By the end of this lab, you will be able to:
There are 7 parts to this lab:
Part 1: Introduction
Part 2: Operating Systems
Part 3: File Systems
Part 4: Using Unix
Part 5: Moving Files
Part 6: Starting Your Web Page
Part 7: Submitting Your Work
| In this lab, we will highlight instructions for what you have to submit in a yellow box like this one. |
Welcome to the first lab for COS 109. In the next few hours, you'll learn how to explore and find things in the file system on your machine, how to use Unix to run programs, and how to transfer files from your machine to Unix and back. You'll also get started on your own web page. At the end, you'll be asked to submit, by email and by transferring a file, answers to some questions that will be asked along the way.
You can do this lab in a cluster in the Friend Center, where the machines run Windows Vista and/or Mac OS X and have a specific set of programs loaded. Or you can do it elsewhere, including in your room with your own computer, so long as you are running some flavor of Windows or Mac OS X. If you are not in the lab, however, you won't be able to ask questions of the lab assistants: when things don't work or when you get into trouble and can't figure out what's wrong, you're on your own.
We realize that for many of you, much of this lab will seem incredibly familiar and trivial, but for others, some or even all of it will be new. If you don't know much about computing, follow the steps in order and ask a TA for assistance at any time.
Since software and hardware change every year, often in subtle ways, inevitably something won't work exactly as described here. In particular, Vista is significantly different from XP, which was the cluster system for a few years, and it's been hard to spell out the steps as clearly as we would like. If you find something wrong with the instructions, do what you can and don't worry about it, but please let us know. Thanks.
Windows, Mac OS X, and Unix are all operating systems, which are programs that manage the resources of a computer for you. An operating system lets you run programs like browsers and word processors and iTunes; it lets you access information on disks; it lets you use attached devices like printers and MP3 players; and it lets you communicate with other machines via a network.
"Windows" is a family of operating systems from Microsoft. Microsoft cranks out a new version every few years: Windows XP has been around since 2001, Vista arrived in 2006, and Windows 7 is only a month away. Mac OS X is the family on Mac's; Snow Leopard, the latest, arrived a month ago. Unix and Linux are also operating systems, not from Microsoft or Apple, that run on a wide variety of hardware. All operating systems perform the same basic functions, though with myriad differences in style, philosophy, and details. Most consumer devices like MP3 players and cell phones also run some operating system, though simpler and better hidden from you.
One of the main functions of an operating system is to provide an environment in which you can run programs. Operating systems allow you to run several programs at once, switching your attention from one to another at will. Some, like Unix, are mostly controlled by typing on the keyboard. Others are graphical and are mostly controlled with a mouse. Mac OS X has a glossy mouse interface but there's a Unix implementation in the background.
Word processing is one of the most frequent computer tasks, and most people have used Microsoft Word to process documents. But there are plenty of times when you don't want a formatted document nor the proprietary Word format. Every system has a variety of editors that let you create plain ASCII text with no additional formatting or other goo.
On Windows, you can use Notepad or Textpad, or you can use Word or Wordpad if you save your files as ".txt" format. You can find these programs from the Start menu in places like Programs | Accessories. We advise against using Word for text files.
On a Mac, you can use TextEdit (in Applications). Use Preferences / New Document to set "Plain Text". Do not use "rich text format" (.rtf). Unfortunately TextEdit is sometimes too smart for its own good. The safest way to use it is to open a blank TextEdit window, set the mode to plain text, then use File / Open to load a file.
For the rest of this lab, you will record your work in a plain ASCII text file as you go along, and then copy it into an email at the end.
Do this to begin collecting data for submission:
If you are using a cluster machine, you should save the file on your Desktop, which is really stored on a machine at OIT. If you're on your own machine, save it anywhere convenient.
Leave your editor running. You will be adding content to this file for the rest of the lab. Each time you add something, save the file; this (usually) protects you in case something goes awry, and is always a good idea.
A file system is a part of the operating system that manages all the data stored on the computer, in a form that is convenient for users to save information, organize it, and retrieve it as needed. The same organizing structures that are useful for the information on a hard disk are also useful for removable media like USB drives, CD-ROMs and MP3 players, and even for information physically stored on other computers and accessed through a network, so these are packaged as file systems as well. Although the physical structures vary greatly, the operating system makes them all look the same to users, an example of implementing the same logical organization with different physical mechanisms.
Information in a file system is organized hierarchically: at the top level is a set of folders (often equivalently called directories) and files. A folder contains the names of files and folders that are grouped together for some purpose. A file holds specific information, such as a Word document, a spreadsheet, a mail message, a picture, a song, or a program like Word or TextEdit.
On Windows, the usual organization creates a file system on the computer's hard drive, in a folder called (for ancient historical reasons) "C:". For even more ancient reasons, the now extinct floppy drive is called "A:". If there is a CD-ROM or DVD, it takes the next letter, and is thus often "D:". Other plug-in devices take up the next free letters, so if you plug in a USB drive, it will probably be called "E:".
Other "drives", like network connections, have even more arbitrary letter names; at Princeton, student files can be stored in a big file system on a central OIT computer and your part of that file system is accessible from a PC or Mac as your "H:" (for "home") drive. This may already be set up for you; for instance on Vista the Personal Files icon accesses your H: drive, and on Mac OS X, there's a folder called Mac_Cluster that leads to your H: drive.
This OIT page explains how to make your part of the OIT Unix file system visible on a Windows PC, and this OIT page explains how to make your part of the OIT Unix file system visible on a Mac.
There are a variety of way to explore the contents of these file systems. The simplest, though not the most flexible, is to double-click on something and see what happens. If you double-click on a folder, it will list whatever is contained therein: each double-click on a folder expands its contents.
A double-click on a file, however, typically executes a program that is associated with the presumed type of information that the file contains, as indicated by the suffix of the name. For instance, filenames ending in .doc are assumed to be Word files, and clicking on such a file will cause Word to be started up to process that file. Filenames ending in .txt are usually associated with Notepad or TextEdit, so another way to start an editor is to click on a file like lab1.txt. You should be cautious about this mechanism if you don't know what you're doing, however. Files of type .exe on Windows are "executable" files -- programs that do something -- and you don't want to run them unless you know exactly what will happen.
Although a Mac .app is actually a folder, double-clicking on it runs the executable program hidden within, so the same cautions apply.
Now do one of the two sections below according to the operating system you're using.
Both the My Computer or Personal Files icons, and the Save (and Save As... or Open) dialog box allow you to look through folders and find files. If you want to move files around, however, or find a program and start it, then Windows Explorer (not to be confused with the Internet Explorer browser) is convenient.
Use the Start Menu to find and start Windows Explorer; it will usually be under Programs or Accessories. (You can also type "explorer" in the Run dialog box, which is on the Start Menu or under All Programs | Accessories.)
Explorer gives a split-screen view of the file system. To the left is a folder hierarchy. When you click on a folder, its contents will be displayed on the right. Notice that some folders have +'s or -'s (XP) or little triangles (Vista) next to them. This means that the folder has subfolders. By clicking on the + or - or triangles, you can flip between the condensed view and the expanded view.
Find the file lab1.txt by clicking "Desktop".
You should see all of the Desktop contents displayed at the right, including your file if you saved it there. (The names will roughly correspond to what you actually see on the Windows Desktop.) Now look through the menus at the top and try left-clicking and right-clicking on various things to see what options are available. Don't choose any of these options yet! To move a file, click on it once, then drag it to its new location on the left. You can also right-click on it and select "Cut" to remove it completely, or "Copy" to make a copy of it. Then you can click on a different folder and select "Paste" to put the copy there. These menu options are also available in XP's "Edit" menu but only visible in Vista if you push Alt.
The various programs for displaying directories normally give an almost worthless visual display of icons. You can see much more useful information by selecting View from the menu, then Details. You can also sort the items in order by date or size or type, either by selecting View, then Arrange Icons, or by clicking on the corresponding column heading. Experiment with them to see what happens.
