• Which machines can I use?
• How do I set up my Windows NT/2000/XP machine to be able to access AFS files?
• How do I set recursive permissions on AFS?
• How do I send pdf files to the printers?
• How do I read news?
• What CS newsgroups are available to students?
• What other local newsgroups are there?
• How can I get information about the video conferencing room in Sennott Square?
• How can I access the wireless network in Sennott Square?
• How can I look and edit MS Office (Word, Excel, etc) files in the UNIX machines?
• How can I install programs (for everyone to use and not using my own disk quota) in the UNIX machines?
• How do I unspam/de-spam a message that has been labeled as SPAM by SpamAssassin?
• About your Windows profile space

1. Which machines can I use?
2. How do I connect to the UNIX servers?
3. Which printers can I use?
4. What is appropriate use of the printers?
5. How do I send files to the printers?
6. How do I send pdf files to the printers?
7. What are the policies regarding departmental photocopiers?
8. How can I access the wireless network in Sennott Square?
9. How can I get information about the video conferencing room in Sennott Square?

1. Why can't my directory under public/html be seen anymore (it used to work)?
2. How do I change my password?
3. How do I check my e-mail?
4. What is my e-mail return address?
5. How do I read my e-mail from home?
6. What is the URL for my World Wide Web (WWW) home page?
7. How do I read news?
8. What CS newsgroups are available to students?
9. What other local newsgroups are there?
10. What kinds of programs are there on the CS machines?
11. How do I set up a plan file to help others locate me?
12. How do I set my project file for use with the finger utility?
13. How do I change my name and office as displayed by the finger utility?
14. What information is available online?
15. How do I logout?
16. What do I do if I suspect I am having a hardware or software problem?
17. How do I use the Vacation program?
18. How do I set up my UNIX account to use LaTeX?
19. How do I set up my UNIX account to run other software in the Department?
20. How do I set up my Windows NT/2000/XP machine to be able to access AFS files?
21. How do I verify if the message I got about a virus is true or not?
22. Why do I sometimes get 2 requests for passwords when logging into Linux?
23. How can I look and edit MS Office (Word, Excel, etc) files in the UNIX machines?
24. How can I add to my $PATH variable?
25. How can I install programs (for everyone to use and not using my own disk quota) in the UNIX machines?
26. How do I create a symbolic link in UNIX?
27. How to have email forwarded to another address?
28. How to look up email aliases?
29. How can I filter spam?
30. As an Instructor, I want to limit the network access during the classes I teach. What can I do?

1. What do I do if I need more disk space?
2. How are my files set up?
3. How do I control access to my AFS files?
4. How do I set recursive permissions on AFS?
5. How often are my files backed up?
6. I can't rlogin from a system listed in my '.rhosts' file. Why not?
7. When I do an "ls -l" on the '/afs' directory my terminal hangs. Why?
8. How do I access other AFS cells?
9. I frequently have problems accessing files after I have been logged in for a long time. Why?
10. How do I clean up my account to get more space (core files specifically)?
11. About your Windows profile space...

Other Important Topics

1. What do I do if the pipes are leaking, the elevator doesn't work, my room is too hot or too cold?
2. My Pitt ID will not open the doors!
3. I need a projector, a laptop or cards for the copy machine!

HARDWARE & PROCEDURES

Which machines can I use?
Several UNIX machines are available as the department's general use compute servers.  For those in need of Solaris 9, please connect to blitz.cs.pitt.edu.  For Red Hat Enterprise Linux, please connect to elements.cs.pitt.edu (or) linux.cs.pitt.edu.  This will connect you to to one of  the dual dual-core processor PCs ( Dell PowerEdge 1950s) in the elements cluster.

There are also 2 computing labs available for your use.  The Link-to-Learn lab in room 5712 and the Moye Lab in room 5806 have PCs running Windows and can, in addition, be used to connect to the UNIX compute servers mentioned above.

How do I connect to the UNIX servers?
You can connect to the servers using the F-Secure SSH Client program that has been installed on the departmental Windows machines or by using ssh from another UNIX machine.  For security reasons, the department does not accept telnet connections to our servers.  Also, if you have X-Windows client software, you can connect to our servers using it.  Often listed on the chooser menu of X-terminal programs are workstations in offices and common areas that are not department compute servers. These machines may be used, but please be courteous to users logged on at the console of these machines as these machines are generally for their use and you are the guest.

