Linux Guide to Linux Certification

1
Linux Guide to Linux Certification

• Chapter 12
• 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

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Objectives (continued)

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

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Compression

• Compression Process in which files are reduced
  in size by a compression algorithm
• Compression algorithm Set of instructions used
  to systematically reduce a files contents
• Compression ratio Amount of compression
  occurring during compression
• Three most common compression utilities
• Compress
• gzip
• bzip2

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The compress Utility

• compress command Used to compress files using
  Lempel-Ziv compression algorithm
• zcat command Used to view contents of an archive
  created with compress or gzip to Standard Output
• uncompress command Used to decompress files
  compressed by compress command

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The compress Utility (continued)
Table 12-1 Common options used with the compress
utility
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The gzip Utility

• GNU zip (gzip) Used to compress files using
  Lempel-Ziv compression algorithm
• Varies slightly from algorithm used by compress
• Typically yields better compression than compress
• Uses .gz filename extension by default
• Can control level of compression
• gunzip command Used to decompress .gz files

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The gzip Utility (continued)
Table 12-2 Common options used with the gzip
utility
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The gzip Utility (continued)
Table 12-2 (continued) Common options used with
the gzip utility
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The gzip Utility (continued)
Table 12-2 (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
• bunzip2 command Used to decompress files
  compressed via bzip2

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The bzip2 Utility (continued)
Table 12-3 Common options used with the bzip2
utility
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The bzip2 Utility (continued)
Table 12-3 (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 12-4 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
• Accepts options to determine location of archive
  and action to perform on archive

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The tar Utility (continued)
Table 12-5 Common options used with the tar
utility
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The tar Utility (continued)
Table 12-5 (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
• Ill suited to backing up large amounts of data
  for system recovery

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The cpio Utility

• Copy in/out (cpio) Common backup utility
• 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 12-6 Common options used with the cpio
utility
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The cpio Utility (continued)
Table 12-6 (continued) Common options used with
the cpio utility
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The dump/restore Utility

• dump/restore Used to back up files and
  directories to device or file on filesystem
• Works with files on ext2 and ext3 filesystems
• /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
• restore command Extract archives created with
  dump

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The dump/restore Utility (continued)
Figure 12-1 A sample backup strategy
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The dump/restore Utility (continued)
Table 12-7 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
• Burning software Used to write files to CD-RW or
  DVD-RW media
• Red Hat Fedora Core 2 comes with X-CD-Roast

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Burning Software (continued)
Figure 12-2 The X-CD-Roast 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
• 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
• GNU C Compiler (gcc) Command used to compile
  source code into binary programs
• After compilation, must move program files to
  appropriate directory
• Makefile Contains most of information and
  commands necessary to compile program

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Compiling Source Code into Programs (continued)
Figure 12-3 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)
Figure 12-4 The bluefish program
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Installing Programs Using RPM (continued)
Table 12-8 Common options used with the rpm
utility
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Installing Programs Using RPM (continued)
Table 12-8 (continued) Common options used with
the rpm utility
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Installing Programs Using RPM (continued)
Figure 12-5 Configuring Fedora core software
packages after installation
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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
• Tape devices are the most common medium used for
  archives
• 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
• Creates 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