Linux Introduction What is Linux? How do you use it?

cs490ns - cotter2 Outline Linux Background Linux Basic Structure Linux User Interface Linux Commands

cs490ns - cotter3 History Linus Torvalds (Finnish student) looked for a development version of UNIX (other than Minux). Objective was to develop an open source version of UNIX that was functionally identical, but source code independent (as a hobby) Focus on the core operating system (the kernel) Project took on its own life. Version 1.0 released March, 1994

cs490ns - cotter4 Design Capabilities Multi-tasking Multi-user Multi-processing (multiple processors) Architecture Independence File system Flexibility Paging Memory Protection (protected mode) Networking

cs490ns - cotter5 Kernel vs Distribution Kernel provides core OS functionality –managed by Linux.org (Torvalds, et.al.) Distribution provides installation and package management needed to implement a complete OS including applications –Red Hat (Fedora) –CentOS –Ubuntu –SuSe –Debian –many others

cs490ns - cotter6 System Organization Like UNIX... Predefined root directory structure with preferred locations for kernel files / (root) bin boot dev etc home lib mnt proc root sbin tmp usr var

cs490ns - cotter7 System Organization DirectoryPurpose /The root directory, which is the top of the file system. /binCritical executables needed to boot the system. /devDevices connected to the system, such as terminals, disks, tapes, modems, etc. /etcSystem configuration files, including passwords, network addresses and names, system start-up settings, etc. /homeLocation of users directories. /libThe home of various shared libraries for programs.

cs490ns - cotter8 System Organization DirectoryPurpose /mntThe point where file systems exported from another system are temporarily mounted. /procImages of currently executing processes on the system. /tmpTemporary files that are cleaned up during the boot operation. /usrA variety of system files, including standard system utilities (/usr/bin), manual pages (/usr/man), headers for C programs (/usr/include), and administration executables (/usr/sbin). /varDirectory that stores log files (/var/log) and temporary storage space for services (such as spooling for mail, printers, etc.)..Current directory...The directory just above the current directory.

cs490ns - cotter9 Linux Security File Level Security –Authentication - allow only authorized users into the system (user name, password) –Access control - Ensure that resources (files) are only used by authorized users. (user id, group id, mode bits) System Level Security –Many of the same weaknesses as UNIX, since the basic design is the same –Open source: Makes it easy for hackers to analyze the system Easy for testers to fix the system when bugs are found.

cs490ns - cotter10 User Interface Options Command Line Interface –Primitive Interface that requires little system support –Used on Embedded systems, old systems, some servers –All Linux (UNIX) functions (commands) originally developed for command line. –Commands defined in man 1 (See also “Running Linux”) –Change to GUI with “startx”

cs490ns - cotter11 User Interface Options Graphical User Interface –Based on X Windows System X Server to generate display (bitmap) X Client to present display to Video monitor –Manages basic graphical display configuration Display Resolution Monitor type Video Card Input Devices –Use Window Managers to provide GUI

cs490ns - cotter12 User Interface Options GNOME –GNU Network Object Model Environment –Uses “Enlightenment” or “Sawfish” WM –Based on CORBA Architecture to support interaction between objects (applications, components, etc.) –Uses Nautilus File Manager

cs490ns - cotter13 User Interface Options KDE –K Desktop Environment –Heavy use of Drag-and-drop –Includes Kongueror File Manager Integrates local file management with Web browsing –Often extensive list of “K” applications and applets available.

cs490ns - cotter14 Commands Installation / Update Schedule Programs / Jobs Check / Change Environmental Variables Manage Processes

cs490ns - cotter15 Installation / Update Based on “packages” that include all files associated with an application / function Includes configuration information – directory locations, linkage to existing system config files. Most common is rpm – Red Hat Package Manager –Developed by Red Hat, but supported by many Linux Distributions –Provides a method to test, verify, install, uninstall or upgrade software (packages)

cs490ns - cotter16 Automatically Schedule Programs

cs490ns - cotter17 Manually Schedule / Run Programs cron –System program that will schedule jobs crontab –Users controlled by /etc/cron.allow or /etc/cron.deny –Specify H Min D Mon DOW command –crontab –5 * 1,15 * * echo “turn in timesheets!” | mail cotterr – “^D”

cs490ns - cotter18 Manually Schedule / Run Programs at –Users controlled through /etc/at.allow or /etc/at.deny –Specify time [date] of execution –provide list (file) of commands / jobs to execute –at 11:21 Jan 5 –at> /home/cotterr/bin/myscript.sh –at> cp /home/cotterr/info.txt /home/backup/info.txt –at> “^D”

cs490ns - cotter19 Environmental Variables printenv –Display all environmental variables echo $PATH –Display the contents of a single variable set $PATH=“$PATH:/sbin” –Temporarily add “/sbin” to search path set –Display all current variables

cs490ns - cotter20 Manage Processes ps –Print status of all of your active processes ps aux –Print status on all active processes kill –s 9 PID –Terminate a process with process id PID

cs490ns - cotter21 SUMMARY Linux Background Linux Basic Structure Linux User Interface Linux Commands