used with the bzip2 utility

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System Backup

• System backup: process whereby files are copied to an archive

• Archive: location (file or device) that contains copy of files– Typically created by a backup utility

• Should backup user files from home directories and any important system configuration files– Possibly files used by system services as well

• Several backup utilities available– tar, cpio, dump/restore, burning software

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System Backup (continued)

Table 11-4: Common tape device files

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The tar Utility

• Tape archive (tar) utility: one of oldest and most common backup utilities– Can create archive in a file on a filesystem or directly

on a device

• tar command: activates tar utility– Arguments list the files to place in the archive– Accepts options to determine location of archive and

action to perform on archive

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The tar Utility (continued)

Table 11-5: Common options used with the tar utility

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The tar Utility (continued)

Table 11-5 (continued): Common options used with the tar utility

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The tar Utility (continued)

• tar utility does not compress files inside archive– Time needed to transfer archive across a network is

high– Can compress archive

• Backing up files to compressed archive on a filesystem is useful when transferring data across a network– Use options of the tar command to compress an

archive immediately after creation

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The cpio Utility

• Copy in/out (cpio): common backup utility– Activated by the cpio command

• Has various options

– Includes options similar to tar utility– Has added features

• Ability to back up device files

• Long filenames

– Uses absolute pathnames by default when archiving

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The cpio Utility (continued)

Table 11-6: Common options used with the cpio command

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The cpio Utility (continued)

Table 11-6 (continued): Common options used with the cpio command

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The dump/restore Utility

• dump/restore: Used to back up files and directories to device or file on filesystem– Works only with files on ext2 and ext3 filesystems

• Designed to backup entire filesystems to an archive

• /etc/dumpdates: file used to store information about incremental and full backups

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The dump/restore Utility (continued)

• Full backup: archiving all data on filesystem

• Incremental backup: backs up only data that has changed since last backup– Can perform up to nine different incremental

backups

• dump command: create archives for full or incremental backup

• restore command: extract archives created with dump

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The dump/restore Utility (continued)

Figure 11-1: A sample back-up strategy

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The dump/restore Utility (continued)

Table 11-7: Common options used with the dump/restore utility

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Burning Software

• tar, cpio, and dump utilities copy data to backup medium in character-by-character or block-by-block format– Typically used with tape, floppy, and hard disk media

• Disc burning software: used to write files to CD or DVD media– Build CD or DVD filesystem, organize the data, and

write it all to CD or DVD

• Fedora 13 comes with Brasero Disc Burner burning software

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Burning Software (continued)

Figure 11-2: The Brasero Disc Burner program

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Software Installation

• Software for Linux can consist of: – Binary files precompiled to run on certain hardware

architectures – Source code, which must be compiled before use

• Typically distributed in tarball format

• Package manager: system that defines standard package format – Used to install, query, and remove packages

• Red Hat Package Manager (RPM): most common package manager used by Linux systems today

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Compiling Source Code into Programs

• Procedure for compiling source code into binary programs standardized among most OSS developers

• make command: looks for Makefile and it to compile the source code into binary using compiler– Makefile: contains most of the information and

commands necessary to compile a program, as well as instructions for use of commented areas

• make install command: copies complied executable programs to correct location

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Compiling Source Code into Programs (continued)

Figure 11-3: The rdesktop program

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Installing Programs Using RPM

• Packages in RPM format have filenames that indicate hardware architecture for which the software was compiled– End with .rpm extension

• To install an RPM package, use –i option to rpm command– Command used to install, query, and remove RPM

packages

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Installing Programs Using RPM (continued)

• After installation RPM database is updated to contain information about the installed package and files contained in it-q option: query the full package name

-i option: together with –q used to display full package information

-f option: together with –q used to display the package to which a specific file belongs

-e option: used to remove a package from the system

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Installing Programs Using RPM (continued)

Figure 11-4: The bluefish program

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Installing Programs Using RPM (continued)

Table 11-8: Common options used with the rpm utility

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Installing Programs Using RPM (continued)

Table 11-8 (continued): Common options used with the rpm utility

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Installing Programs Using RPM (continued)

• Most RPM packages are located on Internet Servers– Called software repositories

• yum command: used to search Internet software repositories for RPM packages– Installs dependent packages if necessary– yum install packagename command– yum update packagename command– KPackageKit: graphical utility for installing or

updating packages

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Installing Programs Using RPM (continued)

Figure 11-5: The KPackageKit utility

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Summary

• Many compression utilities are available for Linux systems; each uses a different compression algorithm and produces a different compression ratio

• Files can be backed up to an archive using a backup utility– To back up files to CD-RW or DVD-RW, use burning

software instead of a backup utility

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Summary (continued)

• tar is the most common backup utility used today– Typically used to create compressed archives called

tarballs

• Source code for Linux software can be obtained and compiled afterward using the GNU C Compiler– Most source code is available in tarball format via

the Internet

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Summary (continued)

• Package Managers install and manage compiled software of the same format– The Red Hat Package Manager is the most common

package manager available for Linux systems today

• You can install or upgrade RPM packages using the yum command– yum command obtains RPM packages from software

repositories on the Internet


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