Introduction to Linux, Emacs, and Firefox

The Login Process:

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 graphical menu asking which operating system to load. Use the down arrow key 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:

• Type your user name and press Enter.
• Type your password (the same password you use to access myRC and email) and press Enter.

If you have problems logging in, make sure that you are entering the correct user name and password. 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 part of the file system you will be using has been mounted from Linux servers (that is, you will be storing your files and using programs on the Linux servers). You should see a desktop environment similar to Windows. This is GNOME, one of the most popular desktop environments for Linux. A separate window management program is running in conjunction with GNOME but we will loosely refer to everything in the windowing environment as GNOME. Here are some 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 clicking on the FOOT icon at the left end of the Panel (the Applications option), then choosing options from the menus. 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. To the left of this bar is a small box with four rectangles that represents your desktop. GNOME lets you manage multiple desktops. By default there are four.
• The panel can be customized by adding and deleting icons and moving them around. For example, to remove an icon from the panel, right click on the icon then choose "Remove from Panel."
• In this course we will use X-terminal windows (for typing in shell commands) and Emacs (for typing in programs) extensively so we need icons for these on the panel. Add an icon for emacs to the panel by clicking on the FOOT, then choosing Accessories. Right click on emacs and choose "Add this launcher to panel." To add an icon for a terminal window click on the foot, then choose System Tools, then choose Terminal (there is a possibility these aren't on the menu - if not, don't worry about it).
• Launch an X-terminal window (an xterm) either by clicking the icon on your panel or by right clicking on the desktop then choose Terminal. You should note that the window has nothing in it except the prompt which shows you the full pathname of the directory you are in (your present working directory). Shell commands are typed in an xterm at the prompt -- more on shell commands later. Leave the xterm open -- we'll come back to it soon.

Managing GNOME Windows

The windows you will use under GNOME will feel much like those under Windows 98, 2000, NT, or XP although a few things are different. Click on the xterm (terminal) 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. For example, later in the course 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. Or, you may want to have your browser open in one workspace, the emacs editor in another, or whatever. 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 rectangle.

Moving Around the Linux File System

Now that you can get around the window environment, let's take a look at an xterm. Click on one of the terminal windows to activate it. The program running in the xterm is called the shell. The shell lets you issue commands 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.
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 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 “projects”.    We will use this directory later in the term.
  
  

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.

Emacs

Editing an existing file

We'll first use Emacs to edit the UnixQuestions file. To open this file in your lab0 subdirectory do the following:

• In your Emacs window, use the pull down menu item Open File... under the Files menu, or use the key stroke C-x C-f   (the C stands for the Control ctrl key -- hold it down then press the x key, release the x then press the f).
• Look at the bottom of the window in the minibuffer and you will see the words Find File: followed by the path of the directory you were in when you started Emacs (probably "~/", that is, your home directory). You need to specify the path for the file you want to open to edit. If you have correctly created your subdirectories, the file should be in ~/cs120/labs/lab0/UnixQuestions. (Remember that this is the same as /home/students/yourUsername/cs120/labs/lab0/UnixQuestions because ~ stands for your home directory.) Type this into the minibuffer (don't type the ~/ again if it's already there) and press ENTER and you'll be in a buffer containing the file. The file name corresponding to the buffer will appear near the bottom of the window on the status line.

A useful Emacs command: If you ever get stuck halfway into an Emacs command, where the minibuffer is asking for something that you don't understand, type C-g (hold down the ctrl key then hit the g key). This aborts the current command.

Now go to the top of the document and type in your name, then type in the answer to each question immediately following the question.

Save the file by typing C-x C-s (hold down the ctrl key then hit the x key, then release the x key while still holding the ctrl key and hit the s key) OR choose File, then Save (current buffer) from the menu.

Activate the shell window and 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~ (you may have another one #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). If you see #UnixQuestions# in your list then you must have closed the file in some abnormal way without saving (for example, if the power went off this would be an emergency backup created by the system).

Now use the nenscript command to print out your answers. The command is as follows:

This tells it to print file UnixQuestions to the lab printer.

Firefox

Firefox is an open-source web browser that looks and acts much like Netscape or Internet Explorer. Open Firefox by clicking on the globe icon on the panel. First, if the Roanoke College page did not come up as the default page (probably the Ubuntu home page showed up), change the settings as follows. Select Edit from the menubar, and then click Preferences. The preferences window will open, and on the right you should see a textbox for Home Page. Type in www.roanoke.edu and click OK. Clicking the Home button in the main browser window should now take you to the Roanoke home page. Now type the following URL (be sure to use the right one for your class) into the Location box:

http://cs.roanoke.edu/Fall2006/CPSC120A (Dr. Ingram's class)

                      or

http://cs.roanoke.edu/Fall2006/CPSC120B (Dr. Hughes' class)

Look over the page; note that it contains links to the syllabus, to various useful information, and to the programs (none yet) and labs. Click on the lab 0 link and you'll see the online version of this document. Most labs will contain links that you need to follow, so in general you will use the online version.

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) 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 UnixQuestions in the Subject line. Click Attachments, then Browse, and find your UnixQuestions file -- this is a graphical view of the file system, so double-click the folders to open them. 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. To return to the message composition screen, click Go Back to Message. You should see your filename next to Attachments. Now, send the e-mail. After each lab you will e-mail your work to your instructor.

Close Emacs and Firefox.

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.)