Jozef Goetz, 2009

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expanded by Jozef Goetz, 2008

Copyright © 2005 Pearson Addison-Wesley. All rights reserved.

Credits: Parts of the slides are based on slides created by textbook authors, Syed M. Sarwar, Robert Koretsky, Syed A. Sarwar

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Objectives

You may ignore last slides 63 – 69

To give an overview of the structure of a contemporary system

To describe briefly the structure of the LINUX/UNIX operating system

To detain some important system setups

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Objectives To introduce the LINUX/UNIX Text User Interface and

show the generic structure of LINUX/UNIX commands

To describe how to connect and log on to a computer running LINUX/UNIX operating system

To explain how to manage and maintain files and directories

To show where to get online help for LINUX/UNIX commands

To demonstrate the use of a beginner’s set of utility commands

To cover the basic commands and operators here and in coming chapters: alias, biff, cal, cat, cd, cp, exit, hostname, login, lp, lpr, ls, mesg, mkdir, more, mv, passwd, pg, pwd, rm, rmdir, talk, telnet, unalias, uname, whatis, whereis, who, whoami, write

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Computer System Hardware

Main/Primary Storage Central Processing Unit (CPU)

CPU clock: 3-4 G cycles per sec Disk Bus I/O Devices

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Computer System Hardware

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6Main/ Primary Storage

Purpose: To store executable programs or processes. Also called Volatile Storage place. Units: bit, byte, KB, MB, GB, TB

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8Disk

A storage place that contains all the computer system’s programs and applications

A nonvolatile storage place Disks are read and written in terms of

sectors and blocks Speed of a disk drive is dictated by its

Latency Time the speed at which the drive can spin

Seek Time the speed at which the head can move

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I/O Devices

monitor plotter scanner CD-ROM DVD Flash drives –USB, SD etc.

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10Bus A set of parallel wires used to carry

information in the form of bits from one sub-system in a computer to another

System Bus data Bus, address bus, control bus

carry data, address of main memory, control info respectively

Loader Program reads the apps from the disk into memory

Fetch, decode and execute operations form a machine cycle

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11Execution of the application

1. When the user types at command line the name of the executable program name and hits the <Enter> to run the application

2. The loader program reads the app from the disk and loads to the main memory

3. And it then sets the internal state of the CPU so that it knows the location of the program’s 1st instruction, next see next slide

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12Central Processing Unit (CPU)

4. CPU executes the programs by fetching them from the RAM, one instruction at a time

RAM

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13Central Processing Unit (CPU)

Every CPU has its own language called its instruction set

A CPU is functionally divided into two parts Control Unit Execution Unit (or Arithmetic and Logic Unit

(ALU))

The storage locations of CPU are called Registers (# of registers a few to a few 100s with size 32 or 64 bits)

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UNIX Operating System

UNIX/LINUX is a multiuser, multiprocess operating system.

Multiuser – multiple users can use the computer system simultaneously.

Multiprocess – system can run several processes (executing programs) at the same time.

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UNIX Operating System

UNIX is mostly written in C language. Thus, it allows UNIX to be portable to many architectures.

And portability implies a use in variety of computer environments.

In fact, UNIX/LINUX runs on wider variety of computer then any other operating system.

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LINUX/UNIX Software Architecture From bottom:

Device Driver Layer Mouse, DVD, printer drivers,

etc interacts with various

hardware devices user cannot execute them

as commands The LINUX/UNIX Kernel

Process Management Create, suspend, terminate

processes Ps IPC (Interprocess

Communications) mechanisms

Pipe: related Ps, same cmpters

Named Pipe: unrelated Ps, same cmpters

BSD socket – Ps communicate in >1 network

File Management Create, remove files, Create, remove directories

Main Memory Management Allocate, dealocate RAM for

Ps Disk Management

Allocate, dealocate, free and used disk space, disk scheduling for file read, write etc.

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17Interprocess Communications IPC

Communication channels: Pipe

>= 2 related processes on the same machines

Named pipe (FIFO) >= 2 related or unrelated processes

on the same machines BSD socket

>= 2 processes in a network (or on the Internet)

Internet software such as Web browsers, ftp, telnet, e-mail are implemented using sockets.

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LINUX/UNIX Software Architecture The System Call

Interface Entry points to Kernel

System Call: The invocation of an operating

system routine to manipulate Ps, files and other system resources

Operating systems contain sets of routines for performing various low-level operations.

For example, all operating systems have a routine for creating a directory.

If you want to execute an operating system routine from a program, you must make a system call.

Language Libraries For C, C++, C#, Java,

FORTRAN etc.

LINUX/UNIX Shell: Starts when you logon and

interprets cmds Bourne Again, TC, Z, etc.

