Duke University
Center for the Study of Aging and Human Development

Computing & Statistics Lab

Chapter 2 - Getting Connected to the geri systems: Joining the Party

ssh and telnet -

     The purpose of ssh (Secure SHell) is to allow you to establish an
interactive session on another computer so that you can run programs with
text interfaces that are offered by that computer. The computer at which
you are sitting must already be on the Internet either via a direct 
connection, such as in your office, or through your ISP. It is a secure
shell because your username, password and all of the data it transfers is
encrypted, thus it cannot be read even if it is captured off the network.
Duke students and staff can download an ssh client for their pc or
Macintosh from http://www.oit.duke.edu/site/ or from
http://www.duke.edu/~ieisen/pc_software.html. When you run the ssh
program, tell it to connect to rubin.geri.duke.edu.

     Use telnet only if the computer you are on does not have an ssh
program. The syntax for using telnet is 'telnet ipaddress'. For example,
to run programs on the geri computer known as rubin, you would issue the 
command 'telnet rubin.geri.duke.edu'. You will then be prompted for your
username and password. At the end of your session, type 'exit' at the 
UNIX prompt. You may also have to exit from the telnet program itself.

     If you are connecting from a pc, you will be running a terminal
emulator when you issue the telnet command. There is one very important
parameter to set. You must tell the program what type of terminal to
emulate. Any of the DEC VT terminal types will work on the geri systems,
the most common being the DEC VT100.

     You will not find yourself at the 'telnet>' prompt often, but, if you
do, you can type 'help' to get more information.


sftp and ftp -

     This is the secure file transfer protocol. If you are already using
an ssh client on your pc for an interactive session, look under one of the
main menu items for a file transfer function. Again, you can take
advantage of the added security of knowing that your data is encrypted.

     For regular ftp, the syntax is similar to telnet - 'ftp ipaddress'.
If you had a file on your computer that you wanted to transfer to rubin,
it would be 'ftp rubin.geri.duke.edu'.

     After logging in you can use the usual UNIX commands for moving from
one directory to another (eg. 'cd' and 'pwd') and for listing the files
in a directory (eg. 'ls'). Once you have determined that you are where
you want to be, you can 'put filename' to transfer a file from your local
computer to the remote computer, or you can 'get filename' to go the other
direction. Use the command 'quit' to end your ftp session.

     What is most important when transferring files is knowing whether
the file is ASCII (text) or binary. Use the UNIX command 'file filename'
to make that determination. By default at the start of your ftp session,
you will be in ASCII mode. To send a non-ASCII file, issue the command
'binary' at the 'ftp>' prompt. You can  always issue the command 'type'
at the 'ftp>' prompt to see what mode you are in.

     A little more on file types. When we talk about ASCII (text) vs.
binary, we are not referring to what the contents of a file look like
on your monitor. These file types are two of the formats in which your
computer's operating system stores files on disk. Typically a text editor
(vi, pico) will write ASCII files. Typically a wordprocessor or
spreadsheet program will write binary files.

     More information is available by typing 'help' or '?' at the 'ftp>'
prompt.

X Windows -

     Some of the UNIX programs, such as SAS, S Plus, StarOffice and
Netscape have a graphical interface. They are written to use the
X Windows protocol. For you to take advantage of these programs, you
need an X Windows terminal emulator. This software is available from
Duke's site license web site at no charge to the Duke departments.

Logging in -

     When you see the 'login:' prompt from the specified geri system
computer enter your username. When you see the 'Password:' prompt, enter
your password. Unauthorized users are not allowed to access the geri
systems. You will know if you are authorized if you have been given a
username and password by the geri system manager.

Passwords -

     Selection of a hard-to-guess password for your UNIX account is
very important.  The UNIX computers at the Center for Aging are
connected to the Internet, which means that besides giving us
access to tens of thousands of computers around the world,
hundreds of millions of people have access to our computers!  The
primary line of defense against online computer vandalism and data
theft is through the use of secure passwords.  If a sophisticated
hacker on the network can guess your password, he/she can access
your account and possibly compromise the entire system.

    To change your password, login to UNIX by typing your account
name (user name) and password.  Then, at the UNIX prompt
('user@computer>'), type the command "passwd".  You will be
prompted for your current password. Enter it, and then you will be
prompted for your new password. Enter your new password. You will be
prompted to confirm it by entering it again. As a security precaution
the system never displays your password when you are entering it.

    Please use the following criteria in selecting a password:

	- minimum of 8 characters long
	- mix from the following character types
	    - upper case letters
	    - lower case letters
	    - digits
	    - punctuation marks and other special symbols
	    - spaces and tabs
	- do not use parts of your name, phone number, words
	  related to Duke or Durham, and especially not
          dictionary words, either English or foreign;
        - try to make it sound like something meaningful to
          you so it is easy to remember; some examples, but do
          not use these now that everyone has seen them,
          Pizza4Lunch, L3tM3iN (Get it? let me in; 3=backwards E)

    We run a program once a month that tries to guess passwords
using the same methods that "crackers" on the network use to gain
access to computer accounts.  If this program guesses your password,
it will automatically send you an email notification with a request
that you change your password.

    If you ever forget your password, we cannot tell you what it
is, because passwords are stored on the system in an encrypted
format. We can only delete your password, and let you set a new
one.

     Duke policy states that users should never share their password
with anyone else unless absolutely necessary, and that the password
should be changed immediately after the other person no longer needs
it. You should also change your password if you even suspect that
someone else has discovered it.

Logging Out -

     To end your session enter the command 'exit'. You will then be
logged out, but you might still need to exit from the terminal
emulator that you used for communicating with the geri system.

Remote Access -

     If you wish to connect to Duke computers and the internet from your
home, you must subscribe to an Internet Service Provider (ISP). People 
affiliated with Duke can receive discounted broadband, high speed access. 
Read the following web site for more information. 
http://www.oit.duke.edu/remote_access/