The Internet on Unix

• "History of the internet" is an animated documentary explaining the inventions from time-sharing to filesharing, from Arpanet to Internet. http://youtu.be/9hIQjrMHTv4
• History Channel Presents The Internet (47 mins) http://youtu.be/aKi-cj39-xg
• A brief history of the Internet, MIT OpenCourseWare, (51 mins) http://youtu.be/oIezCGjxV3A

Introducing UNIX

• Operating Systems 1 - Introduction (4 mins) http://youtu.be/5AjReRMoG3Y
  • multiprogramming (multitasking) and multiuser
  • manager
  • interface to (controls) all hardware & software, files and environment
  • controls and coordinates all processes (running programs)
  • manages access controls (file permissions or device access)
• Intro to the UNIX Operating System, a lecture (16 mins) http://youtu.be/N-JDrglL8es
• AT&T Archives: The UNIX Operating System (28 mins) - Old (1982), but good intro to software development, UNIX and C. Hear it from Thompson & Ritchie! - http://youtu.be/tc4ROCJYbm0

History

• Originally, OS was developed for a particular machine (and written in assembler, see below)
• Released for "free", Berkeley redesigns and also releases it
• Multiple versions created by various companies
• UNIX become a major part of the growing Internet (ARPANET) with TCP/IP
• X-Windows allows UNIX to join the GUI world - more accessible to average users
• POSIX standard developed to unify the various versions
• Linux made available free
• 1975 Unix - Bell Labs
• BSD - Berkeley
• Other versions
• 1983 - GNU
• 1991 - Linus Torvald
• Portable
• Free
• Not proprietary
• Uses C programming language
  Ken thompson, 1969, AT&T Bell Labs

Overview

• Multi-user
• Multi-Tasking
• Utilities such as sort
• Different Shells (Command Interpreter and Programming Language) - bourne, Bash, Korn, csh. You talk to the shell, which talks to the OS, which sends responses to the shell, which shows you
• Kernel system calls, e.g., write
• Hierarchical File Structure - treelike, links
• Security for private and shared files
• Filename generation using patterns (bourne has more)
• Device independent I/O
• Job Control - ps, jobs, fg, bg, &
• Filters (Interprocess Communication)
• GUI
• Networking - e-mail, httpd, ftpd, ...

Terminal

• GUI (KDE, Gnome)
• termial is a connection into obisidian
• type in commands
• Uses the power of your workstation to emulate a graphical terminal
• Local machine has own file system
• a terminal connection( Old school) With a few exceptions, you are running a program that pretends it is one of those ancient (fairly dumb) terminals shown in the AT&T video
• You type a character (ASCII), it gets sent to the UNIX server (and is echoed back to your terminal)
• When you press the enter key, the shell interprets the line of input as a command Or, if you are running some other program that accepts input, the line is passed to that program instead

Logging in and out

• putty to obsidian.sru.edu
• login with campus id and password
• The shell splits the command line into its component parts
• The actual command - either built-in or the name of a file that contains the program
• Wildcard characters - pattern matching - that are replaced by whatever they mean (for example: *.c)
• Arguments or flags that modify something about the command. These are passed along to the program which interprets them as it sees fit
• Redirections. Normally the input and output are connected to your terminal, but we can ask that one or the other be a file or another process (program)
• Logging out
  • [Ctrl-d] - also sometimes written ^d - which means I have no more input for you
  • logout - an internal command that tells the shell process to quit running
  • exit - same as logout
  • Or, dismiss the Putty session

System Administrator

• A privileged user. Originally, just "root" or the "super user".
• Has access to everything on the system and is responsible for set up (configuration) and maintenance
• If you are running your own system, you are the sysadmin

Software Architecture

• Usually depicted as concentric layers
• Hardware
• Kernel always in memory, this is the heart of the OS
• Utility programs (sometimes considered part of the OS) and various shell programs
• Applications and user programs
• End user who communicates with a shell or one of the applications or user programs

Files & File System

• OS maintains the hierarchical file system
• Files include systems files (config), programs, user programs, even devices
• An added disk drive just becomes part of the hierarchical file system
• All files have permissions (access control) associated with them

Processes

• Any program that is running is a process
• We can both run bash, but we each have our own bash process
• Process inherit access control properties from the user - the OS handles temporary changes to allow you to, for example, access a disk drive
• Processes may end when their job is done, or may be "killed"

Unix Features

• True multiuser system, unlike Windows or Mac OS
• Multitasking - other users, windowed GUI, you can even multitask on terminal connection
• We'll get to this later, but you can also have multiple terminal connections; just start Putty again
• Applications and tools - constantly changing, see http://en.wikipedia.org/wiki/Unix_shell for a list of shells
• Building-Block Approach - do one thing well
• Leads to programs that run silently; no extraneous output, including headers
• Pattern Matching

Documentation

• man unixCmd - basic manual entry
• info unixCmd - sometimes more information from the documentation
• man -k someKeyWord show all the man pages containing that keyword
• whereis unixCmd

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  All work herein is subject to copyright. Original content to Dr. Deborah Whitfield, text content (Your Unix/Linux) to Prentice Hall publishing.