Archiving, Compression, and Managing Software Packages Chapter Eleven Compressing Files • Compressing files – Useful way to use less space for rarely accessed data – Makes files smaller before transmitting them over network • gzip command – Compress any file; best compression 60-70% of original size – Lempel-Ziv Compression – gzip –v sample sample.gz – -v verbose option – zcat sample.gz to view compressed file contents • gunzip command – Uncompresses file compressed using gzip – gunzip –v sample.gz – Alternative: gzip –d sample.gz The gzip Utility (continued) 3 The gzip Utility (continued) The gzip Utility (continued) Compressing Files • bzip2 command – Compress any file; better compression than gzip – Burrows–Wheeler transform and Huffman coding – bzip2 –v sample sample.bz2 – -v verbose option – bzcat sample.bz2 to view compressed file contents • bunzip2 command – Uncompresses file compressed using gzip – bunzip2 –v sample.bz2 – bzip2 –d sample.bz2 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 – tar, cpio, dump/restore, burning software System Backup (continued) Using tar for Archiving Files • tar archive – Tape Archive – Single file that can contain other files and directory structure • tar command – Create tar archive – Specify files to be included in backup archive on command line – Writes data to file name or device The tar Utility (continued) The tar Utility (continued) Using tar for Archiving Files • tar and compress an entire directory’s contents – tar –zcvf backup.tar.gz * • View contents of archive – tar –ztvf backup.tar.gz * • tar to a tape device – tar –cvf /dev/st0 * • Extract and uncompress – tar –zxvf backup.tar.gz • Extract from a tape device – tar –xvf /dev/st0 • Tarball – archive and compressed – .tar.gz or .tgz Using tar and cpio for Archiving Files (continued) • cpio command – Copy in and out – Similar to tar – Reads from STDIN channel for file names – Writes data back to STDOUT – Examples • Archive • find /home –u horvathe | cpio –vocB –O horvathe.cpio • Extract • cpio –vicB –I horvathe.cpio • tar and cpio – Help create incremental or multilevel backup 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) A sample back-up strategy 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 • Ubuntu comes with k3b Disc Burner burning software • Fedora comes with Brasero Disc Burner burning software Managing Packages • Linux groups related files into packages for easier management • Software package contains all files needed to install and use application • Red Hat Package Manager format – Abbreviated as rpm • Debian Package Manager format – Abbreviated as deb Managing Packages (continued) • Debian package format – Used by Debian Linux distributions – .deb file extension – dpkg – old form for installing packages – apt – Advanced Packaging Tool – dselect - utility manages Debian packages Synaptic Package Manager in Ubuntu Using rpm to Manage Software Packages • rpm command-line utility maintains database listing all software packages installed on system – Lists: • Files included in each package • Packages are dependent on other packages • Other information • rpm command – Install new software packages – Erase software packages from system Using rpm to Manage Software Packages (continued) • Name of package file includes version information – Example • gedit-2.4.0-3.i386.rpm • Version 2.4.0 • Release code 3 • Platform i386 Using rpm to Manage Software Packages (continued) • Rpm command options fall into categories – -q option―query database and learn about packages – -i or -U option―install or upgrade package – -e option―erase (uninstall) rpm package – -f option: together with –q used to display the package to which a specific file belongs • Install new rpm files either from: – Linux CD-ROM – Internet Using rpm to Manage Software Packages (continued) • Install package zsh-4.2.0-1.i386.rpm – rpm -uvh /tmp/zsh-4.2.0-1.i386.rpm • Can use regular expression to specify package names • rpm utility maintains internal database of keys • Key is part of encryption information used to digitally sign rpm file Using rpm to Manage Software Packages (continued) • Fedora keys located in /usr/share/rhn • --import imports keys into rpm database • Check for keys – rpm --checksig -v packagefilename 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) 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) The KPackageKit utility alien • Converts RPM to DEB Packages • sudo aptitude install alien • Download rpm • sudo alien --scripts --to-deb avg75flm-r45- a0973.i386.rpm avg75flm_r45-1_i386.deb • Coverts to deb generated • Install Debian package • sudo dpkg --install avg75flm_r45-1_i386.deb Repairing Package Manager • sudo aptitude install -c – Checks apt – may need to be run if Synaptic package manager hangs • sudo aptitude install --fix-missing – sudo aptitude -f install • Fix packages; even • sudo dpkg --configure -a – Attempts to install all partially installed packages APT Tools • aptitude install package-name – Installs a package • aptitude reinstall package-name – Reinstalls a package • aptitude remove package-name – Removes a package • aptitude purge package-name – Removes package and configuration files • aptitude show packagename – Displays information about the package, including dependencies. • May also use apt-get for many commands APT Tools • aptitude update – Updates the list of available packages from the apt sources • aptitude upgrade – Upgrades installed packages to the most recent versions. • aptitude safe-upgrade – The safest way to upgrade is to use the action 'safe-upgrade'. The new action will upgrade a package only if it does not impact other packages, i-e: if it is necessary to add or remove a dependency package during upgrade, safe-upgrade won't upgrade APT Tools • aptitude full-upgrade – Upgrades installed packages to the most recent versions. aptitude will upgrade to the latest version of a package even if it is necessary to add or remove dependencies. • aptitude clean – Deletes packages in the APT cache. APT Tools • apt-cache search keyword – Searches for packages that match a keyword • apt-cache depends packagename – Display dependencies; packages that must be installed before this package can be used. • aptitude search packagename – Searches for packages have the packagename Repositories • Sites where packages can be downloaded • /etc/apt/sources.list • # comment • deb – executable • deb-src – source code dpkg • Monitors which software packages are installed • Location of packages • Dependencies • Will not download packages from a repository • dpkg --list packagename.deb – Information about packages • dpkg --install packagename.deb – Install packages • dpkg -- purge packagename – Delete package and configuration files dpkg • dpkg --status packagename – Displays information about an installed package • dpkg --search packagename – Search for packages with a name Updating the System Automatically – Download upgrades or security fixes for key operating system packages installed on system Software Updates in Ubuntu Updating the System Automatically • Red Hat Network – Download upgrades or security fixes for key operating system packages installed on system – Subscribe to Red Hat Network service • May be entitled to annual subscription as part of purchase • Individuals can use for free Updating the System Automatically (continued) • Red Hat Network – Uses icon on Panel in GNOME or KDE to indicate status • Check mark in blue circle • Flashing exclamation point in red circle – To register, double-click