UNIX LINUX Operating System

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UNIX & LINUX Operating System

Thanh-Hai DANG Information Systems Dept -VNUH

Email: haidt82@yahoo.com

“UNIX is user-friendly, but

UNIX also choose her friends very carefully”

Course statement

• Goal

– Usage, entire administration

– Not principles of OS

• Perspective

– A friend of UNIX

– Linux in place of Windows in your mind

– Curious for the principles of OS (Go inside into it)

• Materials

– UNIX/LINUX curriculum of Asoc Prof Thuy HQ,– Linux Complete Command Reference by J.Purcell – Securing and Optimizing Linux, Gerhard Mourani

UNIX OS.

Some characteristics

• Written in a high level language (C)

• User interface simple but powerful enough

• Good file system

• Simple connection to peripherals

• Multi User and Multi Process

• Relative independence between data and hardware

Unix Chronology.

• Ken Thompson at Bell Labs (1969)

– Withdrew from MULTICS project

– Written in assembler for a GE-645 machine– Dennis Ritchie

– First Release in 1971

– Bourne shell included

– Kernel largely rewritten to be more portable to other machine architectures

Chronology (Cont.)

• The 80’s

– /usr/group established in 1981

– X/OPEN (From many EU computer companies)

– IEEE from 1984 (enhancement of POSIX)

• 1984 : the birth of 3 versions

– System V from AT&T ( System III from 82)

– 4.2 BSD of Berkeley Uni, Base for many OS: Sun Microsystems (SunOS), Digital (Ultrix)…

– XENIX of Microsoft for PC (Compatible with System V)

Chronology (Cont.)

• At the end of 80’s, 2 organizations said hello

– UNIX International (UI)

• The agreement between AT&T and Sun : SVR4

(System V Release 4), The converged Edition of System V and BSD

– Open Software Foundation (OSF)

• IBM, Digital, HP, Bull, Siemens, Apollo, Nixdorf

Chronology (Cont.)

• LINUX OS came into our world (1991)

– Written by Linus Torvald at Univ of Helsinki

• For the Intel i386 family of processors

• Derived from MIMIX, one of the most successful version of PC UNIX

LINUX OS.

Some characteristics

• A typical OS for UNIX

• GUI thru X-Windows

• Many network protocols supported

• Real-time supported

• Parallel computing and PC Cluster

• Multi languages

Free Software, Linux & Open Source

• 1984 : Richard Stallman, The Father of GNU

(Gnu is Not Unix) found Free Software

Free Software, …(Cont.)

• 1993 : Rémy Card invented ext2 file system for Linux

• 1994 : Linux ported to the other CPU not Intel: Alpha, ARM, PowerPC, RISC, Sparc,

• 1995 : Apache Group built Web server Apache

Distributions Linux

• Distribution = A collection of all or some programs

altogether around a Linux kernel which allows to install a collaborative system, operating perfectly

– Include one or more CD ROM

– Easily installed,

– May be other softwares not GPL or OpenSource

included

Live CD Linux

• Distro Linux on one CD

– GNU/Linux OS Plus with necessary softwares

– Not affect the current status of PC, HD not required!

• Some typical distro

– Knoppix

– DemoLinux

– Mandows

– FreeSBIE

UNIX architect

Unix kernel architect

Shell system

• The command interpreter

– Show a prompt ($) and wait from keyboard

– Receive user’s commands

– Analyse commands: Name, option values and parameters

– Use kernel to initialize a process

– Wait for process to finish

• Programming language also

Shell …(Cont.)

• Bourne shell (sh) ($): Steven Bourne, AT&T

• Korn Shell (ksh) : David G Korn, AT&T

• C_Shell (csh) (%) : Bill Joy, UC Berkeley

• Tenex Shell (tcsh) (>) : extend of csh

• Bourne Again Shell (bash) (#) : Brian Fox, FSF (Linux)

Environment Variables

• Used by shell and some facilities (X11, mail, )

– $HOME: home directory of user

– $MAIL: mail name

– $PATH: List of path where commands are looked for( separated by :)

• Initialize after login

– script: bashrc, bash_profile

– echo <Var_Name>

• GNOME, KDE / X-Window (XFree86)

Command common structure

• # <Command_Name> [<options>] [<Parameters>]

– <options>:

• Reduced : #date –d <string>

• Full: #date –date=<string>

– Eg #ls –l test.cpp matrix.cpp

• Wild Card *, ?, [abc]

• #ls –l g*

Man Page

• Command man <command> :

– Show explanatory document for command

<command>

– Syntax + Options description + Examples

– <command> = command, library function, system file

• Note :

– Type ‘q’ to quit

– Command name exact

• Command man -k <keyword>

Man Page (Cont.)

• COMMAND(1) Linux Programmer’s Manual COMMAND(1)

• The scheme of inter-connecting between processes: cache memory + synchronization scheme

– read: wait if pipe empty

– Ghi (write): wait if pipe full

pipe-line (Cont.)

• Indicated by “|”

• Usefulness: Combine some simple tools to do complex functions

– Fast, right and simple

– Re-use concept in Software Engineering

• Eg

– Count the line of C sources in directory

$cat *.c | wc -l

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• Shutdown [options] <time> [alert]

– -r: Reboot right after system shutdowns

– -h: Halt officially right after system shutdowns

– -f: Quick reboot and abort disk checking

– -F: Reboot and check hard disk

– <time>: set shutdown time

• hh:mm or +<minute number>

Eg shutdown +1 shutdown after one minute!

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• Start and work in graphical model

– Allow to customize working mode of system

– Enumerated in /etc/inittab

# 0 – halt (Do NOT set initdefault to this)

# 1 – Single user mode

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• Start and work in graphical model

– Id:3: initdefault:  Id:5: initdefault:

– Use command $startx

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• Command for Showing and setting date and time

– Show: date [options] [+format]

– Set: date [options] [MMDDhhmm [ [CC]YY]

• Options

– -d, date=<string>: shows time in <string>

parameter, not show the current system time

– -f, file=<text_file>

– -I, iso-8601[=‘date’ | ’hours’ | ‘minutes’ | ‘seconds’]: Shows according to the standard ISO-8601 (2000-11-8)

Note: -I ~ iso-8601=‘date’

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• [+format]

– %%: show character %

– %a: Abbreviated weekday name in the locale (Wed for wednesday)

– %A: Full weekday name in the locale

– %b: Abbreviated month name (Mar for March)

– %B: Full month name

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• [MMDDhhmm[[CC]YY] used to set the current time of system

– MM: Two numbers indicate month

– DD: day index in month

– hh: hour in day

– mm: minute

– CC: Two numbers indicate century

– YY: Two number indicate year

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– -y: Display a calendar for the current year

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• Gets name and information about the current kernel

– uname [options]

• [options]

– -a, all

– -m, machine: processor architect

– -n, nodename: Computer name

– -r, release: OS kernel

– -s, sysname: Name of OS

– -p, processor: processor type

#uname –a

 Linux linuxsrv.linuxvn.net 2.2.14-5.0#1 Tue Mar 7 21:07:39 EST 2000 i386 unknown

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• Shell prompt

– $PS1: when entering command ($ or #)

– $SP2: when waiting for input data from keyboard

• How to change:

– # PS1=‘ <char_sequence>’

– # PS1=‘ < char_sequence>’

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• \! Display the command index in history

• \# Display the command index

• \$ Display $, for super user, that is #

• \\ Display \

• \d Display current date

• \h Display machine name

• \n New line character

• \s Display shell file name

• \t Display current time

• \u Display user name

• \W Display current directory name

• \w Display current directory full-path

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• Sample on changing $PS1 variable

– root@may1 /hda1]# PS1=‘[\h@\u \w : \d]\$’

 [may1@root /mnt/hda1 : Fri Oct 27 ]#

THIS LESSON ENDED

&

SEE YOU NEXT WEEK