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1 Introducing UNIX

1 Introducing UNIX. What is UNIX ? UNIX Kernel UNIX Shell Example Commands UNIX Filestore - next lecture. What is UNIX?. UNIX is an operating system An operating system is the program that controls all the resources of a computer system - both the hardware and the software

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1 Introducing UNIX

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  1. 1 Introducing UNIX • What is UNIX ? • UNIX Kernel • UNIX Shell • Example Commands • UNIX Filestore - next lecture

  2. What is UNIX? • UNIX is an operating system • An operating system is the program that controls all the resources of a computer system - both the hardware and the software • Most importantly, it allows you to make use of the facilities provided by the system. Every computer has an operating system.

  3. Different Flavours of UNIX • Commercial: Sun Solaris, SCO, IRIX • Open source: Linux, FreeBSD, NetBSD • Lots distributions • Cygwin • Not a full OS but an implementation of all the standard tools and system calls of UNIX • MacOS X • Underlying operating system is BSD

  4. Parts of the UNIX System

  5. UNIX Kernel • At the core of each UNIX system (and most operating systems) • Loaded in whenever the system is started up • Manages the entire resources of the system, presenting them to you and every other user as a coherent system • You do not need to know about it in order to use a UNIX system, but very important if you are administering one.

  6. UNIX Kernel (2) • Amongst the functions performed by the kernel are: • managing the machine's memory and allocating it to each process. • scheduling the work done by the CPU so that the work of each user is carried out as efficiently as possible. • organising the transfer of data from one part of the machine to another. • enforcing the access permissions that are set on the file system

  7. UNIX Shell • The UNIX command line interface is called the ‘shell’ • The shell is a program interpreter • There are many different shells, for example csh, bash, sh. • Usually you will run only one type of shell in a login session

  8. What is a Command Line Interface? • In Windows you usually do things by selecting something with the mouse and then clicking (GUI), but there is limited command line support • In UNIX, traditionally, you do things by typing in commands, but GUIs are common nowadays. • The Diving Bell and the Butterfly

  9. Command Line Completion • Very useful although not always available (available in bash!) • Start typing command (or file name) and then press tab • The shell will try to automatically finish the word for you • If more than one choice, press tab again and the shell will list the possibilities

  10. Copying and Pasting • In Windows you cut and paste using items in the Edit menu • In UNIX you can also use your mouse • Left button (click and drag) to highlight the text you want to copy • Middle button (click) to paste the text somewhere else

  11. A Shell Window

  12. Accessing your Linux account • Use NoMachine • For more info, read document by Paul Dempster (see U drive) • It’s a client-server system, with a twist

  13. X-Windows • In a normal client-server system (for example, an email system) the software on the local host is the client and the software on the remote host is the server. • In a X-Windows system this is reversed. • The X-Windows server is on your local machine. It provides the following services: keyboard input, mouse, procedures for drawing on the screen, etc. • The clients are on the remote host. Client processes running on the remote machine use your X Server to get the input from your keyboard and mouse and to display their output on your screen.

  14. Opening and closing the terminal • To open the terminal: • You can close it by typing exit or pressing ^D (Ctrl+D)

  15. Shell vs. GUI • Advantages of command line interfaces vs graphical interfaces: • Easy to automate • History of commands • More productive (once you know what you are doing) • Works well over slow network connections • Disadvantages: • More difficult at first (but you get used to it)

  16. Linux at Home • The University’s Linux server is only accessible from within the campus • You might want to try installing Linux on your own PC, but this might not be trivial • A simpler option is to download a “live” distribution (a bootable CD)

  17. UNIX Commands • Shells perform user requests and they do this by accepting commands • Different types of shell have different commands, although the core commands are common • A command consists of one or more words separated by white space • The first word is the command name • Subsequent words (flags and arguments) give additional information or modify the command • E.g. ls –l /usr

  18. Command Entry • A command is only entered when you press the ENTER (or RETURN) key • Special key strokes include: • DELETE or back space to delete the last character (also ^H) • ^D to delete the next character • ^W to delete the last word • Alt+U to delete the entire line • ^C to kill most commands • ^A and ^E to go to the beginning or end of the line (^X means press the Control key and X at the same time)

  19. Example UNIX Commands • who • date • finger • passwd

  20. Example UNIX commands (2) • The who command displays a list of current users on the system • Information includes usernames, where they are logged in from and when they logged on zlizmj pts/7 Mar 5 10:49 zuczpd pts/8 Mar 5 11:20 zlizmj pts/9 Mar 5 11:20 zliybzd pts/10 Jan 2 09:03 zliybzh4 pts/12 Jan 8 12:32 zliychj2 pts/13 Jan 7 13:50 zliyblj5 pts/19 Jan 26 15:46 zlizjc pts/22 Jan 3 14:45 (unix:1031.0) zuczpd pts/15 Jan 3 12:06 (mb-gx520-030.nottingham.edu.cn)

  21. Example UNIX commands (3) • The date command displays the current date and time: Mon Oct 9 11:27:07 BST 2000 • finger describes the person behind a username, for example, finger gmh@marian gives: Login name: gmh In real life: Graham M Hutton Directory: /staff/gmh Shell: /bin/csh Last login Thu Sep 16, 1999 on pts/2 from marian No unread mail Plan:

  22. Example UNIX Commands -Changing your password • The passwd command changes your password • This is one of the first things that you should do • You are prompted for the old and new passwords (the new one twice) • You cannot change your password from the CS Linux server (passwords are stored on a Windows server)

  23. Other Useful UNIX Commands • man - manual pages • info - more extensive documentation • gpdf - viewer for PDF files • ggv - viewer for postscript files • konqueror - web browser and shared folders browser • bzip2 - compress a file (reverse bunzip2)

  24. Summary • Introduction to UNIX • UNIX Kernel • UNIX Shell • Basic UNIX commands • Next Lecture: UNIX Filestore

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