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LINUX/UNIX Software Architecture

Applications Compilers, word

processors, spreadsheets, ftp, telnet, Web browser etc.

can get the kernel code by using

a library calls a higher level

interface to the kernel than system calls

eventually use system calls

a system call

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AUI vs API

The command interpreter (e.g., a LINUX/UNIX shell) of an operating system and the applications layer comprise the application user’s interface (AUI).

The language libraries and the

system call interface comprise the application programmer’s interface (API).

See previous fig.

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21Process States

Possible process (P) states running (using the CPU at that

instant) blocked (waiting for external

event, CPU can be available) the process must execute a system

call: block or pause to get into blocked state

e.g. P reads a pipe or special file (e.g. a terminal) and there is no input available, P is automatically blocked

ready (no CPU available for it)

Transitions (T) between states shown

2 and 3 caused by the process scheduler (PS)

2 occurs when PS decides that the running P1 has run long enough, and it is time to let another P have CPU

3 occurs when all the other Ps have had their fair share and it is time for P1 to get CPU to run again

4 occurs when the external event for which process was waiting (such as the arrival some input) happens

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 client–server software model

- the foundation for Internet applications

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23Logging On and Logging Off

Three basic ways of connecting to a LINUX/UNIX operating system:

1. Local Area Network Connection Intranet login: connect to a mainframe using terminal,

such as a VT-100 via a Sun workstation (which serves many terminals) Terminals are a dump graphical user interface to OS running on a

workstation A variation connect LINUX/UNIX workstation with a LINUX/UNIX

server

2. Internet Connection – federation of LANs and WANs windows telnet windows ftp PuTTY (the Telnet and SSH (secure shell) client itself) WinSCP WS_FTP_PRO or WS_FTP_PRO Explorer

3. Stand-alone connection A computer is not hooked up to a LAN, intranet, or the Internet

<Ctrl-D> - ending a session

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Connecting to UNIX PuTTY is a free implementation of Telnet

and SSH for Win32 and Unix platforms. More secure and easier to use then Telnet

Telnet is a terminal emulation program for the Internet. Not secure.

SSH (secure shell) is for UNIX/LINUX systems to provide authentication security for TCP/IP applications, such as FTP and Telnet. It can encrypt communications.

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25Connecting to UNIX via PuTTY

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26Connecting to UNIX via PuTTY

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Figure 3.5 Text-based login screen on a typical LINUX/UNIX computer

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3. Connecting via a Telnet Client on a Microsoft Windows Machine.

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Entering Commands

UNIX/LINUX philosophy : it assumes that users know what are they doing.

UNIX/LINUX is a command based system. It is important to remember all commands and what they do.

Commands in UNIX/LINUX are programs.

UNIX/LINUX is case sensitive. Date and date is not the same.

Most UNIX/LINUX commands are in lowercase.

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31Structure of a UNIX Command

where:$ is the shell prompt,anything enclosed in [ ] is not always needed,command is the name of the valid UNIX command for

that shell in lowercase letters,[-option(s)] is one or more modifiers that change

the behavior of command,[option arg(s)] is one or more modifiers that change

the behavior of the -option(s),[command arg(s)] is one or more objects that are

affected by command, generally files and pathnames.

Space separates command, option, option argument, and command argument, but no space is necessary between multiple options or multiple option arguments. Also, a space is optional between the option and the option argument.

$ command [[-]option(s)] [option arg(s)] [command arg(s)]

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32Structure of a UNIX command

$ ls

Contains only the command ls$ ls –la

Contains the command ls and two options l and a

$ ls –la m*

Contains the command ls, two options l and a and command argument m*

$ lpr –Pps15 hw5.ps

Contains the command lpr, one option P, one option argument ps15 and one command arguments hw5.ps

$ command [[-]option(s)] [option arg(s)] [command arg(s)]

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The date Command

Use the UNIX date command to display the system date, which system administrator maintains

r – last file modification [cs253u@shell cs253u]$ date -r my Sat Jan 24 10:31:20 PST 2009

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The cal Command

Displays the calendar of the current month : cal

Displays the calendar of 2000 : cal 2000

Displays the calendar of Feb 1977 : cal 2 1977

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35The who and finger Commands

In a multiuser system, knowing who is logged into the system maybe helpful

Use the who command to determine who is using the system and their current location : who

[cs253u@shell cs253u]$ whogchang pts/2 Jan 28 17:05 (d-ecs-17x-205.fullerton.edu)gchang pts/3 Jan 26 09:56 (d-ecs-17x-205.fullerton.edu)nan pts/4 Jan 30 18:04 (d-ecs-18y-188.fullerton.edu)

Use the finger command to find out details about user : finger username

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The clear Command

Use clear command to clear your screen; it does not have options or arguments : clear

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Command Line History

Access the command history with up ↑ and down ↓ arrow keys.

Pressing the up arrow key ↑ once recalls the most recently used command.

