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Linux+ Guide to Linux Certification, Third Edition

Chapter 11Compression, System Backup,

and Software Installation

Linux+ Guide to Linux Certification, 3e 2

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


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 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



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 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


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 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


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 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


System Backup (continued)

Table 11-4: Common tape device files


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


The tar Utility (continued)

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



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



• 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


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


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


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


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



Figure 11-1: A sample back-up strategy



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 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


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 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


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 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


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



• 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



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 utility– To 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 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


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