Lab 0: Introduction to Linux and Firefox

Getting started with Linux:

The computers in the 2nd floor MCSP lab are dual boot, capable of running Windows XP or Ubuntu Linux, an open source version of Linux. Generally you will find them running XP so you will need to reboot into Linux as follows:

• Press CTRL-ALT-DELETE, choose to ShutDown, then select Restart from the pull down menu.
• Watch the screen! It does a few things and then displays the bootloader screen (LILO), with a menu asking which operating system to load. Use the arrow keys to highlight Linux, then press ENTER. (If you wait too long, Windows XP will automatically be loaded!)

After Linux has been loaded you should get a login screen. To log in, enter your username and password (the same that you use to access myRC and email) and press Enter. If you ever have password problems, go to Information Technology on 3rd floor Trexler for assistance. You are now logged into the local machine, but you will be storing your files and running programs from a remote computer (named "CS"). This means that you can use any computer in the lab and still be able to access your personal files.

You should see a desktop environment similar to Windows. This is GNOME,it is responsible for providing a graphical, desktop interface for Linux. Here are some of the basics for getting around in Gnome.

• The bar across the top of the screen is the GNOME Panel. Just as you access programs in Windows from the Start menu, you can access programs in GNOME by selecting the appropriate menu options on the GNOME Panel. You should also see three icons on the panel - one for the Firefox Web browser, one for the mail program Evolution, and one for GNOME Help. You can hold your mouse over an icon to get information about it.
• A taskbar is at the bottom of the screen. It contains an icon for each window that you have open on the desktop. These are similar to the icons that you see on the taskbar in Windows.

The GNOME panel can be customized by adding and deleting icons and moving them around. In this course we will regularly use three applications: X-terminal windows (for typing in shell commands) Eclipse (for writing programs) and a Text Editor (for providing answers to lab activities). It would be helpful to add icons for these on the panel.

• Add an icon for an X-terminal to the panel by clicking on the "Applications" option, then choosing Accessories. Right click on terminal and choose "Add this launcher to panel."


• A similar process can be used to add an icon for the Text Editor.


• Finally add an icon for Eclipse (it is found in the "Programming" section of the Applications menu).


• If you ever wish to remove an icon from the panel, right click on the icon then choose "Remove from Panel."

The windows you will use under GNOME will feel much like those under Windows XP. However, there are a couple of tips that you should be aware of. Click on the xterm icon on the Panel to get another xterm window, then use your two windows to get comfortable with these basics:

Moving Windows: As usual, windows can be moved by clicking on the title bar and dragging the window with the mouse. Alternatively, you can hold down ALT and then click anywhere in the window to drag it to a new location. This is particularly handy if the title bar is not visible.

Activating a Window: The window that has a brown title bar is the active window. Only one window can be active at a time. To make another window active, click inside that window or on its titlebar. This will both activate the window and bring it to the front. When you have more than one window open it is often helpful to cycle through them to get to the one you want to work in. The usual way to cycle through windows in GNOME is by pressing Alt-Tab (hold Alt down, then press Tab), just as in Windows XP. Now try ALT-Tab; it should cycle through the windows.

Using Multiple Workspaces: GNOME allows you to have several different workspaces open simultaneously. This is something that you have probably not experienced with a Windows interface. This feature can be useful in grouping together windows that are supporting different tasks. For example, you may want to have one workspace with a terminal window where you are working on your personal web pages and another workspace with a terminal window to work on lab exercises. Alternatively, you may want to have a full-screen browser open in one workspace and Eclipse in another. The GNOME panel shows your workspaces (a grid of 4 rectangles in the right hand corner of the taskbar -- in each rectangle smaller rectangles indicate windows open in that workspace). At this point you should have one workspace open with a window open in it. To change workspaces, just click on the corresponding rectangle.