Each time the up arrow key ↑ is pressed, an older command is recalled.

Each time the down arrow key ↓ is pressed, the next command in command line history is displayed.

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38LINUX/UNIX Command Usage

Viewing the Contents of Files cat, more, type, echo

create the Contents of Files:$ cat > myfile This is an example of how to use the cat command to add plain text to a file

<Ctrl-D>

$ more myfileThis is an example of how to use the cat command to add plain text to a file

$

cat –n file // put line # on the displayed lines

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39File Maintenance Commands Creating, Deleting and Managing Files

cp, mv, rm, ls

$ cp myfile myfile2 //copy$ mv myfile2 renamed_file // rename $ rm renamed_file //remove

// restore it$ cp myfile myfile2 //copy

$ lsmyfile myfile2 renamed_file

$ ls –al...details$ ls –F // slash after each directory demo literature/$ ls –-help

Usage: ls [OPTION]... [FILE]...List information about the FILEs (the current directory by default).Sort entries alphabetically if none of -cftuSUX nor --sort.

-a, --all => do not hide entries starting with .. .bash_history .bash_profile .emacs my .mysql_history.. .bash_logout .bashrc .gtkrc mydir .zshrc

-A, --almost-all => do not list implied . and ..

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File and Directory Structure

•Get Home Directory: cd ~•Print Working Directory: pwd

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41File Maintenance Commands

Creating, Deleting and Managing Directories mkdir, cd, pwd, rmdir$ mkdir first

$ cd first

$ pwd

/usr1.b/bobk/first

$ cd ..

$ pwd

/usr1.b/bobk

$ cp myfile myfile2

$ ls my*

myfile myfile2

$ rmdir first

rmdir: first: Directory not empty

$

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The man Command

The man command displays UNIX online manual, called the man pages, for command-line assistance : man who Press the space key to see more

manual pages, one screen at the time. Press Ctrl+b to go to the previous

screen. Press q to exit man program.

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Table 3.3 Sections of the LINUX/UNIX Manual

2-3 used by developers

Help on LINUX Command

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44Help on LINUX/UNIX Command

Obtaining Help with the man Command man [options][-s section] command-list

$ man ls

LS(1) FreeBSD General Commands Manual LS(1) // related to section 1

NAME

ls - list directory contents

SYNOPSIS

ls [-ABCFGHLPRTWZabcdfghiklmnopqrstuwx1] [file ...]

DESCRIPTION

For each operand that names a file of a type other than directory, ls displays

its name as well as any requested, associated information. For each operand

that names a file of type directory, ls displays the names of files contained

within that directory, as well as any requested, associated information.

If no operands are given, the contents of the current directory are displayed.

If more than one operand is given, nondirectory operands are displayed first;

directory and nondirectory operands are sorted separately and in lexicographical

order.

The following options are available:

Press <SPACE> to continue, or q to quit q$ man read

$ man passwd // password info

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45Figure 3.6 Manual Pages first screen display for man passwd command

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46Help on LINUX/UNIX Command

$ man ls

LS(1) FSF LS(1)

NAME ls - list directory contents

SYNOPSIS ls [OPTION]... [FILE]...

DESCRIPTION List information about the FILEs (the current directory by default). Sort entries alphabeti¡ cally if none of -cftuSUX nor --sort.

-a, --all do not hide entries starting with .

-A, --almost-all do not list implied . and ..

$ ls –-helpUsage: ls [OPTION]... [FILE]...List information about the FILEs (the current directory by

default).Sort entries alphabetically if none of -cftuSUX nor --sort.

-a, --all do not hide entries starting with . -A, --almost-all do not list implied . and ..

$ man -s2 read // refer to section 2

$ man -k passwd // refers all the man sections that contain the keyword reference

chpasswd (8) - update password file in batchgpasswd (1) - administer the /etc/group filehtpasswd (1) - Create and update user

authentication filesldappasswd (1) - change the password of an LDAP

entrypam_localuser (8) - require users to be listed in

/etc/passwdpasswd (1) - update a user's authentication

tokens(s)passwd (5) - password filepg_passwd (1) - Manipulate the flat password filesaslpasswd (8) - set a user's sasl passwordsmbpasswd (5) - The Samba encrypted password

filesmbpasswd (8) - change a users SMB password

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Utility Commands

Examining System Setups whatis, whereis, whoami, which$ whoamibobk$ whereis mkdirmkdir: /usr/bin/mkdir$

[cs253u@shell cs253u]$ whatis whichwhich (1) - shows the full path of (shell) commands

[cs253u@shell cs253u]$ which dir/usr/bin/dir

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The whatis Command Sometimes man contains more

information then one wants to see. To display a brief summary of a

command use whatis command. The whatis shows only the name and

brief description that appears near the top of a command’s man page : whatis who

Use for help: cmd –-help man cmd whatis cmd

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Other Methods of Obtaining Help whatis