• If you are trying to log into the console of a UNIX workstation, press return once or twice to clear the screensaver. Enter your username and password at the prompts; most workstations in the department are running the X Display Manager interface (XDM).
• If you are dialing in on a modem, you will need to have a computer account with the University's CSSD department. As a registered student you should already have this account. You will need to dial the University's modem line and connect to their terminal servers at 412-297-PITT (412-297-7488).

The printers ps, ps2, ps6w and ps6n are available to be used appropriately (see next question) by all faculty, staff, and graduate students in the department. The printers and their locations are:
 

ps
    5414, 5th floor Mail Room

ps2
    6146, 6th floor Mail Room

ps6w
    across from room 6415

ps6n
    across from room 6103

link
    5712, Link to Learn Lab

moyepr and color-moye
    5806, Moye Lab

Some faculty also provide printers for their students to use.  The use of these printers is restricted.

What is appropriate use of the printers?
The printers should be used only for class work, departmental business, and supervised research. The printers are not for personal business! There should be no printing of newsgroup postings, web pages, mailboxes, or pretty pictures. Only one copy of each file should be sent to a printer. If multiple copies are needed, please use the photocopier!

How do I send files to the printers?
For general printing of text and PostScript files there is the standard UNIX lpr command and there is the Adobe enscript command.

The lpr command will print both text and PostScript files with limited formatting and control options. You must specify which printer to send your output to. The syntax is:

The enscript command, on the other hand, converts text files to POSTSCRIPT language format for printing. It will perform the conversion according to the command line options specified (see the man page) and spool the file for printing in one operation. Here again, you must use the -P option to specify the printer you want to use. Enscript has many options including page numbers, page headings, two column output, landscape mode printing, and more. See the man page for more information.

If the -P option is not specified, both commands will look to the PRINTER environment variable set for your shell and try to send the output to this printer. The command 'printenv PRINTER' will display the value for this variable. The command 'setenv PRINTER mib' will set the value of this variable to "mib". The setenv command is typically set in the .cshrc file located in each user's home directory.

Note that compressed files must be uncompressed before they can be printed. Printing a compressed file will jam the print spooler and hold up subsequent processing. If you suspect this has happened, send e-mail to the tech staff. Compressed files can usually be recognized by a .z, .Z, or .gz suffix. For more information on file compression, see the man pages for compress or gzip.

PostScript files that are received via e-mail must be edited before printing so that the line beginning with "%!PS" is the very first line of the file. Remove all unrelated mail file headers and text that may appear before this line.

To use the printers under Windows you must have the printers installed on your workstation.  Send an e-mail to tech@cs.pitt.edu to request that a printer be installed on your workstation.

How do I send pdf files to the printers?

pdf files cannot be sent directly to the printer. The correct way to do this is to open the file using Adobe Acrobat Reader and print the file from within that. In UNIX, the command for this is: acroread <filename.pdf>.

What are the policies regarding departmental photocopiers ?
Photocopy machines are available in the Mail Rooms (5414 and 6146).

Copy cards can be obtained by students for a one time cost of $1.00 per card plus 5 cents per copy. Please see Kathleen in room 6135 regarding new cards and increases in copy units.

Transparencies are available at cost to students (30 cents) preparing for presentations related to their dissertation.

Photocopies and transparencies are provided by the department to TAs for class-related presentations and handouts.

How can I access the wireless network in Sennott Square?
Access to our wireless network is limited to CS faculty, staff, graduate students, and others that have the sponsorship of a full time CS faculty member.

Set the wireless-network name (SSID) on your laptop to:

Pitt CS Wireless

Make sure that any encryption (WEP) is turned off. You also need to send an email to tech@cs.pitt.edu containing the MAC address on the back of your wireless card in order to be added to the access control list.

How can I get information about the video conferencing room in Sennott Square?
The users manual for the Eli Lilly Conference Room in 6106 Sennott Square can be downloaded from here.

SOFTWARE & PROCEDURES

Why can't my directory under public/html be seen anymore (it used to work)?
The new server will not default to a directory listing if there's no index.html file. There are two solutions: (a) generate a quick index.html file, or (b) you can disable this feature on a per-directory basis by creating a file called .htaccess in the directory in which you wish to enable browsing. In this file, put a single line that says

Under AFS, this command replaces the UNIX "passwd" and "yppasswd" commands since user passwords are controlled and verified by the AFS Authentication Server, Kerberos.

