Linux+ Guide to Linux Certification Chapter Thirteen Compression, System Back-Up, and Software Installation

Linux+ Guide to Linux Certification

Chapter Thirteen

Compression, System Back-Up, and Software

Installation

ObjectivesObjectives

• Outline the features of common compression utilities

• Compress and decompress files using common compression utilities

• Perform system back-ups using the tar, cpio, and dump commands

• View and extract archives using the tar, cpio, and restore commands

ObjectivesObjectives

• 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

CompressionCompression

• Compression– Process in which files are reduced in size by a

compression algorithm

• Compression algorithm– Set of instruction used to reduce the contents of a

file systematically

• Compression ratio– Amount of compression that occurred during

compression

CompressionCompression

• The three most common compression utilities available to Linux users:– compress– gzip– bzip2

The compress UtilityThe compress Utility

• compress command– Command used to compress files using a Lempel-

Ziv compression algorithm

• zcat command– Command used to view the contents of an archive

created with compress or gzip to Standard Output


• zmore command– Command used to view the contents of an archive

created with compress or gzip to Standard Output in a page-by-page fashion

• uncompress command– Command used to decompress files compressed

by the compress command


Table 13-1: Common options used with the compress utility

The gzip UtilityThe gzip Utility

• GNU zip (gzip)– Command used to compress files using a Lempel-

Ziv compression algorithm• Varies slightly from the algorithm used by the

compress utility

– Typically, this algorithm yields better compression than the one used by compress


Table 13-2: Common options used with the gzip utility


Table 13-2 (continued): Common options used with the gzip utility

The bzip2 UtilityThe bzip2 Utility

• bzip2 command– Command used to compress files using a

Burrows-Wheeler Block Sorting Huffman Coding compression algorithm

– Cannot be used to compress a directory full of files

– The zcat and zmore commands cannot be used to view files zipped with bzip2

– The compression ratio is 50-75% on average


• bzcat command– Command used to view the contents of an archive

created with bzip2 to Standard Output

• bunzip2 command– Command used to decompress files compressed

by the bzip2 command


Table 13-3: Common options used with the bzip2 utility


Table 13-3 (continued): Common options used with the bzip2 utility

System Back-UpSystem Back-Up

• System back-up– Process whereby files are copied to an archive

• Archive– The location (file or device) that contains a copy

of files– It is typically created by a back-up utility


Table 13-4: Common tape device files


• magnetic tape (mt) command– Command used to control tape devices

• The most common back-up utilities:– tar– cpio– dump/restore

The tar UtilityThe tar Utility

• Tape archive utility– One of the oldest and most common back-up

utilities– Can create an archive in a file on a filesystem or

directly on a device– Accepts options to determine the location of the

archive and the action to perform on the archive


Table 13-5: Common options used with the tar utility


Table 13-5 (continued): Common options used with the tar utility


Table 13-5 (continued): Common options used with the tar utility


• Tarballs– A gzip-compressed tar archive

• Backing up files to a compressed archive on a filesystem is useful when transferring data across a network but is ill-suited to backing up large amounts of data for system recovery

The cpio UtilityThe cpio Utility

• Copy in/out (cpio)– Common back-up utility– Includes options similar to the tar utility, but has

some added features including the ability to back up device files and long filenames

– Uses absolute pathnames by default when archiving


Table 13-6: Common options used with the cpio utility


Table 13-6 (continued): Common options used with the cpio utility

The dump/restore UtilityThe dump/restore Utility

• dump/restore– Can be used to back up files and directories to a

device or to a file on the filesystem– Can only work with files on ext2 and ext3

filesystems

• /etc/dumpdates– File used to store information about incremental

and full back-ups for use by the dump/restore utility


• Full back-up– An archive of an entire filesystem

• Incremental back-up– Archive of a filesystem that contains only files

that were modified since the last archive was created


Figure 13-1: A sample back-up strategy


Table 13-7: Common options used with the dump/restore utility


• restore command– Command used to extract archives created with the dump command

Table 13-7 (continued): Common options used with the dump/restore utility

Software InstallationSoftware Installation

• Package manager– System that defines a standard package format

and can be used to install, query, and remove packages

• Red Hat Package Manager (RPM)– The most commonly used package manager for

Linux

Compiling Source Code into Compiling Source Code into ProgramsPrograms

• The procedure for compiling source code into binary programs is standardized today among most Open source Software developers

• GNU C Compiler (gcc)– Command used to compile source code into

binary programs

Compiling Source Code into Compiling Source Code into ProgramsPrograms

Figure 13-2: The LTRIS program

Installing Programs Using RPMInstalling Programs Using RPM

• Packages in the RPM format have filenames that indicate the hardware architecture the software was compiled for, and end with the .rpm extension

• rpm command– Command used to install, query, and remove

RPM packages


Figure 13-3: The bluefish program


Table 13-8: Common options used with the rpm utility


Table 13-8 (continued): Common options used with the rpm utility


• GNOME RPM Manager– Graphical tool that may be used to install RPM

packages available with the GNOME desktop environment

• KDE Package Manager– Graphical tool that may be used to install RPM

packages available with the KDE desktop environment


Figure 13-4: The GNOME RPM Manager


Figure 13-5: The KDE Package Manager

Chapter SummaryChapter Summary

• There are many compression utilities available for Linux systems

• Files may be backed up to an archive using a back-up utility

• The tar utility is the most common back-up utility used today

Chapter SummaryChapter Summary

• The source code for Linux software may be obtained and compiled afterwards using the GNU C Compiler

• Package managers install and manage compiled software of the same format

• The Red Hat Package Manager can be used to install software in Red Hat Package Manager format

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Linux+ Guide to Linux Certification Chapter Thirteen Compression, System Back-Up, and Software Installation