Linux Guide to Linux Certification

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					Linux+ Guide to Linux
     Certification

        Chapter 12
Compression, 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, 2e            2
            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




    Linux+ Guide to Linux Certification, 2e      3
                     Compression

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

    Linux+ Guide to Linux Certification, 2e       4
              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




    Linux+ Guide to Linux Certification, 2e       5
  The compress Utility (continued)




Table 12-1: Common options used with the compress utility


   Linux+ Guide to Linux Certification, 2e              6
                      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



       Linux+ Guide to Linux Certification, 2e             7
    The gzip Utility (continued)




Table 12-2: Common options used with the gzip utility

Linux+ Guide to Linux Certification, 2e                 8
          The gzip Utility (continued)




Table 12-2 (continued): Common options used with the gzip utility

      Linux+ Guide to Linux Certification, 2e                9
          The gzip Utility (continued)




Table 12-2 (continued): Common options used with the gzip utility

      Linux+ Guide to Linux Certification, 2e               10
                  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

    Linux+ Guide to Linux Certification, 2e      11
    The bzip2 Utility (continued)




Table 12-3: Common options used with the bzip2 utility

 Linux+ Guide to Linux Certification, 2e                 12
          The bzip2 Utility (continued)




Table 12-3 (continued): Common options used with the bzip2 utility

      Linux+ Guide to Linux Certification, 2e                13
                   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

    Linux+ Guide to Linux Certification, 2e            14
    System Backup (continued)




        Table 12-4: Common tape device files



Linux+ Guide to Linux Certification, 2e        15
                     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




    Linux+ Guide to Linux Certification, 2e              16
      The tar Utility (continued)




Table 12-5: Common options used with the tar utility

Linux+ Guide to Linux Certification, 2e                17
           The tar Utility (continued)




Table 12-5 (continued): Common options used with the tar utility
     Linux+ Guide to Linux Certification, 2e                18
          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


    Linux+ Guide to Linux Certification, 2e               19
                   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




    Linux+ Guide to Linux Certification, 2e        20
    The cpio Utility (continued)




Table 12-6: Common options used with the cpio utility

Linux+ Guide to Linux Certification, 2e                 21
          The cpio Utility (continued)




Table 12-6 (continued): Common options used with the cpio utility

      Linux+ Guide to Linux Certification, 2e               22
           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




    Linux+ Guide to Linux Certification, 2e          23
  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




    Linux+ Guide to Linux Certification, 2e     24
The dump/restore Utility (continued)




        Figure 12-1: A sample backup strategy

 Linux+ Guide to Linux Certification, 2e        25
 The dump/restore Utility (continued)




Table 12-7: Common options used with the dump/restore utility
    Linux+ Guide to Linux Certification, 2e               26
                 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




    Linux+ Guide to Linux Certification, 2e           27
  Burning Software (continued)




       Figure 12-2: The X-CD-Roast program

Linux+ Guide to Linux Certification, 2e      28
              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

    Linux+ Guide to Linux Certification, 2e           29
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

    Linux+ Guide to Linux Certification, 2e          30
Compiling Source Code into Programs
            (continued)




           Figure 12-3: The rdesktop program
  Linux+ Guide to Linux Certification, 2e      31
     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



    Linux+ Guide to Linux Certification, 2e         32
Installing Programs Using RPM
           (continued)




          Figure 12-4: The bluefish program
Linux+ Guide to Linux Certification, 2e       33
Installing Programs Using RPM
           (continued)




Table 12-8: Common options used with the rpm utility
Linux+ Guide to Linux Certification, 2e                34
      Installing Programs Using RPM
                 (continued)




Table 12-8 (continued): Common options used with the rpm utility
      Linux+ Guide to Linux Certification, 2e              35
Installing Programs Using RPM
           (continued)




        Figure 12-5: Configuring Fedora core
         software packages after installation
Linux+ Guide to Linux Certification, 2e         36
                        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

    Linux+ Guide to Linux Certification, 2e        37
             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




    Linux+ Guide to Linux Certification, 2e                38
             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




    Linux+ Guide to Linux Certification, 2e   39

				
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