operating systems 1

CO3030 Internet Scripting 2005 Chris Hutchison

CI1131 ICT1 LectureCI1131 ICT1 Lecture

Introduction to UNIX & Linux

CI1131 ICT1 : Introduction to UNIX & Linux Chris Hutchison

UNIX & the “ *NIX” familyUNIX & the “ *NIX” family

UNIX developed at AT&T Bell Labs, 19693 levels of the UNIX system: kernel, shell, and tools and applicationsmultitasking, multi-user, portable, vast suite of tools and applications, .... stable!has spawned 100+ *NIXes (incl. Solaris, FreeBSD, NeXTSTEP, Mac OS X, and Linux)


UNIXUNIX

The kernelthe core of the operating system, the kernel controls the hardware and turns part of the system on and off at the programer's command. E.g. if you ask the computer to list (ls) all the files in a directory, the kernel tells the computer to read all the files in that directory from the disk and display them on your screen.


UNIXUNIX

The shellThere are several kinds of shell, most notably the command driven Bourne Shell, C Shell, Korn shell, and BASH (Bourne Again SHell), and menu-driven shells (Midnight Commander, vsh, lash) that make it easier for beginners to use. Whatever shell is used, its purpose remains the same -- to act as an interpreter between the user and the computer.


UNIXUNIX

Tools and applicationsThere are hundreds of tools available to UNIX users, although some have been written by third party vendors for specific applications. Typically, tools are grouped into categories for certain functions, such as word processing, business applications, or programming. (Try typing, for example, apropos editor at the command prompt.)


Some UNIX referencesSome UNIX references

The Creation of the UNIX Operating Systemhttp://www.bell-labs.com/history/unix/

The Single UNIX Specificationhttp://www.unix.org/what_is_unix/

Unix Historyhttp://www.levenez.com/unix/

A Brief History of UNIXhttp://www.uwsg.iu.edu/usail/external/recommended/unixhx.html


LINUXLINUX

Project begun by Finnish student Linus Torvalds in 1991Strictly, Linux is just the kernel – the operating system itself is GNUMany popular *NIX alternatives also using GNU OS:

FreeBSD, BeOS, OpenBSD, NetBSD, ...


Linux is freeLinux is free

Linux mimics the form and function of a UNIX system, but (important!) is not derived from licensed source code, hence 'free'No one “owns” Linux: it it not a company or an organisation

Anyone is free to create a new “distribution”

Examples: Fedora, Debian, Mandriva, SuSE, Ubuntu, Gentoo, Centos, BLAG, Knoppix, Mepis, Sabayon, dyne:bolic, ... and around 100 or so others! See, e.g.

http://distro.ibiblio.org/pub/linux/distributions/


Linux directory structure [1]Linux directory structure [1]/

root directory of the entire system

/binholds system executables ('programs')

/sbinholds system executables essential for starting up the system

/bootholds the files (including the kernel) needed during the booting process


Linux directory structure [2]Linux directory structure [2]/dev

special directory that holds information regarding peripherals ('devices')

/homethe home directories for all users except root

/libsystem binary libraries, shared libraries and kernel module

/optwhere optional applications might go


Linux directory structure [3]Linux directory structure [3]/root

home directory for super user

/tmpwhere temporary files are stored, usually emptied on system restart

/varwhere variable system files go (system logging, file locks, printer spooling, mail spooling, web server, etc)

/etcholds almost all configuration files


Linux directory structure [4]Linux directory structure [4]/mnt

'mount point' for temporarily mounting other media, e.g. CD-ROM, USB drive, iPod, and other file systems

/usrholds application programs, source code, additional libraries, wallpapers, icons, etc

/usr/bincontains binary executables


LINUX: the X environmentLINUX: the X environment

Beyond the shell ... users are 'cushioned' from the shell by a GUI:

X server: handles communication between the hardware (in particular the graphic card) and software (the X programs) ... and nothing else

X client: displays graphics and graphical frontends

'windowmanager' (FVWM, Enlightenment, IceWM, ...): basic window functionality (menu, max, min, close, ...)

'desktop environment' (KDE, Gnome, ...): clickable icons, taskbar, general “look'n'feel”. Desktops also usually come bundled with applications.


The KDE desktopThe KDE desktop


KDE with CompizKDE with Compiz


KDE with KateKDE with Kate


Some Linux referencesSome Linux references

Linux Online (the place to start)http://www.linux.org

History of Linuxhttps://netfiles.uiuc.edu/rhasan/linux/

The GNU Operating Systemhttp://www.gnu.org

The Free Software Foundationhttp://www.fsf.org

operating systems 1

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