Using the Command Line Interface

Windowing environments provide a graphical interface to the computer that leverages the strengths of the human perceptual system. We can easily locate and manipulate symbolic representations of our data by using the mouse to point, click and drag. While this kind of operation is highly intuitive, it is not always the most efficient. For this reason, it is sometimes beneficial to interact with the computer system by using descriptive commands that explicitly tell the machine what to do. The command-line interface for Linux systems is accessed through an X-terminal(xterm).

You should already have two xterms open; click on one of the windows to activate it. The program running in the xterm is called the shell. The shell lets you issue commands explicilty to the Linux operating system and work with files. Refer to the Linux Command Reference and Linux/Unix Overview handouts given in class as you answer the following questions and type in the appropriate commands to move around the file system. Pay attention to what happens on the screen after each command.

• Where are you in the file system when you login?
  
You can find out by typing in the command to show your present working directory. What is the command (look on the Linux command summary to find out)? _____________

What is displayed when you type in the command (and press ENTER)?

___________________________________________________
(Note - this should be the full pathname of your home directory.)



• Let’s go to the root directory (also known as “/”).
  
To change directories you need to type the command cd (for change directory) PLUS you must also type in an argument specifying the directory you want to change to (give either an absolute or relative path to the directory). Note that for any Linux command with an argument you must type a space between the command and the argument. So in this case you need to type


                cd  /



• Look at the files that are in the root directory using the ls command.   Notice that some are displayed in dark blue while others are displayed in light blue.   What is the difference?
  

To confirm your hypothesis, you might try typing ls -l (that is an el for long, not a one) to get a long listing of the files.    This shows you the permissions on each file (described on the last page of the Linux/Unix Overview), the ownership of the file (most of these are root), the size of the file, and the date of last modification of the file. Make a careful note about the permissions that you see there.




• Change directories to the “bin” directory, (bin is a subdirectory of root – you should see it in the list from the last step - that means you can change with the command cd bin) and then list the files.   Note that a lot of the files contained in this directory are displayed in green.   You may also notice some familiar file names (cp, ls, pwd, for example).   What do these (green) files all have in common?    Can you confirm you hypothesis using ls –l?
   
  
• Let's look at the permissions and other information for a specific file, the cp file. To do this we need to add the filename as an argument to the ls command as follows:

                ls -l cp
  

  Make a note of what happens (especially the permissions).

• Now we want to go back to your home directory.   From here, there are several ways that you could do that.
  
  
  • cd ../home/students/username takes into account your current location.  Effectively this will take you back up one directory, and then down through home/students
  
  
  • cd /home/students/username specifies the absolute path that you want to jump to
  
  
  • Since you are going to the home directory of a user, you can just type cd ~username
  (of course put your username here)
  
  • Better yet, since it is your home directory, you can just type cd
  
  
• Verify that all of these commands have the same result.

Setting Up Your Directory

Now we'll set up your directory with some subdirectories and copy some files into them. Do the following:

• Confirm that your directory is empty except for one file named “Desktop”


• … or is it?   Some files are not always displayed (because you don’t need them all on a regular basis). How do you list all of the files in your directory? (Look at the Linux Command Reference)
  
Notice that all the “hidden” files start with a “.” – these are created by the system



• You need to create a new subdirectory, named cs120, to store your files for this class. Look at the command reference to figure out the command to do this. Please note!!! Linux is case-sensitive; the directory cs120 is different than CS120. It is very important in this class that you type in commands, pathnames and filenames in the correct case!
  Confirm that it was created successfully -  how do you do that?
  
  
• Change directories to the new subdirectory and confirm that you are there.
You can use pwd to confirm, but you may also notice that your current directory is also displayed as part of your prompt.


• Create a new subdirectory called Labs (Note the capital 'L') and change to this directory


• Create a new subdirectory called lab0 and again change to this directory


• Now we want to copy a file called UnixQuestions from the cpsc home directory to your present directory. Some things to consider in figuring out the command:
  
  • The command is cp (for copy) but you must supply two arguments - one the file you are copying and the other telling the operating system where to put the copy. The syntax for copying files is
  cp originalFile newFile     or   cp originalFile newDirectory
  

  (see the examples in the Linux Command Reference)

  • The pathname for the original file is ~cpsc/UnixQuestions (Note: cpsc is a username used by the department so ~cpsc specifies its "home" directory.)
    
