Computer Science 322
Operating Systems

We will be using several Unix-based systems within the Computer Science department. Log into and familiarize yourself with your CS Unix account in each of three environments. Later in the semester, I hope to set up a Sparc/Solaris system for our use.

• Log into a Linux system in Clapp 202. Boot into Ubuntu (the Linux distribution we use) if they're in Windows or shut down when you arrive.

  Open a terminal window and execute this command:

        uname -a > linux.txt
  

  This will execute the command uname -a, which prints a variety of information about the system you are on, and redirects the output, which would normally be printed in your terminal window, to the file linux.txt.

• Set up ssh keys to allow remote logins among departmental Unix systems without having to re-enter your password.
  1. Create a new DSA key for your CS account:

     	ssh-keygen -t dsa
     

     You may accept the default file name. You will then be prompted for a "passphrase". You could leave this blank, but I recommend using a fairly long (10 characters or longer) phrase. This will make your key much more secure.

  2. This will create two files in your .ssh subdirectory. You will next want to copy your public key (in the file ~/.ssh/id_dsa.pub) to your list of authorized login keys (in the file ~/.ssh/authorized_keys2):

     	touch ~/.ssh/authorized_keys2
     	cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys2
     

  If these commands don't make sense yet, they will soon.

• Log in remotely to the Linux server, babyred.cs.mtholyoke.edu. Use a Secure Shell (ssh) client, either from the Linux command line or from elsewhere. The system should prompt you for a passphrase (the one you just used to create your ssh key) instead of your login password. Secure shell clients are standard on most modern Unix-based systems (including Mac OS X) and are readily available for Windows systems. You may also log into babyred  from elsewhere on the Internet, in which case you will use the same password you use for the lab Linux systems. In either case, once logged into babyred, you will have access to the same files you have in your account on Clapp 202 Linux systems.

  In your terminal window that is logged into babyred, execute this command:

        uname -a >> linux.txt
  

  This is the same as what you did on your local Linux system, except that we are using >> to redirect output. The difference is that instead of creating a brand new file linux.txt (thereby overwriting the previous contents of the file), the command will append the output of uname -a to the end of the file linux.txt.

• Log into your account on the Macs in Kendade 307. The same files you saw in Clapp 202 and on babyred will be visible. Open a Terminal (go to Applications, the Utilities, and click on the Terminal icon) and execute:

        uname -a > mac.txt
  

• Log into your account on the FreeBSD system mogul.cs.mtholyoke.edu. When you are ready to do this, email me at jteresco AT mtholyoke.edu to make sure your account is ready to go.

  Once logged in, you should see your same files. On mogul, execute:

        uname -a > freebsd.txt
  

  Look at the contents of the files linux.txt, mac.txt and freebsd.txt. Which information is different? Can you guess what some of the information in these files might mean?

Identify the function of and experiment with these Unix Commands:

 
ls    cd      cp      mv     rm     mkdir   pwd
man   chmod   cat     more   grep   head    tail
ln    find    rmdir   wc     diff   tar     touch

• Give a one sentence description of each command in a file unix.txt.
• Using appropriate commands from the above list, create a directory for your work for this course called cs322, change its permissions so that only you have permission to read, write, and execute those files. Inside that directory, create a directory for your work on this lab (call it lab0), and move your .txt files from above into that directory. Show that this has worked by issuing the following command from inside of your cs322 directory:

  	ls -lad > ls.out
  

Emacs (emacs from the Unix command line) is a powerful text editor. You will want to become familiar with it if you are not already. Identify the function of and experiment with these Emacs commands:

 
C-x C-s   C-x C-c   C-x C-f   C-x C-w   C-g   C-a   C-e        
C-d       C-_       C-v       M-v       C-s   C-r   M-%

C- before a key means hold down Ctrl and hit that key. M- indicates the "Meta" key, which on most systems is Esc. To issue a Meta command, hit the Esc key, release it, then hit the key for the command you wish to issue. Use the keystrokes rather than the menus. It will save you time in the long run!

Include a brief description of each Emacs keystroke in your file unix.txt.

Learn these commands - you will use them often. Hints can be found in the Unix and Emacs web pages linked from the course website. Ask others in the lab if you're not sure how to do something in the Unix environment. Share your tips and tricks with each other.

Note: when logged into the Clapp 202 Linux systems, Emacs will open in its own window and allow you to use the mouse to move the cursor and to operate the menus. When logging in remotely, you need to forward your X11 display to your screen. To do this from the CS Linux systems, you will need to add the -Y flag to your ssh command.

Verify that you can display an Emacs window from mogul.cs.mtholyoke.edu to one of the Clapp 202 Linux systems. To get your prompt back (by running Emacs - or any command for that matter - in the background), follow your command line with an &. This will allow you to work in Emacs and your terminal window concurrently.

• Copy the C program here that computes the late penalties for this course to your account. Compile and run it, redirecting your output to a file late.txt.

  Assuming you have copied the program into a file late.c, you can do this with:

  	gcc late.c -lm
  	./a.out > late.txt
  

• Copy the file /home/jteresco/shared/cs322/make-example.tar to your account. It is a "tar file" of a small C program that demonstrates the use of multiple source files and Makefiles. Extract the files (tar xvf make-example.tar) and compile the program with make. In a plain text file called make.txt, briefly describe how make uses the rules in the Makefile to produce the executable main.

To submit this lab, place all of the files that you are to turn in (and nothing else) into a directory, change to that directory, and create a "tar file" to submit.

tar cvf intro.tar *.txt ls.out Makefile

This will create a file intro.tar in your directory. Send this tar file as an attachment to jteresco AT mtholyoke.edu by 2:40 PM, Monday, February 1, 2010.

Please include a meaningful subject line (something like "CS322 Lab 0 Submission") and use the exact filenames specified (for this lab and all semester) to make my job easier when gathering your submissions together for grading. You don't want to annoy your grader with misnamed or missing files just before he grades your assignment. Please do not include any additional files, such as emacs backup files, object files, or executable programs.