Introduction to UNIX

IEEE Pizza-Talk Series --- October 8, 2004

Dr. Nickels

UNIX? What's UNIX?

An operating system (an OS) is the computer program that orchestrates all other programs.... gives and takes back control from applications, manages files, etc.)
UNIX is really a set of similarly-designed OSs, including Solaris (Sun's OS), HP-UX (HP's OS), Linux (Including RedHat, Gentoo, Debian, SUSE, etc.), FreeBSD, IRIX (SGI's OS), and more.
Some syntax changes (is it "ls -l" or "ls-l"?) from system to system, but the basics are the same.

Advocacy --- Why UNIX?

In General
- Scalability (web farms)
- Remote Management (labs)
- Stability (web servers, e-commerce)
- Security (e-commerce)
- Quotas (labs, ISPs)
- Cost of Ownership (everyone!)
For a desktop system
1. No Drive Letters!
2. No "BSOD"
3. Reboots? What reboots?
4. Virii
5. Customization, Customization, Customization!
6. Remote execution
7. Native Postscript
General Philosophy
1. a specialized program for every task
2. the windowing system itself is a bunch of application programs... not part of the OS!
3. different editor, spell-checker, typesetter, previewer, printer programs --- often different choices for each, "it's the users choice!"
4. modern exceptions: netscape (though Mozilla has since broken into multiple applications!), OpenOffice

Shells

What is a shell/terminal window?
- Terminal window - graphical window running a text "shell"
- shell: text-based interaction with system.
- A bit of history: Before windowing systems, a shell was the user's only interaction with system (via a dumb-terminal, hence the "terminal window" or "terminal emulator" moniker). Now, systems let you interact in several ways at once.
- Several different shells out there, differing mostly in syntax (setting variables, writing scripts, etc):
  - sh - the orginal shell (bourne shell)
  - csh - syntax similar to the C programming language
  - tcsh - extensions to csh - default for us
  - bash - bourne again shell - extensions to sh
What can I do with one?
- Lauch new text-based programs
  - cd Networks
  - man ls
  - less .tcshrc
  - spice3
- Lauch new graphical programs.
  - dtpad .tcshrc &
  - matlab &
  - background/foreground and "&"
    - If you just launch a program, it runs in place of the shell on the processor.
    - If you put an & as the last character of the command, the new program will istead detatch itself from the shell, and return the shell to user interaction. This is called running something "in the background" and takes advantage of multitasking.
    - To recover your shell after launching a program (without the &), type ^Z (hold down CNTRL and Hit Z), then type bg.
    - To see what background jobs a shell is currently running, type jobs.
    - To move a job from the background to the foreground, type fg.
How do I start a terminal window/shell? CDE -- Right-click on background, choose Hosts/This Host CDE -- Go to "cpu/disk meter menu", choose This Host GNOME -- Click the icon on the top button bar. GNOME -- Go to Menu, then.... from a shell -- dtterm &" from a shell -- gnome-terminal &" from a PC -- From the Windows Menu, Choose Run then type "telnet <host>" (e.g. telnet joule.engr.trinity.edu) from a PC -- Use a graphical SSH program to connect (to joule from off-campus, to any sun from on-campus). My favorite is PuTTY, but a list of available windows ssh programs can be found at http://www.openssh.com/windows.html


	   How do I close a shell?

		    
		     exit; logout
		    double-click left-top button
		    
				
		Hints and Tips
		    
		    arrow keys and editing previous commands
		    tab completion and ^D listing


		

 Files and Directories on UNIX
      
		 Useful commands 
		     
			  Command Format -- command [options] [arguments] 
			         
						Syntax note:[] means optional 
						       parameter 
						Syntax note:<> means required 
								 parameter 
			         options often start with -, only one
						- is required (e.g. ls -alF)
						
			  Directory Navigation & Control 
			      
					cd [DIRECTORY/PATH] -- change directory
					(goes to home directory without argument) 
					mkdir <DIRECTORY> -- make new directory
			      rmdir <DIRECTORY> -- remove (empty) directory
					ls [DIRECTORY] -- list current or named
				      	directory  
					ls -a  -- list all files (files that begin
							with the character . are normally
							hidden). 
			      ls -l  -- long listing 
			      ls -F  -- put a special character beside
					    non-normal files (/ for directories, * for executable files,
					    @ for symbolic links, etc).  
				   