    
  • The new directory is the one you are currently in. Remember that you can refer to your current location as “.” - that is, a single dot.
  
  
• When you have the file (confirm with ls), use the more command to display this file on the screen.


• Go back to the cs120 directory by going up the tree (remember the directory up one level is referred to using two dots so changing up one level is cd ..). You should have only one subdirectory of cs120 at this point (Labs).   Create another subdirectory called Assignments (Capital 'A'!).     We will use this directory later in the term.
  
  
• We need to get one more file for today's lab. In the cpsc home directory there is a file named "RCEclipsePrefs.epf". You need to copy that file to your home directory.

STOP!!! Before going further have the instructor or a lab assistant come over and check to see that you have your directory set up correctly. You will be asked to go to your home directory, show a listing of the files there, then go down into the subdirectories you have created and show what is there.

Using the Text Editor:

Editing an existing file

Open the UnixQuestions file using the appropriate menus, icons or keystrokes. Notice that the directories that you created using the command line interface are shown here as folders. Remember that the file you are looking for is in the path: ~/cs120/Labs/lab0 Now, you are ready to edit. As in a word processor you may move around in the buffer with the arrow keys and with the mouse.

First, go to the top of the document and type in your name, then type in the answer to each question immediately following the question. Notice that as soon as you make any change to the document that the filname (both on the window titlebar and in the taskbar) is preceeded by an asterisk (*). This is an indication that you have changed the document but have not saved your work. You should always save your work periodically!

When you finish answering all the questions, save your work and activate the shell window. Use the ls command to list the files in your lab0 directory. You should notice that you have at least two: one is UnixQuestions and the other is UnixQuestions~. The one named UnixQuestions is your most recently saved version of the file; the one with the ~ at the end is an older version of the file (if you only saved once it is the original file that had the questions with no answers).

To print out your answers, use the nenscript command as follows:

This tells it to print file UnixQuestions to the lab printer. The additional parameters to the print command tell the printer how you would like the document formatted. Specifically, you are asking for 2 columns, rotated to landscape orientation and add a Gaudy title.

Firefox

Firefox is an open-source web browser that looks and acts much like Internet Explorer, Safari or Netscape. Open Firefox by clicking on the icon on the panel. First, we want to set the class webpage to be your homepage. Under the Edit menu, select Preferences. The preferences dialog will open, and on the right you should see a textbox for Home Page.

If you are in Dr Ingram's class, type in:

http://cs.roanoke.edu/Fall2007/CPSC120A 

http://cs.roanoke.edu/Fall2007/CPSC120B 

Now go to myrc (http://myrc.roanoke.edu), log in, and go to the Outlook tab. (Alternately: You can go straight to Outlook without going to myRC by going to http://owa.roanoke.edu) Bookmark this link - you will use it every lab to submit your work via e-mail.

1. Click on the new button in the upper-left hand corner, and address the message to your instructor (hughes@roanoke.edu or ingram@roanoke.edu). Put Lab0 in the subject line.
2. Click Attachments, then Browse, and find your UnixQuestions file When you have located the file (remember to choose the one named UnixQuestions NOT UnixQuestions~), click Open and then Attach. The filename should now be under Current file attachments.


3. You also need to send the code for your program. It should be contained in a file called "Hello.java". Remember that it was contained in the package lab0 - you should have enough information to know where it is located in the file system. Once you have found it, make sure to attach this file as well.


4. To return to the message composition screen, click Go Back to Message. You should see your filenames next to Attachments. Now, send the e-mail.

Exiting an X-terminal: To exit an xterm, type exit at the command prompt.

Exiting GNOME

To exit GNOME, click on the System option on the panel and choose Log Out. In the next window, select the "Reboot" option if you are through using Linux. The computer will then automatically reboot Windows XP. (If you click the "logout" option the computer will go back to the Linux login screen.)