Introduction to Statistics (MAT/SST 115.03 2008S)

Laboratory: Getting Started with Linux


Summary: This laboratory reviews some mechanics related to the use of the Computer Science Linux Network for MAT/SST 115 Specifically, this lab gives you the opportunity to explore:

Please don't be intimidated! Although this lab contains many details which may seem overwhelming at first, these mechanics will become familiar rather quickly. Feel free to talk to the instructor or with a Linux User Consultant if you have questions or want additional help!

Background

As this is a workshop-style course (aka “a constructivist, collaborative computing course”), you will be working on the computers in our classroom on most class days. You will quickly find that these computers have many similarities to the computers you have used in the past, but that there are also some differences. (When we started teaching this course, many students hadn't used computers at all. You will occasionally find comments in the readings and labs that reflect that different perspective.) In this lab, we will explore some of the key issues you may need to consider in working on the Linux computers that we use in this class.

In Grinnell's computer science department, we use an operating system known as Linux. Linux is distinguished by being an Open operating system (which means that anyone who has the knowledge and desire to make modifications to the program code of the operating system is permitted to do so) and a Free operating system (which means that it doesn't have to cost you anything to install it on your computer, unlike the Macintosh OS, with a list price of about $150, or the Windows OS, with a list price of about $400). Admittedly, the Linux community uses “Free” in two ways, in the way we used it above (as in “Free Beer”) and in the way we used “Open” (as in “Freedom”).

Because we'll be using Linux, you'll need to spend a bit of time getting used to the system. Today's lab will give you an opportunity to do so. You and your lab partner should each go through all of the steps of the lab, each person using her or his own account.

Logging In

Short Version

  • On the computer in front of you, you should see a small window that asks you to log in. If you don't see such a window, try hitting a key on the keyboard or clicking the power button on the monitor.
  • Enter your user name. Press the Enter key.
  • Enter your password (which won't appear). Press the Enter key.
  • Get help if those previous two steps don't work.

Detailed Version

To use any of the computers on Grinnell's Linux network, one must log in, identifying oneself by giving a user name and a password. You will have received a Linux user name and password from the instructor if you did not already have one. If you have not received a Linux user name and password, or if you have forgotten either one, please tell your instructor.

When a Linux workstation is not in use, it will display a login screen with a space into which one can type one's user name and, later, one's password. (If the workstation's monitor is dark, move the mouse a bit and the login screen will appear.) To begin, move the mouse onto any part of the box containing the login box. Type in your user name, in lower-case letters, and press the Enter key. The login screen will be redrawn to acknowledge your user name and to ask for your password; type it into the space provided and press Enter. (Because no one else should see your password, it is not displayed on screen as you type it in.)

At this point, a computer program that is running on the workstation consults a table of valid user names and passwords. If it does not find the particular combination that you have supplied, it prints a brief message saying that the attempt to log in was unsuccessful and then returns to the login screen -- inviting you to try again. Consult the instructor or the system administrator if your attempts to log in are still unsuccessful.

The Linux/Gnome Window Environment

Short Version

  • You'll see something that looks somewhat like Microsoft Windows, but also somewhat different.
  • Icons at the bottom of the screen can be used to start programs.

Detailed Version

Once you have logged in, a control panel will appear at the bottom of the screen. Some other windows also may be visible in other parts of your screen. All of these areas are managed by a special program, called a windowing system. On our network, login chores and other administrivia are handled by a program or operating system, called Linux, and the primary user interaction is handled by a windowing system, called Gnome.

Practice with a Terminal Window: Changing Your Password

Short Version

  • Click on the picture of the small computer monitor. A new window, called the Terminal, will appear.
  • Type yppasswd and hit the Enter key to change your password. You will be prompted for your old password and your new password. (The letters you type will not appear.)
  • Type exit and then hit the Enter key to close the window.

Detailed Version

While we can run several programs directly, we will need to invoke others by name. The computer program that reads and responds to such invocations is called the shell, and your interactions with the shell takes place in a window generated by a program called a terminal emulator, or terminal for short.

You may already have a Terminal window on screen. If not, you can start one at any time by moving the pointer onto the small monitor icon at the bottom middle of the front panel, and clicking with the left mouse button. Shortly a window appears, displaying the shell prompt -- the name of the workstation on which the shell is running, followed by a percentage sign. This prompt indicates that the shell is ready to receive instructions.

You type in such instructions using the keyboard. Move the mouse pointer into the Terminal window and click the left mouse button to make the window active. Notice that the window frame changes color following the click, indicating that the window has become active.

To get rid of the Terminal window, press Ctrl/D. That is, hold down either of the keys marked Ctrl, just below the Shift keys, and simultaneously press the D key. (On our workstations' keyboards, the keys marked Ctrl (“control”) and Alt (“alt” or “meta”) are somewhat like Shift keys, in the sense that they modify the effect of other keys that are pressed simultaneously.) The shell program interprets Ctrl/D as a signal that you have no more instructions for it and halts, and the terminal emulator closes the window automatically once the shell stops running. Alternatively, you may close a window by moving the mouse to the x at the top-right of the window, and clicking the left mouse button. Finally, you can usually type exit to close a terminal window.

It is a good idea to change the password associated with your account shortly after you receive it and every few months thereafter. The program that one uses to change one's password is by its name, “yppasswd”.

Choose a new password. Make it something that you can easily remember, but not an English word or a name, since it is easy for system crackers to break in by guessing your password if you choose it from one of those categories.

Open a terminal window, select the window by clicking the left mouse button in it, and type the word yppasswd. The password program prompts you once for your old password -- the one you logged in with -- and twice for your new password. Note that nothing will appear when you type your password. To ensure that no one eavesdrops on your password (or even the length of your password), the workstation leaves the cursor in place while you are typing passwords.