			    File Maintenance 
					
			      rm <file> -- remove file
			      less <file> -- examine file; <sp> to cont;
			                q to quit
					cp <file> <file2 or directory> -- copy file
					mv <file> <file2 or directory> -- move file
					lpr <file> -- print file (only
					do this with text or postscript files (NOT PDF/Graphics!!)
					
 
			    Help
					
					man <command> -- view help text about
					    <command>; <sp> to continue; q to quit
					man -k <keyword> -- what commands involve
					    <keyword>??
					
 
		     
				
		 Interesting Directories 
		     
			   /tmp  --  temporary directory, read/write by
			  anyone.  Gets cleaned on every boot-up!
			   /home/user  -- home directory.
			  Read/write by only you. 
			   /home/linuxhome/user  (on Suns) -- linux home directory.
			  Your linux home directory, when on the Suns. 
			   /rexhome/user  (on Linux) -- sun home directory.
			  Your sun home directory, when on the Linux machines. 
			   X:  (on ITS PCs) -- sun home directory.
			  Your sun home directory, when on ITS PCs. 
			   /home/user/public_html -- We are running a web
			  server for you!  -- files in this directory
			  (one the Suns) can be accessed through
			  http://www.engr.trinity.edu/~user
			   /NetHood -- (If you are running
			  Sharity&) this maps to the Windows "Network
			  Neighboorhood".  Therefore, to access your Y: drive from unix,
			  type cd /NetHood/TUCC-TIGER/Users/username
			  (entering your ITS password!)
			   . -- shorthand for the current directory.
			   .. -- shorthand for the parent directory.
			   ~ -- shorthand for your home directory.
		     
				
		 Interesting Files 
		     
			    /home/user/public_html/index.html -- the default
			  file that someone sees if they access 
			      http://www.engr.trinity.edu/~user
			   core  -- system file generated when a program
			  crashes.  You may safely delete any and all of these.
			   Hidden Files - any file starting with a period (.) is
			  normally hidden.
			  
 .bashrc  -- configuration for bash 
			    .forward  -- where to forward your email (see
			  below)
		     
				
		
		

 E-mail forwarding
		
		 ALTERNATIVE: We also run a POP3 server on rex.engr.trinity.edu,
			  so you can configure some email clients (the program that you
			  run on your machine) to just grab it from there instead of
			  forwarding.  
		 WARNING! If you create a loop (account A forwards to B,
			  which forwards to A, ...) you will lose email and possibly
			  create problems on both systems.
		 To forward from the exchange server to another server (for
      		example, the engineering server, rex.engr.trinity.edu):
				--- You have to call or email the helpdesk
				(helpdesk@trinity.edu, x7409).  Microsoft (or ITS, I don't
				know) doesn't allow users to do this: maybe it'll be in the
				next version :)
		
 To forward from your engineering account to your exchange
			  account, or any other account --- Edit a text file called
			  .forward in your home directory. This file should
			  contain one line, the email address to which you wish your email
			  sent.  
      

Some (other) good sources of information 
		    
			  Dr. Nickels' HOWTO page 
					 
					 http://www.engr.trinity.edu/~knickels/howto
			 
 Notes from UNIX short course at Ohio State: available at
		         
				   http://wks.uts.ohio-state.edu/unix_course/unix.html
			  A Beginners Guide to UNIX, by Matt Chapman & Frankie
			      Blaskovic: available at 
			      
			      http://www.belgarath.nildram.co.uk/guide/all.html
			      
					 Local ENGR Page
			 
			 

Prev: Gnome  
  
  
Next: Local Applications