Linux Guide to Linux Certification, Third Edition

1
Linux Guide to Linux Certification, Third Edition

• Chapter 11
• Compression, System Backup, and Software
  Installation

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

3
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