Chapter 11 Compression, System Backup, and Software Installation

Chapter 11Compression, System Backup, and Software Installation

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

Linux+ Guide to Linux Certification, 3e 2

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


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


The compress Utility Use to compress files using the Adaptive

Lempel Ziv coding (LZW) compression algorithmAverage compression ratio of 40-50%

compress command: used to compress files zcat command: used to display the contents

of an archive created with compressCan use zmore and zless commands to view

contents page-by-page uncompress command: used to decompress

files compressed by compress command


The compress Utility (continued)


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

The gzip Utility GNU zip (gzip): used to compress files

using the Lempel-Ziv compression algorithm (LZ77)Varies slightly from algorithm used by compressAverage compression ratio of 60-70%Uses .gz filename extension by defaultCan control level of compression via numeric

option

gunzip command: used to decompress .gz files


The gzip Utility (continued)


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



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



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

The bzip2 Utility bzip2 command: used to compress files

using Burrows-Wheeler Block Sorting Huffman Coding compression algorithmCannot compress directory full of filesCannot use zcat and zmore to view files

○ Must use bzcat commandCompression ratio is 50% to 75% on averageUses .bz2 filename extension by default

bunzip2 command: used to decompress files compressed via bzip2


The bzip2 Utility (continued)


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

The bzip2 Utility (continued)


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

System Backup System backup: process whereby files are

copied to an archive Archive: location (file or device) that

contains copy of filesTypically created by a backup utility

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

Several backup utilities availabletar, cpio, dump/restore, burning software


System Backup (continued)


Table 11-4: Common tape device files

The tar Utility

Tape archive (tar) utility: one of oldest and most common backup utilitiesCan create archive in a file on a filesystem

or directly on a device

tar command: activates tar utilityArguments list the files to place in the

archiveAccepts options to determine location of

archive and action to perform on archive


The tar Utility (continued)


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

The tar Utility (continued)


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

-x Extract Archive-c Create New Archive-r Append to Archive-v verbose-f Write/Read File-t List Archive Contents-z Compress using gzip (c mode only)

The tar Utility (continued) tar utility does not compress files inside

archiveTime needed to transfer archive across a

network is highCan compress archive

Backing up files to compressed archive on a filesystem is useful when transferring data across a networkUse options of the tar command to compress

an archive immediately after creation


The cpio Utility Copy in/out (cpio): common backup

utilityActivated by the cpio command

○ Has various optionsIncludes options similar to tar utilityHas added features

○ Ability to back up device files ○ Long filenames

Uses absolute pathnames by default when archiving


The cpio Utility (continued)


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

The cpio Utility (continued)


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

-i Extract contents to disk-o output-p pass-through. Read list of files and copy to specified directory-Z Compress-z gzip-u Unconditional Write-d Create directories as necessary-O file Write archive to file-t read contents to standard out-y bzip2

The dump/restore Utility

dump/restore: Used to back up files and directories to device or file on filesystemWorks 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


The dump/restore Utility (continued) Full backup: archiving all data on

filesystem Incremental backup: backs up only data

that has changed since last backupCan perform up to nine different incremental

backups dump command: create archives for full

or incremental backup restore command: extract archives

created with dump


The dump/restore Utility (continued)


Figure 11-1: A sample back-up strategy

The dump/restore Utility (continued)


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

Burning Software tar, cpio, and dump utilities copy data to

backup medium in character-by-character or block-by-block formatTypically used with tape, floppy, and hard disk

media Disc burning software: used to write files to

CD or DVD mediaBuild CD or DVD filesystem, organize the data,

and write it all to CD or DVD Fedora 13 comes with Brasero Disc Burner

burning software


Burning Software (continued)


Figure 11-2: The Brasero Disc Burner program

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


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 compilerMakefile: 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


Compiling Source Code into Programs (continued)


Figure 11-3: The rdesktop program

Installing Programs Using RPM Packages in RPM format have

filenames that indicate hardware architecture for which the software was compiledEnd with .rpm extension

To install an RPM package, use –i option to rpm commandCommand used to install, query, and

remove RPM packages


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




Figure 11-4: The bluefish program



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



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

Installing Programs Using RPM (continued) Most RPM packages are located on

Internet ServersCalled software repositories

yum command: used to search Internet software repositories for RPM packagesInstalls dependent packages if necessaryyum install packagename commandyum update packagename commandKPackageKit: graphical utility for installing or

updating packages




Figure 11-5: The KPackageKit utility

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 utilityTo back up files to CD-RW or DVD-RW, use

burning software instead of a backup utility


Summary (continued)

tar is the most common backup utility used todayTypically used to create compressed

archives called tarballs

Source code for Linux software can be obtained and compiled afterward using the GNU C CompilerMost source code is available in tarball

format via the Internet


Summary (continued)

Package Managers install and manage compiled software of the same formatThe 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 commandyum command obtains RPM packages from

software repositories on the Internet


Documents

Chapter 11 Compression, System Backup, and Software Installation