In spite of its name, Explorer is most useful when you already know approximately where you're going in the file system. If you know even part of the name of a folder or file, however, you can often find it most easily with a different program. Select Start, then Search, then "For Files or Folders...". For Vista, use Start | Search | Advanced Search, check the "include non-indexed...files" option, then set Name to .exe and Location to Cluster_HD (C:). Or you can just type name:.exe in the search box on the Start menu, then click "Search Everywhere" to bring up a search window; then select Advanced.
You are now going to try to find some interesting files (and some boring ones too, but that's life). Do the following operations.
Save each time, so in case something bad happens, you still have the information.
If you click on the icon for your hard drive, you will be running Finder, the all-purpose program for exploring the Mac file system.
Finder gives a multi-screen view of the file system that can be formatted as large useless icons (the default), or a list with details, or multiple columns. To the left is a folder hierarchy. When you click on a folder, its contents will be displayed either below or to the right. Notice that some folders have right-pointing or down-pointing triangles next to them. This means that the folder has sub-folders, and you can expand or contract the view by clicking on the triangle.
Find the file lab1.txt by clicking "Desktop".
You should see all of the Desktop contents displayed at the right, including your file. (These should correspond to what you actually see on the Desktop.) Now look through the menus at the top and try clicking on various things to see what options are available. Don't choose any of these options yet! To move a file, click on it and drag it to its new location on the left. You can also click on it and select File / Move to Trash to remove it completely, or Edit / Copy to make a copy of it. Then you can click on a different folder and select Paste to put the copy there. All of these options are also available in the Edit menu.
As mentioned above, a Mac .app is really a folder, with an executable file several levels down. As an experiment, use Cntl-click (that is, clicking while pressing the Control key) on the name, then Show Package Contents to expand the folder; look in Contents and then in MacOS.
If you type the prefix of a filename into the search box at the top right corner of a Finder window, you'll get a list of files and folders with that name. (You can't search for a part of a name, however.) You are now going to use this to find some interesting files (and some boring ones too, but that's life). Do the following operations.
Save each time, so in case something bad happens, you still have the information.
At the end of this part you should have 5 lines in lab1.txt.
Unix is an operating system; like Windows and Mac OS X, it controls the resources of a computer on your behalf. Unix has been around a lot longer than other systems, and runs on many more different kinds of computers. Many of the Internet and Web services that you use run on Unix machines, and most of the central computing services at Princeton are based on Unix. The web pages that you will create in the next few labs are also stored in files on Unix systems, so it will help you to understand at least the rudiments of how to access and use the campus Unix systems. The Linux operating system is a variant of Unix, so anything you learn about Unix will apply to Linux as well; indeed, you will use OIT's Linux systems for this lab.
Mac OS X is also a Unix variant. Although the Mac has an even glitzier graphical interface than Windows, underneath is the full power of Unix, a nice combination. If you're using a Mac, start Terminal (in Applications / Utilities) and all of the Unix commands described here will run the same.
Other Unix variants include FreeBSD, AIX, HP-UX and Solaris. We will lump Linux and all of these under the generic term "Unix", since for our purposes they are all the same.
Unix systems are more reliable and secure than Windows (or so it is believed by Unix aficionados) and present programmers with more convenient access to the internals of the machine. As a result, although Windows is dominant in offices and homes, Unix is often used to support infrastructure functions (the back office); familiar sites like Google, Amazon and Yahoo all use Unix or Linux.
| Using the Webserver Search at
netcraft.com, find
another major web site that uses Unix or Linux.
Add a line to lab1.txt with the site name
and the name of the specific Unix variant.
Find a major web site (other than microsoft.com or msnbc.com) that doesn't use Unix. Add a line to lab1.txt with the site name and the operating system name. |
In this part of the lab, you will see how to connect to a Unix computer provided by OIT. You will also see how Unix provides for the permanent storage of your files, since the cluster systems only provide transient storage.
If you are using a public cluster machine, you can't save files on it, since they likely won't be there if you return even a day later. You have to store them in some central location. That central location is a Unix system run by OIT. Files are stored there, and backed up onto other systems as well so you can recover them in case of a disaster. Similarly, your Princeton email inbox is located on an OIT Unix system, so it can be centrally administered and accessed from any machine on (or off) campus.
Most of the time you can save and retrieve files from the central system without using Unix directly; the Windows or Mac H: folder that you saw earlier gives you most of the access you would ever need. And you can read mail just fine from a mailer or a browser on your own PC or Mac.
But sometimes you simply have to get to the place where the information really is. For this, you have to use a program that lets a user on one computer use another computer over a network connection. There are a variety of options. One common choice is a program called SSH, which stands for "Secure Shell". The important word here is "secure" -- information that travels between your machine and the other system is encrypted, so it can't be eavesdropped on by anyone along the way. This is nice if you're exchanging intimate messages with a significant other, and it's even nicer if you're sending your password to the other machine.
Another choice, which is encouraged by OIT on Windows cluster machines, is a program called PuTTY, which does much the same thing. The cluster machines have PuTTY, and you can download for your own machine from here. If you got the standard software distribution, it's already installed. (In spite of its name, PuTTY has nothing to do with Princeton University; it's an open-source program from England.)
On a Mac, you can also use the Terminal application to run SSH and access your OIT account.
Follow these instructions to connect to Arizona, which is a group of OIT computers running Linux. We'll just say "Unix" from now on, since things are mostly exactly the same.
Start by opening SSH or PuTTY. This process will be different depending on which program you use and what operating system you have. Instructions for Mac OS X and Windows are provided below. In either case, if you get a message that says something like
answer yes. You may also be asked whether you want to save the host key to the local database; "no" is fine in all cases, but you can also say "yes" if you're on your own machine.The authenticity of host 'arizona.princeton.edu (128.112.128.42)' can't be established. RSA key fingerprint is ab:62:85:30:20:81:68:a2:7b:df:a2:72:6e:8f:92:a0. Are you sure you want to continue connecting (yes/no)?
Run PuTTY by selecting it from the Start menu. It will likely be listed under "(All) Programs | ..." If that fails, consult a TA.
If there were no problems you will be asked for your password. Enter it at the appropriate time, then push Enter. You can ignore (No or Cancel) anything else that happens first.
Note: Your password may not be echoed with asterisks as is common on PCs and Macs; there may be no response at all. Just type and push Enter when you're done.
If you are running Mac OS X launch SSH through a program called Terminal. This program is located in your Utilities folder, which itself is in the Applications folder.
Once you have Terminal running, type the following line:
ssh your_netid@arizona.princeton.edu
Replace your_netid with your own netid. For example, if your netid is joesmith, you should type ssh joesmith@arizona.princeton.edu. After you have typed this line, press Enter or Return.
You should see a flood of text lines that finally ends with a "prompt" that looks like this:
flagstaff.Princeton.EDU%The prompt says that you are now connected to one of the computers in the Arizona cluster (flagstaff, phoenix, tucson or yuma) and it's ready to do your bidding.
As seen here, Unix has a very different flavor from Windows. Rather than running a program by clicking on an icon or selecting a menu item, you type the name of the program in a window where a prompt is displayed. Keyboard commands with cryptic names like "ls" and "cd" run programs to help you navigate Unix and can be typed in whenever you see a command prompt like
yuma.Princeton.EDU%
Behind the scenes, Unix, like Windows and Mac OS X, maintains a file system with files and folders (though it calls folders "directories"). When you first log in, you should be in a directory called your "home" directory. This is loosely like C: on Windows or Home on a Mac; it holds all of your files, most of which cannot be read or even seen by other users. And it's the same directory that is set up as the H: drive from a PC or a Mac.
Before you start typing Unix commands, familiarize yourself with the way the commands will be written in these lab instructions. Whenever you are told to type something, what you should type will be in this computer-like font. Similarly you will sometimes have to substitute information of your own; we will use this italic computer-like font, as in your_netid. In all of these, pay attention to case -- Unix distinguishes between lower and upper case letters -- and to spacing.
Try the following commands. For each, type the command name, then push Enter or Return.
mkdir cos109
and then push Enter. If you now run the ls command again, your new directory should be there. This is rather like File | New Folder in Explorer. If you already have a cos109 directory, you will get a warning message, which you can ignore.
cd cos109
This will move you to the directory
you just created. To get back to your home directory, type
cd by itself. You can also type cd ..
to move up one level in the file system, and you can type
pwd ("print working directory") to print the name of the
directory you are currently working in.
who
Can you find your own netid among the others? Typing who | more will let you see the names one screen at a time.
Why use Unix? It largely depends on what task you are trying to accomplish. For example, Windows has an enormous collection of useful programs, many of which have no Unix equivalent, and Windows comes installed on most PC's. Unix is a good environment for writing programs, however, especially programs that are meant to work on more than one kind of computer, so it is often preferred by programmers. It supports a bunch of users on one machine, which Windows does not. Meanwhile, don't worry if Unix seems strange at first. You won't need to use it very often, but it is helpful to know how to move around in it. And if you own a Mac, knowing Unix will give you a new way to use your computer.
Note: When logged into UNIX, you may have to use the "DEL" or "Delete" key instead of "Backspace" to delete a character.
At this point, you should have 11 lines in lab1.txt.
There are a variety of ways to copy files from one place in a file system to another, or from one file system to another. In Windows, the clearest and most uniform way is to select the file of interest by a single mouse click in a program like Explorer (so it is highlighted), select Copy from the Edit menu or by right-clicking on the filename, then select the folder where you want the copy to appear (so the folder name is highlighted), then select Paste from the Edit menu or by right-clicking.
There are shortcut mouse actions for Copy (Ctrl-C or, on a Mac, Option-C) and for Paste (Ctrl-V or Option-V), and those are well worth learning. In some situations you can "drag and drop" the file to make a copy, which is very graphical and intuitive. But be cautious with drag and drop, since in some contexts, it means "copy" and in others it means "move", and these are not the same operation: "move" means to remove the file from the place it was and put it into a new place, leaving you with a single instance, while "copy" leaves you with two instances.
Copy the file lab1.txt that you are building up on the Desktop to your Unix cos109 directory as seen through the H: drive, Personal Files, or the Mac equivalent.
After the file is copied (it should take no time at all) verify that it seems to be correct: the file exists in both places, and it has the same size and sensible modification times.
Somewhat irritatingly, Windows Explorer does not always update the display of a folder when a change is made, or it may put the entry at the end instead of in order. To be sure you have a consistent and up to date display you may need to use View / Refresh. Finder does this better, though it can be slow to notice a change.
Here is a chance for you to use your newfound Unix skill to see if the file was copied correctly.
Connect to Arizona again if you closed the PuTTY/SSH window already. As always when you first log in you will be in your home directory. This is the same directory as your H: drive. In your PuTTY/SSH window type
cd cos109to verify that the file you just transferred is there and about the right size. It should be about the same size as in Desktop. The file size in bytes is the number just before the date.
ls -l
|
Add a line to lab1.txt with the size reported by Unix and the size reported by Explorer or Finder (e.g., Unix 395, Windows 1KB). |
The last two things that you did, changing to a directory with cd, and listing the contents of the directory with ls, are much the same as double-clicking on a folder. When you double-click you're telling the operating system "I want to move to this directory, and I want to be shown what's in it."
When you're done this part, you can quit PuTTY/SSH if you like; type the command exit or kill the window.
A web page is a text document similar to the one you've been creating for this lab, but there are two important differences between lab1.txt and a web page. First, a web page is stored in a particular folder so it is visible on the web. Second, whereas lab1.txt is written so that it's easy for a person to read, a web page is written so that a browser can format it the way you want. With the second condition in mind, let's start making a web page.
Open a new document in your editor and save it as lab1.html. If you're using TextEdit on a Mac, be careful: as noted above, open a blank TextEdit window, set the mode to plain text, then use File / Open to load a file. This should avoid the unwanted conversion to rtf format.
Web pages are written using a special language called HTML, which stands for HyperText Markup Language. Mostly HTML is ordinary text, but it includes formatting information that describes the layout. This extra information is contained in a set of tags, which are ordinary text surrounded by < and > signs. They give the browser information about how to display the text.
The skeleton of any web page looks like this:
<html>
<head>
<title> Title of the Web Page Goes Here </title>
</head>
<body>
Content of the web page goes here
</body>
</html>
In Lab 2 we will go into detail about what exactly this means, but for the time being it's safe to simply copy this text and paste it into your new document. Remember to save the document every time you make a change.
Once the document is saved as lab1.html, start your web browser of choice. You can preview your page by opening the document which you just saved in the browser, using File | Open. When the Open dialog comes up, navigate to where the file was saved and open it. (You could also double-click on lab1.html in Explorer or Finder.) This will show you exactly how the document will look to other people who visit your page. Right now it isn't very interesting, since it just says "Content of the web page goes here", so next you're going to fix that, by adding content and a title.
| Replace
"Title of the Web Page Goes Here" by a brief title.
Replace "Content of the web page goes here" by your name. |
Test these modifications by loading the page in your browser as described above. You will have to save the file in your editor and then Reload in the browser before you will see the change; don't forget this!
Unlike the Title tags, we put the Body tags on their own lines rather than sharing a line with the content. This illustrates an important point of HTML syntax. The browser doesn't care where you break lines of text while you're writing your page -- it just ignores line breaks. Thus web page designers have to use a special tag to designate where to break lines when the page is displayed. This tag is the <br> tag.
| Add a <br> tag after your name, then
add four more lines with the following information:
|
Test this modification by saving and loading the page in your browser.
Each piece of information should appear on its own line, so be
careful where you put your <br> tags.
Now that you've created your web page, you have to make it available
to others. Log in to Arizona if necessary. Copy your newly created
lab1.html file into your public_html directory (which
should already exist).
Once these steps are completed you can test the results by going to
http://www.princeton.edu/~your_netid/lab1.html
You may have to change the permissions on your file to let people
see it. If your browser tells you that you don't have permission to
access the file, then log in to Arizona again and type the command
If you can't access your page or if it doesn't display correctly,
ask the TAs for help. This
OIT page
may also help.
At the end of most labs, you will be asked to mail your results to
cos109@princeton.edu. Be sure to include everything we asked
for. If you have comments or suggestions, we'd be happy to get those as
well.
Make sure you've done all the steps.
Make sure your web page is accessible at
http://www.princeton.edu/~your_netid/lab1.html.
Ask a friend to look at it from his or her browser. If they can see
it, so can we; if they can't, we can't.
Mail us the text of the file lab1.txt that you have been
laboriously creating, which should now contain 12 lines. Just copy and
paste it. Do not make it an attachment! Use the subject line "Lab 1 --
Your Name and netid".
Make any additional comments or observations at the end of the
message and add your name.
Send the mail to cos109@princeton.edu. Please send the
mail from your Princeton account, not Gmail or the like; otherwise we may have
trouble identifying you.
Send a copy of the mail to yourself as well. This is a good check on
whether you really sent the right stuff. Paranoids will make sure that
this mail arrives and looks right before they leave the lab or turn off
their computer.
Files on a public computer are routinely erased, so they won't be
there for long after you stop using it. This won't matter if you're
using your H: drive, as you would normally do. If you're working on
your own machine, it's wise to back up your work on your H: drive
or a flash drive as well. Putting things on a flash drive routinely is
a good habit to get into.
If you've completed the lab, sent your email to
cos109@princeton.edu, and made a backup copy of your work,
you're all done.
Sharing Your Page With the World
Copying a file from a Mac to your OIT public_html folder
is trickier than it ought to be.
This OIT
page describes several options. It is also possible, and probably
easier, to use Unix commands. In a terminal window on your Mac, change
to the directory that contains your lab1.html (e.g.,
cd Desktop) and
use the scp (secure copy) command:
scp lab1.html your_netid@arizona.princeton.edu:public_html/lab1.html
chmod 755 public_html/lab1.html
Part 7: Submitting your work
Check your work
Mail us a copy of your work
Be sure to save your work