$ whatis login set setenvlogin(1) -sign on // 1 is the section #

set(1) -set runtime parameters for session

setenv(1) -change or add an environment variable

$[jgoetz jgoetz]$ whatis login

login (1) - sign on

[jgoetz jgoetz]$ whatis login set

login (1) - sign on

SET [set] (l) - Set run-time parameters for session

set (n) - Read and write variables

set [builtins2] (1) - bash built-in commands, see bash(1)

[jgoetz jgoetz]$ whatis setenv

setenv ( 3) - change or add an environment variable

LINUX/UNIX Command Usage

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The whereis Command

Locates binary, source and man page files for a command : whereis who

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The which Command

List which files are executed if the named commands are run as a command :

which who

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The uname Command

Determine the name of the operating system that your computer runs

[jgoetz jgoetz]$ unameLinux[jgoetz jgoetz]$ uname --helpUsage: uname [OPTION]...Print certain system information. With no OPTION, same as -s.

-a, --all print all information -m, --machine print the machine (hardware) type -n, --nodename print the machine's network node hostname -r, --release print the operating system release -s, --sysname print the operating system name -p, --processor print the host processor type -v print the operating system version --help display this help and exit --version output version information and exit

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The grep Command

grep - global regular expression print Searches a file for a pattern utility searches through file (o directories) to see if contains

a specified string of characters

-bash-2.05b$ grep 'initialization' sum# initialization of variables

-bash-2.05b$ who | grep 'cs253u2'cs253u2 pts/16 May 9 10:37 (10.67.28.199)

[jgoetz academia]$ cat jozef.html| grep head<head></head>

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Utility Commands Printing and General Utility

Commands lpr, cal

$ lpr -Pprintname file_name $ lpr –Pcs200 file_name // print your file in CS200 at the

printer designated // as cs200 - you can find this

format by entering // $help => look for “printing” $ cal // display calendar$ cal 11 2004

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Command Aliases The alias command can be used to create pseudonyms

(nicknames) for commands they can be placed in ~/.profile or ~/.login but typically in

a shell start files .bashrc (.cshrc for TC shell)

Syntax for the alias command is: alias [name [ = string ] …] // for Bourne, Korn, Bash shells

alias l=‘ls –la’ alias [name [ string ] ] // C shell

alias l ‘ls –la’ alias

list all aliases

remove it unalias ls // remove ls unalias –a // remove all

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56alias Command Examples

The \!* string is substituted by the actual parameter passed to the given command

For dir command, the shell actually executes the ls -la

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Table 3.4 Useful Commands for the Beginner (continued on next slide)

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60Correcting Mistakes

<Ctrl-D> to log off, at the shell prompt

for Bash shell

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Configuration Shells

~ is a shorthand for your home directory

[jgoetz jgoetz]$ whereis bash bash: /bin/bash /usr/man/man1/bash.1.gz[jgoetz jgoetz]$ whereis csh csh: /bin/csh /etc/csh.cshrc

[jgoetz jgoetz]$ whereis profileprofile: /etc/profile /etc/profile.d

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Logging Out of UNIX

Logging out ends your current process and indicates to UNIX that you are finished.

Logging out depends on the shell. In C shell, type logout.

For Bourne, Korn or Bash shells type exit or press ctrl+d.

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63pine – E-mail System on CSE

Allows to send and receive e-mail. The most extensive and friendly e-mail

program for UNIX. To start pine:

Type pine and press <Enter>, the pine Main Menu will appear.

To exit pine: At almost any place in pine press q – for quit.

You are asked: really quit the pine. Press y – for yes and press <Enter>.

Up ↑ and down ↓ arrow keys help navigate the cursor.

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pine - Main MenuL – go the folder list

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65pine – Composing a Message

• To compose a message press c .

• The ^ character indicates the control key. •Ctrl key must be pressed down while the letter for each command is pressed too.

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Test Message to Yourself

1. Press c to compose.2. In the To field type email address and

press <Enter>.3. In the Cc field press <Enter>.4. In the Attachment field press <Enter>.5. In the Subject field type Test and press

<Enter>.6. Below the Message Test line type This is

a test.7. To send a message press ^x ( ctrl + x ) .

You are asked: Send a message?8. Press y or press <Enter>.

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Reply / Forward Message

To reply To replay to a selected or a currently viewed

message press r. You are asked whether you want to include

the original message in your replay. Also, if the original message was sent to more

then one person, you are asked if you want to replay to all recipients.

To forward To forward a selected or a currently viewed

message press f. Enter the email address and send as usual.

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Summary

In UNIX?LINUX, you communicate with the operating system programs through an interpreter called the shell, which interprets the command entered from keyboard.

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Metric Units

The metric prefixes