The second password is for the Microsoft Windows environment.  You can change this password press CONTROL-ALT-DELETE while logged into your workstation and select the "Change Password" button.

While many people use the same password for both environments, it is important to remember that they are seperate, independent systems.  Changing the password in one environment has no effect upon the other.

How do I check my e-mail?
To read or send e-mail, one of several mail readers that are installed on the department systems can be used.  These include: pine, mutt, Netscape, Mozilla, Outlook and Outlook Express.  You may also use any modern web browser and connect to https://webmail.cs.pitt.edu.  You can login to WebMail using your UNIX account username and password.  This website may be accessed from anywhere on the Internet and no setup is required on your part.

What is my e-mail return address?
Your e-mail address is your username (i.e. your login name) followed by "@cs.pitt.edu".  For example, if you login with the username of "john", your address for this login account would be "john@cs.pitt.edu".

How do I read my e-mail from home?
The Department has machines setup as IMAP, POP, and SMTP servers. You will need to configure your mail reader on your home PC to make use of one of these servers:

IMAP: imap.cs.pitt.edu
POP:  pop.cs.pitt.edu
SMTP: smtp.cs.pitt.edu

What is the URL for my World Wide Web (WWW) home page?
Setting your web browser to the URL: 'http://www.cs.pitt.edu/~username'; will display the file ${HOME}/public/html/index.html, if it exists.

How do I read news?
News can be read via your favorite news reader program, such as Netscape, by setting the news server to the appropriate entry. To set the news server (newsgroup server) to the appropriate name for the correct set of newsgroups, read the next two FAQs about the CS newsgroups and local newsgroups.

• Using Netscape to read news: Link to tutorial.
  
  
• Using Mozilla to read news: Link to tutorial.
  
  
• Using Pine to read news: Link to tutorial.
  
  
• Using Outlook Express to read news: Link to tutorial.
  
  
• Using Mozilla Thunderbird to read news: Link to tutorial.

What CS newsgroups are available to students?
The following news groups are available to students through the usenet server operated by the department.

cs.info 		Get help from Student/Faculty
cs.grads                Anything of interest to graduate students.              
cs.ugrads               Anything of interest to undergraduate students.         
cs.talks                For talks inside and outside the department.            
cs.announce             For "official" departmental announcements.              
cs.technews             For tech news.                                          
cs.general              For everything else.                                    
cs.users.mac            Anything related to MAC.                                
cs.users.linux          Anything related to Linux.                              
cs.users.windows        Anything related to Windows.                            
cs.users.sun            Anything related to Sun OS.                             
cs.test                 For "test please ignore postings".                      

What other local newsgroups are there?
An example of some local newsgroups of interest to CS students might be:

pitt.general  - University of Pittsburgh
pgh.general - Pittsburgh area news

What kinds of programs are there on the CS machines?
All the typical UNIX utilities for job control, file manipulation, networking (ssh, sftp, etc) and C compilation and debugging can be found on each of the department systems, as well as a lot of public domain software.

Some directories worth mentioning are:

/usr/local/bin          - contains host dependant software not part of
                          stanard UNIX and may vary from machine to machine
/usr/local/X11/bin      - contains host dependant X11 software
/usr/local/contrib      - contains user contributed & maintained software

How do I set up a plan file to help others locate me?
Your .plan file is displayed when other people use the finger command with your username, as in "finger jdoe", or "finger jdoe@oxygen", or "finger jdoe@pitt.edu".

This file is a good way of letting other users optionally know a little about you or what your current office/teaching hours are.

Simply create a file by the name ".plan" in your home directory. All text in this file will be displayed when the command 'finger myusername' is executed. By default, all files created in your home directory are world readable under AFS; this will allow others to see your .plan file when they use the finger utility with either your username or some portion of your proper name that also appears in the system password file.

How do I set my project file for use with the finger utility?
The .project file in your home directory is also a simple text file. This file differs from the .plan file in that only the first line in this file will be displayed by the finger command and is generally used for job titles or project associations of the user.

The same requirements for AFS read access apply to this file as mentioned for the .plan file in the previous question.

How do I change my name and office as displayed by the finger utility?
Some user information displayed by the finger command comes from the system password file and can not be changed by the user. Send a request to tech@cs.pitt.edu.

What information is available online?
General information about both the University and the Computer Science Department can be found in their respective World Wide Web home-pages (http://www.pitt.edu and http://www.cs.pitt.edu).

More specific information regarding the University's computing facilities can be found in the directory /afs/pitt.edu/public/info/pittdoc. This directory contains documents in both text (.doc extension) and PostScript (.ps extension) formats. You can find many "help sheets" here on topics related to specific tasks and software packages as well as back issues of CIS's newsletter Connections and the ethical use of University computing facilities.

For Graduate Students, there is the Graduate Student Organization user account. Change directory to ~gso and see the README file. The CS/GSO Bulletin and other graduate student related information resides here.

How do I logout?
Logging out depends on the UNIX shell (command line parser) and/or the windowing system (if logged in at a UNIX workstation) you are using.

By default, typing Control-D will exit any of the UNIX shells. In this case, Control-D indicates the end of file; here the end of the standard input (stdin) stream. Be careful when using programs that use Control-D to terminate; typing one too many Control-Ds may actually log you out of the system prematurely. Most UNIX shells allow this feature to be disabled by setting a shell variable called "ignoreeof". When set, the user must type exit or logout, depending on the shell, to either leave the current shell or logout of the machine completely.

The following table summarizes the different shells and their various means of termination: 

What do I do if I suspect I am having a hardware or software problem?
If applicable, consult the man page to be sure you are using the command correctly. In many cases, other students may be of help. If the problem persists, you suspect a machine is down, or can not access files you previously had access to, send e-mail to tech@cs.pitt.edu. Describe the problem as thoroughly and succinctly as possible, including as necessary, the name of the command, the path of the command, the machine in question, and other pertinent symptoms/conditions. In some cases it may be necessary to include the conditions required to duplicate the problem.

Mail sent to tech is regularly read by the CS Department's technical support staff.  In most cases, we can respond to your request rather quickly, however some requests will take longer.  Please be patient.

IMPORTANT NOTE:  Now, every email sent to tech@cs.pitt.edu is entered into our ticket system.  You can view the progress of your request by visiting the ticket system and entering your ticket number.

How do I use the Vacation program?
To configure vacation so that it will automatically return a message to each person who sends you mail, you will need to perform the following steps one time only:

1. Create/edit a ".vacation.msg" file. Create a .vacation.msg file in your home directory containing the message that you want vacation to return to each sender. It should be a complete message including headers. If your name was "John Brown", your username was "john", and your domain name was "cs.pitt.edu", you might create a .vacation.msg file containing:

From: john@cs.pitt.edu (John Brown)
Subject: I am on vacation
Precedence: bulk

I am on vacation until Aug. 1st.  In my absence, please refer
all urgent business to Jane Smith.  Her e-mail address is
jane@hermachine.company.com.

-- John Brown

% mkdir .vacation
% /usr/afsws/bin/fs sa .vacation mailserver rlwk
% ln -s .vacation/.vacation.db .vacation.db

3. Initialize the vacation database in your .vacation directory by invoking vacation with the -i flag.

% /usr/local/bin/vacation -i

\myusername, "| /usr/local/bin/vacation myusername"

5. Make sure that the permissions on your home directory and your ".forward" file are correct (ignore the chmod for ".procmailrc" is you dont have one).

% chmod 755 ~/
% chmod 644 ~/.vacation
% chmod 644 ~/.procmailrc

How do I set up my UNIX account to use LaTeX?
Edit your .cshrc file or equivalent and add the following statement at some point after the code used to set your shell "PATH" variable:

source /usr/local/etc/latex.env

Users can make additional modifications to the variables set in this file if necessary.

NOTES:
LaTeX v0.4 is currently installed on all department systems. Please see the LaTeX announcement under News & Announcements for additional information.

Note that if you are using the department standard cshrc script you need not do anything. This shell script executes latex.env for you. Customizations to your latex environment may be made in your .cshrc.custom file.

How do I set up my UNIX account to run other software in the Department?
Every time you log on, the file .login. Every time you open a window or create a shell, the file .cshrc is read and executed. The following are the standard .login and .cshrc distributed by the Department.

Edit your .login file to look like this:

source /usr/local/etc/login

source /usr/local/etc/cshrc

How do I set up my Windows NT/2000/XP machine to be able to access AFS files?
First, go to the OpenAFS website at:  http://www.openafs.org/ and download the latest OpenAFS client for Windows.

Next, click on the client you downloaded to begin the installation process.

After installation is complete, you'll have to configure the client. For the Cell Name, enter "cs.pitt.edu".

Next, click on the AFS Cells tab and click on the "Add" button. In the Cell Name field, enter "cs.pitt.edu".  Then, add the following servers:

afs01.cs.pitt.edu
afs02.cs.pitt.edu
afs03.cs.pitt.edu

Next, go to the Control Panel and click on the AFS Client applet. Turn on Logon Authentication so that when you log onto the Windows machine, you will automatically be given a token. (Note: Your Windows username must be the same as your AFS username and your Windows and Unix passwords must match for this to work!)

Next, click on the Submounts tab and click "Add".  For your account, you'll want to add the following entry:

Share: myusername
Path: \afs\cs.pitt.edu\usr0\myusername

It is now time to map an AFS drive to a drive letter. You do this by using the NET command. Open up a Command Prompt. The syntax for the NET command is NET USE drive-letter: \\nt-machine-name-AFS\myusername

For example, if we want to map drive M: on a machine named "maestro" for myusername it would look like:

net use m: \\maestro-afs\myusername

This is accomplished using the same NET command as above but replace myusername with 'all'.

The standard drive mappings that we use on the departmental Windows machines are:

• M: - the currently logged on user's home directory
• N: -  the AFS root cell

How do I verify if the message I got about a virus is true or not?
You can check the Hoax Buster's Web site if you suspect a hoax (not a true virus).  Also the Norton Antivirus home page is an excellent place to check on the latest virus threats.

Why do I sometimes get 2 requests for passwords when logging into Linux?
That's the behavior of the new PAM module under Linux. If your AFS password is incorrect, it then prompts you for your local password.

PAM is the Pluggable Authentication Module. It's now supported on a number of architectures, such as Solaris 2.6, HP-UX 10.2, and Linux. You can look at the The Linux PAM web page.

How can I look and edit MS Office (Word, Excel, etc) files in the UNIX machines?
StarOffice is installed in /usr/local/contrib/bin; this should be in your $PATH. To invoke StarOffice type 'soffice' at the command prompt.

How can I add to my $PATH variable?
At the command prompt type the following

setenv PATH ${PATH}:<path-to-be-added>

How can I install programs (for everyone to use and not using my own disk quota) in the UNIX machines?

1. Send a request to tech@cs.pitt.edu and request to be added to the contributor's list.  Be sure to specify what you want to install in this e-mail!
2. Download the software into the contrib directory, untar, etc.
3. Install the software for as many platforms as possible.  Here is a list of the platforms we currently support:

        - any of the Elements machines for Red Hat Enterprise Linux
        - blitz.cs.pitt.edu for Solaris 9
       
4. The install procedure is as follows:

1. There is a directory under /usr/local/contrib that you add the software to.  Unzip the software and add the sources to /usr/local/contrib/XXX/src and add the binaries to /usr/local/contrib/bin (NOTE:  No XXX in the bin directory, it is pure /usr/local/contrib/bin).
2. Write a documentation or README file that will reside in the /usr/local/contrib/XXX directory.  This should include the paths and the variables that the software requires.  If the usage is complicated, a script should be created to facilitate using the program.
3. Install the man pages in /usr/local/contrib/man.

Thanks again for volunteering!  We truly appreciate it!  Also, let tech know if you have any problems.

How do I create a symbolic link in UNIX?

ln -s <path-to-original-location> <path-to-link-destination>

How to have email forwarded to another address?

Suppose you ewant your email forwaded to other_address@wherever.com. Simply create a file in your home directory called ".forward".   In it, put:

<your-CS-username>, other_address@wherever.com

fs sa ~ mailserver rl

The alias database can be displayed by saying

ypcat -k mail.aliases

The department is running SpamAssassin on all incoming mail.
For steps you need to do to enable it for your mail, read this HOWTO.

To unspam/de-spam a message that has been labeled as SPAM by SpamAssassin, follow the instructions given below:

1. Take the "*****SPAM***** " out of the subject line.
2. Delete the Content-Type: header line.
3. Take the "X-Spam-Prev-" out of the X-Spam-Prev-Content-Type header line.
4. Delete the remaining header lines that begin "X-Spam-".
5. Delete all of the lines that begin "SPAM: ".

For the 5505 and 5502 labs, there is a method for turning off network access to the internet in general, or to limit traffic to just within the department.

Visit http://labaccess.cs.pitt.edu/

DISKS & FILES

What do I do if I need more disk space?
User accounts are initially created with a default disk quota. Occasionally more disk space may be needed for data intensive applications. If you need more disk space, you should send e-mail to tech requesting more space and why you need it.

The AFS command "fs lq" will tell you your disk quota (in 1-Kbyte blocks), how many of those blocks are currently used, the percentage used, and the percentage of space used on the disk partition that you share with other users. Note that this command will tell you this information about the AFS volume that your current working directory resides in. If your username does not appear in the volume name listed with this command just "cd" to your home directory.

The UNIX command "du" will give you a block count and an idea of how much space is being used by a individual directories and files. See the man page for this command for the particular workstation you are on.

About your Windows profile space...

How are my files set up?
The Computer Science Department uses the Andrew File System (AFS) to manage user accounts. This distributed file system allows user accounts to be accessed from any department machine as well as any other machine located throughout the world provided that machine is running AFS. A user does not need an account on remote sites to access AFS volumes and the files that they contain provided the appropriate AFS access rights are granted for these directories. If a user does have an account at another AFS site such as the University's CIS department, these files may be accessed from this department's machines without having to log into University machines (see How do I access other AFS cells? below).

When you log into a UNIX machine, your current working directory is set to your home directory. Your home directory and all files and subdirectories are stored in what is called an AFS volume (or simply volume) which can be displayed by the AFS command "fs lq".

A user's home directory is initially set up with two subdirectories called "public", and "private", and a symbolic link to a backup directory called "Backup". The AFS access rights for each of these files is appropriately set and should not be changed. The public directory is world readable and is intended for sharing files with others and holding the user's World Wide Web home pages. The private directory is intended for personal files that a user wishes to protect from world-wide and local users.

A user's home directory can usually be referenced in UNIX shell commands by the syntax "${HOME}" or "~", the tilde character; the former syntax is the preferred method when referencing the home directory from shell scripts.

Access to particular files within a user's home directory is controlled by AFS access rights. The usual UNIX mode settings controlled via the UNIX command "chmod" are meaningless when the file or directory is located within an AFS volume.

How do I control access to my AFS files?
Access to individual directories in your home directory by you and other users is managed under AFS by way of Access Control Lists (ACLs). ACLs are maintained for each directory in your volume and are under your control. Directories in your volume are still created with the UNIX "mkdir" command, but access is controlled via AFS. The ACL for a newly created directory inherits the ACL of the parent directory.

An ACL has two parts: a user or group name and the access control rights. The user/group name and the "rights" are separated by a space. The seven access rights are indicated by letters or, alternatively, one of four "shorthand" words used to represent more frequently used subsets of these rights:

Access Control Rights		Shorthand Notation
r: read	d: delete	read = rl
l: lookup	w: write	write = rlidwk
i: insert	k: lock	all = rlidwka
a: administer		none = removes entry

The AFS command used to set and modify ACLs is the "fs" command. Limited help is available on the man page for this command. A synopsis of these commands may be displayed by typing "fs -help", "fs listacl -help", and "fs setacl -help".

EXAMPLES:

1. List ACL for current working directory:
                   fs listacl
2. List ACL for the directory dir:
                   fs listacl dir
3. Give user john all rights to dir:
                   fs setacl dir john all
4. Revoke all rights to group system:anyuser (The following command should be used when creating a new mail directory.):
                   fs setacl Mail system:anyuser none
5. Provide user john with write access and user jane with read access to all files in the current working directory:
                   fs setacl . john write jane read (or fs setacl . john rlidwk jane rl)

 

find . -type d -exec fs sa {} foo baa \;

If you discover the error the same day (i.e. before the next nightly backup is done), you can quickly recover the file yourself. Each weeknight, a copy of all files within your AFS volume is backed up to a separate volume pointed to by the symbolic link called "Backup" in your home directory. You may use the UNIX command "cd" to get to this volume and its subdirectories which is a mirror of your home directory for the previous day.

