Transcript No Slide Title

UNIX---Operating System
Overview and Introduction
Name: Ying LIU
ID: #103792
Contents
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Overview
History
Variants
Architecture
Commands
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Files and Directories
Security
Application
Conclusion
UNIX Overview
• What is UNIX?
– narrow sense: is a computer operation system
– wider sense: encompasses a broad set of
commands, or “utilities”
• What does it do?
– operates a computer
– lets a number of programmers access the
computer
• The Uniqueness of UNIX
– Multitasking capability
• Running more than one tasks at same time
– Multiuser capability
• multitasking permits multiple users to use the
computer
– Portability
• move from one brand of computer to another with a
minimum of code changes
– UNIX programs
• Integral utilities
• Tools
– Library of application software
UNIX History
• Bell Lab
• Ken Thompson
Dennis Ritchie
Doug McIlroy
Brian Kernighan
• 1960s--dependable
timesharing OS
• 1970--PDP-7, CTSS,
Multics
• 1974--rewritten in C
• 1975--Version 6
Table 1 Early versions of the UNIX system
----------------------------------------------------------------------------------------------------------------------------Version
Year released
Applications
-----------------------------------------------------------------------------------------------------------------------------Version 6
1975
Universities
Version 7
1978
Universities and commercial. The basis for System V.
System III
1981
Commercial
System V, Release 1 1983
Commercial
System V, Release 2 1984
Commercial, enhancements and performance improvements
Version 8
1985
Universities
Version 9
1986
Universities
Version 10
1989
Universities
-------------------------------------------------------------------------------------------------------------------------------* In addition, there are several university versions, the most important being the UNIX-Berkeley BSD
distributions.
UNIX SVR4
XENIX
UNIX
SVR3
4.2BSD
SUN OS
SVR4 compatibility
Figure 1. Relationship of UNIX System Variants with UNIX SVR4
UNIX Variants
--------------------------------------------------------------------------------- ----------------------------------------------------------
SOLARIS
Sun Microsystems
UNIXWARE
HP-UX
Novell
Hewlett-Packard
1991-SunOS
1991-Salaris 1.0
…….
1998-Solaris 7(2.7)
1999-UnixWare 7.1
1986-first version
1997-HP-UX 11.0
1991
LINUX
Linus Torvalds
SCO UNIX
Santa Cruz Operation
IRIX
Silicon Graphics
AIX
IBM
Tru64 UNIX
Compaq
ULTRIX
Digital Equipment Corporation
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UNIX Architecture
• Kerenel
– schedules tasks and manages storage
• Shell
– connects and interprets users' commands
– calls programs from memory and executes them
• Tools and Applications
– offer additional functionality to the operating
system
Tools
Shell
Kernel
Hardware
Applications
Figure 2. General UNIX Architecture
Types of Shells
Types
Programmer
Company
Language First Release
--------------------------------------------------------------------------------------------------------------------------------Bourne Shell
Stephen Bourne
AT&T
Algol
V7UNIX, late1979
C Shell
Bill Joy
Korn Shell
David Korn
Univ. of California, Berkeley
AT&T
C
2BSD UNIX, late 1970s
Algol
SVR4 UNIX, mid 1980s
______________________________________________________________________________________
• Function of Shells
– Interpret commands entered at the command
line prompt when running interactively.
– Customize the user’s environment, normally
done in shell initialization files
– Be used as an interpreted programming
language
• Tools and Applications
– hundreds of tools available
– certain functions
• such as word processing, business applications, or
programming
UNIX Commands
• Types of Commands
– Aliases--define within the shell’s memory
– Built-in commands-- are internal routines in the
shell
– Functions-- define within the shell’s memory
– Executables programs --reside on disk
• Generic Syntax
– Command [flags] argument1 argument2…
• Basic Commands
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logging on (rlogin)
changing password (passwd)
getting out (exit), listing files (ls)
copying files (cp)
removing files (rm)
navigating the directory tree (cd)
so on.
UNIX Files and Directory
• Hierarchical file system
– files are organized in a top-down, or inverted
tree, structure
• Tree-structured directory
• Four types of file system:
– Regular file system: Files that contain information
entered in them by a user, an application program,
or a system utility program.
– Directory file system: contains a list of file names
plus pointers to associated inodes (index nodes)..
– Device file system: used to access peripheral
devices, such as terminals and printers. Each I/O
device is associated with a special file.
– Named file system: named pipes. A pipe is a
circular buffer allowing two processes to
communicate on the producer-consumer model.
UNIX Security
• Risk and Treat
– Risk: the possibility of an intruder attempting to
access
– Treat: the motivation to attempt to gain
unauthorized access
• Protection
– Password system
– Intrusion detection
• There are four general categories of attack:
– Interruption: an asset of the system is destroyed
or becomes unavailable or unusable. This is an
attack on availability.
– Interception: an unauthorized party gains access
to an asset. This is an attack on confidentiality.
– Modification: an unauthorized party not only
gains access to but tampers with an asset. This
is an attack on integrity.
– Fabrication: an unauthorized party inserts
counterfeit objects into the system. This is an
attack on authenticity.
• Table 2 Network Security Architecture
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----------------------------------------------------------------------------------------------Layer
Name
Functional Description
----------------------------------------------------------------------------------------------Layer 7
Policy
Policy Definition And Directives
Layer 6
Personnel
People Who Use Equipment And Data
Layer 5
LAN
Computer Equipment And Data Assets
Layer 4
Internal-Demark Concentrator - Internal Connect
Layer 3
Gateway
Functions For OSI 7, 6, 5, 4
Layer 2
Packet-Filter
Functions For OSI 3, 2, 1
Layer 1
External-Demark Public Access - External Connect
---------------------------------------------------------------------------------------------
UNIX Applications
• Horizontal applications
– not specific to any particular industry. Are used
throughout academia, government, and the
commercial world
• Vertical applications
– are used for applications designed to solve
problems in specific industries such as retailing,
hotel management, or finance.
Conclusion
• Many of UNIX’s approaches and notations
have influenced the entire span of
subsequent operating systems.
• “Thirty years after its creation, UNIX still
remains a phenomenon!”.
References
•
Ellie Quigley: UNIX Shells by Example, second edition.. 1999 by Prentice Hall PTR. ISBN 0-13-0212229.
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Stephen Prata, Donald Martin, The Waite Group: UNIX System V Bible--Commands and Utilites..
1987 by The Waite Group, Inc. first edition. ISBN: 0-672-22562.
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Ralph M. Stair and George W. Reynolds: Principles of Information System, Fourth Edition. 1000 by
Course Technology. ISBN 0-7600-1079-X.
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William Stallings: Operating Systems: Internals and Design Principles. Third Edition. 1998 by
Prentice hall Engineering, Science & Math. ISBN 0-13-887407-7.
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Kenneth H Rosen, Douglas A Host, James M. Farber, Richard R Rosinski. UNIX: The complete
Reference. 1999 by The McGraw-Hill Companies. ISBN 0-07-211892-X.
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http://www.bell-labs.com/history/UNIX
http://www.msoe.edu/~taylor/4ltrwrd/
Acknowledgment
• I gratefully thank Professor M. Anvari for
the suggestion on the paper organization.