UNIX History and Philosophy

1
UNIX History and Philosophy

• Life with Unix

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Definition of an Operating System (OS)

• An operating system is a control program for a
  computer that performs the following operations
• manages and allocates computer resources
• schedules routine tasks
• provides a platform to run application software
  for users to accomplish tasks
• provides an interface between the user the
  computer

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History of Unix OS

• Prior to Unix, many operating systems ran
  collections or batches of operations one at a
  time.
• This single-user batch-processing approach did
  not take advantage of the potential processing
  power and speed of computers
• Note batch processing lacks the advantage of
  immediate feedback as opposed to online processing

Enter data in files to be later processed
Process Collection or Batch of files
Receive information of processed data
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History of Unix OS

• The Unix OS was developed (based on Multics
  CTSS operating systems) by Ken Thompson at the
  ATT Bell Laboratories in 1969. He wanted to
  create an multi-user operating system to run
  space wars game.
• Kens philosophy was to create an operating
  system with commands or utilities that would do
  one thing well very well (i.e. UNIX).

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History of Unix OS

• The first versions of UNIX were written in
  machine-dependent program (such as PDP-7).
• Ken Thompson approach Dennis Ritchie developer of
  C program), and in 1973 they compiled UNIX in C
  programming language to make operating system
  portable to other computers systems.

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History of Unix OS

• Ken Thompson (recently retired from Bell Labs) is
  on left, and Dennis Ritchie is in the middle.
  Whats his name is on the right

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History of Unix OS

• The Unix OS is a multi-user OS allowing more that
  more person to directly communicate with the
  computer.
• Although the OS can only work on one task at a
  time, a small piece of time (time slice) is
  dedicated to each task or user - this is referred
  to as time-sharing.
• Time sharing gives the illusion that the CPU is
  giving all the users its full attention

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An Illustration of Time-Sharing
User 1
User 8
User 2
User 7
TIME
User 3
User 6
User 4
User 5
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Development of Unix OS

• Unix became a popular OS among institutions such
  as colleges universities through a 4-year try
  before you buy deal.
• Efficient and inexpensive way of networking
• promotes Internet use and file-sharing
• Open system allows for source code to be shared
  among many programmers - allows for better
  coordination among programmers

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Development of Unix OS

• Students at University of California (in Berkley)
  further developed the UNIX operating system and
  introduced the BDS version of Unix

Unix
Berkley Software Distribution (BSD)Free
Bell LabsUNIX System V (5)Proprietary
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Development of Unix OS

• There were versions of UNIX for the Personal
  Computer (PC), such as XENIX, etc., but they
  didnt catch on in popularity until Linux was
  developed in the early 90s.

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History of Linux

• Linux operating system developed by programming
  student Linus Torvalds
• Linus wanted to develop Unix-like OS just to
  experiment with new 386 computer at the time...

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Why Has Linux Become soPopular?

• Linus decided to make Linux OSsource-code for
  Linux Kernel open to all
• Unlike traditional Operating Systems, anyone can
  modify and distribute Linux OS (as long as they
  distribute source code of Linux Kernel)
• Competition among Hackers allow code to be
  improved and distributed often
• Many users can spot bugs in the operating system
  or application if source code is open

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Why Has Linux Become soPopular?

• Other Factors
• PCs have increased processing power and a there
  has been a noted shift from mainframes and
  minicomputers to PCs.
• Since Linux is a Unix Work-alike, this OS has a
  reputation to be a very stable platform for
  networking (creating at-home servers) and running
  / maintaining applications.
• Agencies such as Free Software Foundation created
  GNU project to provide free software.

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Concerns

• Some people claim that there are as many version
  of Linux as there are users
• POSIX (Portable Operating System Interface for
  Computer Environments) is a government standard
  to ensure consistency among different UNIX and
  Linux versions.
• Many versions of Linux are approaching POSIX
  standard.

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Concerns

• Freedom of allowing Linux users to create
  servers connected up to Internet can lead to
  attacks from experienced hackers.
• Linux commands may be considered
  user-unfriendly although GUIs are now used.
• Prior reputation for difficult install process
  including the loss of data on other hard disk
  partitions.
• The same can be said of Microsoft Windows

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The Unix philosophy in a Nutshell

• The tenets of the Unix philosophy are deceptively
  simple. They are so simple, in fact, that people
  tend to regard them as having little importance.
  That's where the deception comes in. Their
  simplicity disguises the fact that these ideas
  are incredibly effective when carried out
  consistently.
• The following list will give you an idea of what
  the Unix philosophy tenets are. The rest of the
  book will help you to understand why they are
  important.

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Unix Tenets

1. Small is beautiful.
2. Make each program do one thing well.
3. Build a prototype as soon as possible.
4. Choose portability over efficiency.
5. Store data in flat text files.
6. Use software leverage to your advantage.
7. Use shell scripts to increase leverage and
   portability.
8. Avoid captive user interfaces.
9. Make every program a filter.

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Unix Tenets

• The preceding list contains tenets about which
  Unix developers are dogmatic. You will find
  similar lists in other books on Unix, as they are
  the points that everyone considers to be
  foundational Unix concepts. If you adopt them,
  you will be considered to be a "Unix person."

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Unix Lesser Tenets

• The following lists 10 lesser tenets, ideas that
  tend to be part of the Unix world's belief
  system.2 Not everyone involved with Unix is
  dogmatic about these, and some of them aren't
  strictly characteristic of Unix. Still, they seem
  to be a part of the Unix culture (and the Linux
  culture by inclusion).

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Unix Lesser Tenets

1. Allow the user to tailor the environment.
2. Make operating system kernels small and
   lightweight.
3. Use lowercase and keep it short.
4. Save trees.
5. Silence is golden.
6. Think parallel.
7. The sum of the parts is greater than the whole.
8. Look for the 90-percent solution.
9. Worse is better.
10. Think hierarchically.

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Unix Tenets

• After reading the list of tenets, you may be
  wondering just what all the fuss is about. "Small
  is beautiful" is not such a big deal. "Doing one
  thing well" sounds pretty narrow-minded in and of
  itself. Choosing portability over efficiency
  isn't the sort of idea that will change the
  world.
• Is that all there is to Unix? Is Linux just a
  small operating system for small minds?

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Unix Tenets

• Perhaps we should mention that Volkswagen built a
  marketing campaign around the "small is
  beautiful" concept that helped it sell millions
  of automobiles. Or consider that Sun
  Microsystems, a leading Unix systems vendor,
  based its strategy on putting "all the wood
  behind one arrowhead" or, in other words, "doing
  one thing well." Could all the interest in PDAs,
  wireless Web access, and hand-held video have
  something to do with portability?

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Unit Tenets

• Come. Let us begin the journey.
• 2Given words such as "dogmatic," "tenets," and
  "belief system," might one wonder whether the
  Unix philosophy describes a cultural phenomenon
  in addition to a technological one.

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Introduction to Unix/Linux

• Chapter One
• The Essence of UNIX

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Objectives

• Define operating systems in general and the UNIX
  operating system in particular
• Describe Linux as it relates to UNIX
• Explain the function of UNIX shells
• Describe the options for connecting to a UNIX
  system
• Define the syntax used for entering UNIX commands

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Objectives (cont.)

• Use the date, cal, who, man, whatis, and clear
  commands
• Perform basic command-line editing operations
• Enter multiple commands on a single command line
• Recall a command from the command history
• Log in to and log out of UNIX

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Understanding Operating Systems

• Operating System (OS)
• The most fundamental computer program
• Enables you to store information, process raw
  data, use application software, compile your own
  programs, and access attached hardware, such as a
  printer or keyboard
• UNIX Operating System
• Leading OS for workstations, which are computers
  on a local area network (LAN)

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Understanding Operating Systems
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PC Operating Systems

• A personal computer (PC) OS conducts all the
  input, output, processing, and storage operations
  on a stand-alone computer

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Mainframe Operating Systems

• A mainframe OS controls a large computer system
  with multiple processors that conduct input,
  output, processing, and storage operations for
  many users

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Network Operating Systems

• A network OS controls the operations of a server
  computer, sometimes called a host, which accepts
  requests from user programs running on other
  computers, called clients

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Server-based vs. peer-to-peer networks

• Server-based network
• Centralized processing approach
• Data and applications server resident
• If server fails, entire network fails
• Peer-to-peer
• Distributed processing approach
• Data and applications workstation resident
• Each system is both a server and a client

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Introducing the UNIXOperating System

• UNIX can be used on systems functioning as
• Dedicated servers or client workstations in a
  server-based network
• Client/server workstations connected to a
  peer-to-peer network
• Stand-alone workstations not connected to a
  network

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Introducing the UNIXOperating System

• UNIX is a multi-user system
• Allows many users access and share the resources
  of a server computer
• UNIX is a multitasking system
• Allows user to execute more than one program at a
  time
• UNIX is a portable operating system
• Used in many computing environments

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UNIX Concepts

• Shell
• The interface between user and OS
• Hierarchical Structure
• Directory and subdirectory organization
• Layered components
• Layers of software surround the computers inner
  core

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Linux and UNIX

• Linux is UNIX-like
• Not written from traditional UNIX code
• Linux is original code
• Includes POSIX standards
• Other Linux information
• Created by Linus Torvalds
• Offers all the complexity of UNIX
• Linux can coexist with other OSs

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Introducing UNIX Shells

• A shell is a UNIX program that interprets the
  commands you enter from the keyboard

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Choosing Your Shell

• Shells interpret commands and act as first-class
  programming languages
• A default shell is associated with your account
  when created Bash is the default shell in Linux
• A short list of some UNIX shells
• Bourne
• Cshell
• Korn
• Bash

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Choosing User Names and Passwords

• To use UNIX, a user must log in by providing a
  unique user name and password
• UNIX system administrators create accounts by
  adding user names and passwords
• Users log in to UNIX or Linux systems as long as
  they have accounts on the workstation or host
  (server) computer

