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 Linux+ Guide to Linux Certification, 3e2

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 Linux+ Guide to Linux Certification, 3e3

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 Linux+ Guide to Linux Certification, 3e4

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 Linux+ Guide to Linux Certification, 3e5

The compress Utility (continued) Linux+ Guide to Linux Certification, 3e6 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 Linux+ Guide to Linux Certification, 3e7

The gzip Utility (continued) Linux+ Guide to Linux Certification, 3e8 Table 11-2: Common options used with the gzip utility

The gzip Utility (continued) Linux+ Guide to Linux Certification, 3e9 Table 11-2 (continued): Common options used with the gzip utility

The gzip Utility (continued) Linux+ Guide to Linux Certification, 3e10 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 Linux+ Guide to Linux Certification, 3e11

The bzip2 Utility (continued) Linux+ Guide to Linux Certification, 3e12 Table 11-3: Common options used with the bzip2 utility

The bzip2 Utility (continued) Linux+ Guide to Linux Certification, 3e13 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 Linux+ Guide to Linux Certification, 3e14

System Backup (continued) Linux+ Guide to Linux Certification, 3e15 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 Linux+ Guide to Linux Certification, 3e16

The tar Utility (continued) Linux+ Guide to Linux Certification, 3e17 Table 11-5: Common options used with the tar utility

The tar Utility (continued) Linux+ Guide to Linux Certification, 3e18 Table 11-5 (continued): Common options used with the tar utility -xExtract Archive -cCreate New Archive -rAppend to Archive -v verbose -fWrite/Read File -tList Archive Contents -zCompress using gzip (c mode only)

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 Linux+ Guide to Linux Certification, 3e19

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 Linux+ Guide to Linux Certification, 3e20

The cpio Utility (continued) Linux+ Guide to Linux Certification, 3e21 Table 11-6: Common options used with the cpio command

The cpio Utility (continued) Linux+ Guide to Linux Certification, 3e22 Table 11-6 (continued): Common options used with the cpio command -iExtract contents to disk -ooutput -ppass-through. Read list of files and copy to specified directory -ZCompress -zgzip -u Unconditional Write -d Create directories as necessary -O fileWrite archive to file -t read contents to standard out -ybzip2

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 Linux+ Guide to Linux Certification, 3e23

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 Linux+ Guide to Linux Certification, 3e24

The dump/restore Utility (continued) Linux+ Guide to Linux Certification, 3e25 Figure 11-1: A sample back-up strategy

The dump/restore Utility (continued) Linux+ Guide to Linux Certification, 3e26 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 Linux+ Guide to Linux Certification, 3e27

Burning Software (continued) Linux+ Guide to Linux Certification, 3e28 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 Linux+ Guide to Linux Certification, 3e29

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 Linux+ Guide to Linux Certification, 3e30

Compiling Source Code into Programs (continued) Linux+ Guide to Linux Certification, 3e31 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 Linux+ Guide to Linux Certification, 3e32

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 Linux+ Guide to Linux Certification, 3e33

Installing Programs Using RPM (continued) Linux+ Guide to Linux Certification, 3e34 Figure 11-4: The bluefish program

Installing Programs Using RPM (continued) Linux+ Guide to Linux Certification, 3e35 Table 11-8: Common options used with the rpm utility

Installing Programs Using RPM (continued) Linux+ Guide to Linux Certification, 3e36 Table 11-8 (continued): Common options used with the rpm utility

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 Linux+ Guide to Linux Certification, 3e37

Installing Programs Using RPM (continued) Linux+ Guide to Linux Certification, 3e38 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 Linux+ Guide to Linux Certification, 3e39

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 Linux+ Guide to Linux Certification, 3e40

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 Linux+ Guide to Linux Certification, 3e41