If you give your old password correctly and the two copies of your new password match, the program substitutes the new password for the old one in the table that the login program consults. The old password is discarded and will not be recognized in subsequent logins. (If the attempt to change the password fails for any reason, however, the old password is retained.)

A typical interaction to successfully change a password looks like this:

bourbaki% yppasswd
Changing NIS account information for user on jacobi.math.grin.edu.
Please enter old password:
Changing NIS password for user on jacobi .math.grin.edu.
Please enter new password:
Please retype new password:

The NIS password has been changed on jacobi.math.grin.edu.

bourbaki% 

After running the yppasswd program, the shell takes over again and issues another prompt. You can invoke as many programs as you like from the shell, one after another, before pressing Ctrl/D or exit to leave the shell.

Iceweasel/Firefox

Short Version

  • Start Iceweasel by clicking on the picture of the small white creature grasping a green sphere.
  • Agree to any dialog boxes that appear. They shouldn't appear again.
  • Learn how to get to the front door for this class.

Detailed Version

While some materials for this course will be available in paper, almost everything for this course (including electronic versions of paper materials) will be available on the World Wide Web. In this class, we use a version of the Firefox browser called Iceweasel. Almost all of the materials for this course will be distributed over the Web. To use Iceweasel to view materials, such as this course's syllabus and this lab, you may follow these steps:

First, prepare to use the World Wide Web by clicking on the Iceweasel icon (the picture with small white creature holding a green sphere). Iceweasel is a version of Mozilla Firefox renamed to accommodate trademark issues. More info on the relationship between Firefox and Iceweasel can be found at http://en.wikipedia.org/wiki/Naming_conflict_between_Debian_and_Mozilla. We will generally use the terms interchangeably.

The first time you run Iceweasel on our network, two message boxes might appear.

  • One box might ask you to consent to the terms of a licensing agreement.
  • One box might request permission to create some configuration files in your home directory.

You should approve of any requests by clicking on the appropriate word. The pop-up boxes then disappear; you should not see them on subsequent uses of Iceweasel.

Initially, Iceweasel displays a World Wide Web document containing some default information. You should switch to the page http://www.math.grinnell.edu/origin.xhtml, which is an entry point to the Math Department's Web site.

We expect that most of your are already familiar with a Web browser. If not, please consult with one of us or with one of your colleagues.

To find material for this course, scroll down the “origin” page for the Math Department to the list of course front doors. Now scroll down this page to find the entry for this course, Introduction to statistics, section 3, and click on it to locate the front door for this course.

You can also connect to the Web page for this class by selecting Open Web Location from the File menu and then entering http://www.math.grinnell.edu/~rebelsky/Courses/MAT115/2008S/.

Iceweasel Options

Short Version

Detailed Version

Each Linux user can configure Iceweasel to reflect her or his own preferences. Between logins, these preferences are stored in a file in the user's home directory; when Iceweasel is started during a later session, they are reinstated from that file.

Every user of Iceweasel in this class should establish a base page, a starting point for browsing. Here are the Uniform Resource Locators or URLs of some good choices:

To establish your base page, within Iceweasel, bring up the Edit menu from the menu bar and select the Preferences operation. A pop-up window appears, allowing you to configure many features of the general appearance of Icewesael. Choose the General option, if it has not been chosen already. The rectangle labeled Home Page contains the URL of some document that serves as the default. Replace the contents of this rectangle with the URL of your choice. (This does not have to be a permanent change; you can change your mind about this configuration at any time within Iceweasel.)

To erase the current contents of the Home Page Location(s) box, move the mouse pointer to the left of the first character in the box, press the left mouse button and hold it down, and drag the mouse pointer rightwards until the entire URL is displayed in reverse video, white letters on a black background. Then release the left mouse button and type the new URL; the old one will vanish as soon as you start typing. Once you have entered the new URL, move the mouse pointer onto the button marked OK at the bottom of the pop-up window and click on it with the left mouse button.

You can, of course, simply navigate to the page you want to use as your home page and then click on Use Current Pages.

You may note that the button says “Pages” (plural) rather than “Page” (singular). Since Iceweasel permits tabbed browsing (that is, you can have “tabs” within the same window that you switch between), you can have a home set of tabs. Particularly obsessive people might want to set up a sequence of tabs with say, links to outlines, labs, readings, and beyond.

Finishing Up and Logging Out

If you've successfully logged in, changed your password, started Iceweasel, selected your base page, created an icon for the Gimp, started the Gimp, created an icon for DrFu, started DrFu, and played with multiple desktops, you've completed the lab and you can finally stop.

Short Version

  • To log out, click on the menu icon near the lower left, select Log out, and confirm.
  • Do not turn off the monitor or computers.

Detailed Verison

When you are done using a workstation, you must log out in order to allow other people to use it. To log out, move the pointer onto the menu icon near the left of the front panel, click the left mouse button, and select the Log out option. A confirmation box will pop up, asking you to verify that you're ready to log out; move the pointer onto the word Yes near the bottom of this box and click the left mouse button. The Gnome windowing system vanishes, and after a few seconds the login screen reappears; this confirms that you're really logged out.

Please do not turn off the workstation when you are finished. The Linux workstations are designed to operate continuously; turning them off and on frequently actually shortens their life expectancy.

Creative Commons License

Samuel A. Rebelsky, rebelsky@grinnell.edu

Copyright (c) 2007-8 Samuel A. Rebelsky.

This work is licensed under a Creative Commons Attribution-NonCommercial 2.5 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/2.5/ or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA.