Linux+ Guide to Linux
Certification, Third Edition
Chapter 11
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
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)
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
The gzip Utility (continued)
The gzip Utility (continued)
The gzip Utility (continued)
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)
The bzip2 Utility (continued)
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
System Backup (continued)
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)
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
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
The cpio Utility (continued)
The cpio Utility (continued)
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
The dump/restore Utility (continued)
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
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)
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
Installing Programs Using RPM
(continued)
Installing Programs Using RPM
(continued)
Installing Programs Using RPM
(continued)
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
Installing Programs Using RPM
(continued)
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