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Connecting to a UNIX System

• Remotely through Telnet/Secure Shell
• Through network client software
• As peer on peer-to-peer network
• On a stand-alone PC
• Through a dumb terminal

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Connecting to UNIX

• Telnet
• terminal emulation software
• Easy and unsecure
• Secure Shell
• Terminal emulation software
• Session encrypted end-to-end
• Bundled with secure ftp and copy
• X-Windows

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Connecting to Unix

• Widows Clients
• telnet (native to windows)
• Terra Term (http//hp.vector.co.jp/authors/VA00241
  6/teraterm.html)
• Freeware Win32 telnet client
• Putty (http//www.chiark.greenend.org.uk/sgtatham
  /putty/)
• Freeware Win32 Secure Shell Client/Suite
• X-Win32 (http//www.starnet.com/)
• Commercial X-Windows Server for Windows
• Exceed (http//hummingbird.com)
• Commercial X-Windows Server Suite for Windows

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Logging in to UNIX

• Log in by entering username and password when
  UNIX system booted or connected to
• Enter at prompt (command-line mode) or into login
  box (GUI mode)
• Youre at the Shell prompt -- Now commands can be
  issued at the command prompt

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Logging In to UNIX

• Telnet can be accessed from a the console, or
  terminal window (after X-Windows is started)

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Entering Commands

• To interact with UNIX, a command is entered at
  the command prompt
• UNIX is case-sensitive and most commands are
  typed in lower case
• Two categories of commands
• User-level perform tasks
• System administration system management

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Entering Commands

• The date command
• Displays the system date, which the system
  administrator maintains
• The cal command
• Shows the system calendar
• The who command
• Shows who is using the system and their current
  location

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Entering Commands
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Entering Commands
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Entering Commands
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Entering Commands

• Command-line editing
• Certain keystrokes perform command-line editing
  (shell dependent)
• Multiple command entry
• More than one command on one line by separating
  with a semicolon()
• The clear command
• Clears the current screen

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Entering Commands

• Command-line history
• Use up and down arrow keys to scroll through
  command history
• The whatis command
• Displays a brief description of a command for
  help purposes
• Note the numbers in ()s that is the man section

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Entering Commands

• The man program displays the UNIX online
  reference manual, called the man pages, for help
  purposes

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Logging Out of UNIX

• Logging out ends your current process and
  indicates to UNIX that you are finished
• Logging out is shell dependent
• Bourne, Korn, Bash exit command
• C shell logout command

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Understanding the Role of the UNIX System
Administrator

• System administrator manages the UNIX system
• Adds users and deletes old accounts
• Also called the superuser
• Unlimited permission to alter system
• Unique user name root
• Prompt ends with (pound) symbol
• Normal user prompt (dollar) (percent) symbol

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Changing Passwords

• For security purposes, changing passwords is
  necessary
• Use the passwd command
• UNIX allows new password if
• The new password differs by at least three
  characters
• It has six or more characters, including at least
  two letters and one number
• It is different from the user name

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Viewing Files with cat, more, less, head, and
tail Commands

• Use cat, more, less and tail to view file
  contents
• cat displays a whole file at one time
• more displays a file one screen at a time,
  allowing scroll down
• less displays a file one screen at a time,
  allowing scroll down and up
• tail displays the end of a file
• head displays the beginning of a file

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Viewing Files with cat, more, less, head, and
tail Commands

• Use head and tail to view the first few or last
  few lines of a file
• head displays the first few lines
• tail displays the last few lines

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Redirecting Output

• The greater than sign (gt) is called a redirection
  symbol
• Create a new file or overwrite an existing file
  by attaching (gt) to a command that produces
  output
• To append to an existing file, use two
  redirection symbols (gtgt)

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Chapter Summary

• The operating system controls all computer
  resources and provides the base upon which
  application programs can be used or written
• A server-based network is centralized where
  security and maintenance are handled by the
  system administrator and all systems rely on the
  server a peer-to-peer network is decentralized
  where security and maintenance is distributed to
  each system and if one of the systems fails, the
  network continues to function

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Chapter Summary

• UNIX is a multi-user, multitasking operating
  system
• UNIX systems may be configured as servers or as
  client workstations in a server-based network, as
  client/server workstations in a peer-to-peer
  network, or stand-alone workstations when no
  network connection

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Chapter Summary

• The concept of the layered components that make
  up an OS originated with UNIX
• Linux is a UNIX-like OS and can coexist with
  Windows and MS-DOS
• In UNIX, you communicate with the OS programs
  through an interpreter called the shell and UNIX
  provides shells such as the Bourne, Korn, and C
  shells, with Bash being the most popular on Linux
  systems

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Chapter Summary

• In UNIX, the system administrator sets up
  accounts for users that supply a username and
  password
• You work with UNIX by typing commands that you
  can learn by referring to the online manual
  called man pages commands have specific syntax
  and allow you to see brief descriptions of
  commands, see who is logged in, display the
  system calendar, and log out

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Chapter Summary

• Most shells provide basic command-line editing
  capabilities and keep a history of your most
  recently used commands
• You can view the contents of files with view
  commands such as cat, less, more, head, and tails

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