Once you locate the file in question, use the UNIX "cp" command to copy this file to the appropriate spot in your home directory. See the "cp" man page for the system that you are logged onto; there are slight variations between UNIX platforms.

It is faster to recover files yourself from the ${HOME}/Backup directory whenever possible since it does not involve the staff loading tapes when time permits.

I can't rlogin from a system listed in my '.rhosts' file. Why not?
The concept behind the '.rhosts' file is that there are host machines in the network that can be trusted, and that login and rsh requests between these machines do not need a password. Unfortunately, this feature has become a major security loophole in UNIX systems.

Using AFS, the Computer Science department systems work as follows. When you login to a compute server, the login process needs to access your home directory to get your initialization files. Access to your files is provided by the AFS Protection server, which will let login read your files only if it has received a token from the AFS Authorization server. However, the AFS Authorization server will not provide a token without a password. Since none was provided by rlogin using the .rhosts file, login completes using default settings. In either case, you will only be able to read your public files and you will not have any write authority.

When I do an "ls -l" on the '/afs' directory, my terminal hangs. Why?
AFS provides a file system which allows files to be distributed anywhere in the world. The subdirectories of /afs, called cells are actually pointers of sorts to other locations around the world. The /afs directories provide access to files contained within these cells according to the same AFS access rights discussed above.

The information that you request with the -l or -F option when invoking the ls command is actually kept at these remote locations. These specific options will cause AFS processes to contact remote AFS processes to gather statistics about the relevant directory entries. Depending on the number of locations contacted, their distance from the local cell (in this case, cs.pitt.edu) and the random occurrence of network failures, it can take a very long time to complete the commands: "ls -l /afs" or "ls -F /afs".

If you have inadvertantly, or otherwise, executed these commmands on remote /afs entries, you can check which ls command you are using by the commmand "which ls" at a later time - you may have it aliased to one of these.

To try and abort this command is at times difficult. You can try typing ^c (control-c) to interrupt this command or, if this does not seem to work, try typing ^z to suspend this command. If this works, your prompt will come back and you will be able to type the jobs command to see the suspended job. Then type "bg" to run this command in the background, followed by "kill %" to interrupt the most recent job put in the background. This may take a moment or longer; kill will send a terminate signal to the ls process which may be too busy at the moment to catch this signal and respond right away.

If you really want to use these forms of the ls command on remote AFS sites, it is usually less frustrating to limit your inquiries to one or a few cells.

How do I access other AFS cells?
You do not need to have a user account at another AFS site (cell) inorder to access data stored at the sites listed in /afs. Simply follow the directory hierarchy using the UNIX cd command for the chosen site. It may take a while for the data to be transferred from the remote site for this command to complete. The usual UNIX commands for reading and copying files apply, but you will only be able to access files that are AFS publicly readable as granted by the owner of the file(s).

If you do have an account at another cell, as many of us do from previous undergraduate AFS sites, or currently at this University's CIS department, you do not need to directly log into the University's machines to gain full access to your files in this account. For example, if you have an account at Pitt CIS (another AFS site) you can gain full access rights to your remote files by authenticating with the remote cell site; in this case "pitt.edu". To do this, the AFS "klog" command is used. You will need to know the name of the remote cell, your username for the remote account, and you will be prompted for your remote password:

klog -principal username -cell pitt.edu

NOTES. The AFS command "tokens", will tell you what cells you are currently authenticated for. The AFS command "unlog -cell pitt.edu" will discard the token for access to the specified cell; careful... not specifying a cell will discard all tokens including access rights to your home directories. If this happens just klog again with no parameters; your current login cell is used by default.

I frequently have problems accessing files after I have been logged in for a long time. Why?
When logging into an AFS site such as the Computer Science Department, you are authenticated (i.e. verified) as a user in this department's AFS cell. The authentication process associates a token (also referred to as a ticket) with your login process. The token you receive at each login is good for a period of 25 hours. If you are logged in for more than this time, your token automatically expires and you will not be able to access files in your home directories that are not publicly readable/writeable. To get a new token, issue the AFS command "klog"; you will be prompted for your password and reauthenticated.

How do I clean up my account to get more space (core files specifically)?
Core files are dumps of memory that are kept in a file for debugging purposes when a program crashes. Typically you do not want these on your directories, since they are rather large files. You can periodically run a command that finds and removes the core files:

find ~ -name core -exec /bin/rm {} \;

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