4.1 User logins, password and logouts

To ensure security and organization on a system with many users, UNIX machines employ a system of user accounts.
The user accounting features of UNIX provide a basis for analysis and control of system resources, preventing any
user from taking up more than his or her share, and preventing unauthorized people from accessing the system.
Every user of a UNIX system must get permission by some access control mechanism.

Logging in
Logging in to a UNIX system requires two pieces of information:
1) A username, and
2) a password.
When you sit down for a UNIX session, you are given a login prompt that looks like this (depending on the flavors
of UNIX OS you are using):

    login:
Type your username at the login prompt, and press the return key. The system will then ask you for your password.
When you type your password, the screen will not display what you typed.

Your username
Your username is assigned by the person who creates your account. Your username must be unique on the
system where your account exists since it is the means by which you are identified on the system.

Your password
When your account is created, a password is assigned. The first thing you should do is change your password,
using the passwd utility.
To change your password, type the command  passwd after you have logged in. The system will ask for your old password, to prevent someone else from sneaking up, and changing your
password. Then it will ask for your new password. You will be asked to confirm your new password, to make sure
that you didn't mistype. It is very important that you choose a good password, so that someone else cannot guess it.
Here are some rules for selecting a good  password:
 

• Do not use any part of your name, your spouse's name, your child's name, your pet's name, or anybody's name.
• Do not use any backward spellings of any name, either.
• Do not use an easily-guessable number, like your phone number, your social security number, your address, license plate number, etc.
• Do not use any word that can be found in an English or foreign-language dictionary.
• Do not use all the same letter, or a simple sequence of keys on the keyboard, like qwerty.
• Do use a mix of upper-case and lower-case letters, numbers, and control characters.
• Do use at least six characters.

Excercise
    Change your passord after you login the first by typing
       passwd [Enter]

Logging Out
       It all depends on the OS you are running. Most Uinces have a nice GUI to let you click a button to logout. Otherwise
just use exit command
 

3.2 Telnet and ftp

Due to security problems, we no longer allow telnet or ftp connections to any computers at UTMB.  Use Secure Shell Protocols ssh or scp!
Telnet
Telnet is a program that allows you to log into your user account on a remote UNIX server.
Telnet provides a command line, text-only type of connection.  A basic Telnet program is built into Windows, Macintosh, and Unix computers. You can also get Telnet programs as freeware or shareware that expand the functionality of the basic Telnet. All work in a similar maner: they allow you to log into your remote unix computer account and directly access your files using UNIX commands so you can work at home. By typing

     %telnet vishnu.utmb.edu [Enter]
 
then you will see something like:
Trying 129.109.73.47...
Connected to vishnu.utmb.edu.
Escape character is '^]'.
 

IRIX (vishnu.utmb.edu)

login:

                 IRIX Release 6.5 IP30 vishnu
                Copyright 1987-2002 Silicon Graphics, Inc. All Rights Reserved.
                 Last login: Wed Sep 04 11:13:57 CDT 2002 by yuan@planck.utmb.edu
                 on your screen.
 

               ftp

                The ftp program lets you contact a remote server computers to initiate remote  file transfers.
                All computers do not implement the server function. Typically, UNIX systems have both the client programs
                 and the server function (although the server may be turned off or restricted by the system manager for
                 security reasons), allowing two-way connections between UNIX computers, initiated at either end. Desktop
                 computers such as Windows PCs and Macintoshes typically only have the client programs, and can initiate
                 connections to UNIX servers, but not to other desktop computers.

       ssh login
                 %ssh gibbs.utmb.edu

                 %ssh -l username gibbs.utmb.edu     (using a different username on the remote computer)

       scp

                The scp program lets you contact a remote server computers to initiate encrypted remote file transfers. All computers do not implement the server function. Typically, UNIX systems have both the client programs and the server function (although the server may be turned off or restricted by the system manager for security reasons), allowing two-way connections between UNIX computers, initiated at either end. Desktop computers such as Windows PCs and Macintoshes typically only have the client programs, and can initiate connections to UNIX servers, but not to other desktop computers.

                %scp plaster powert@gibbs.utmb.edu:~home
        (transferring a file called plaster to gibbs in home directory powert, and logging in as powert)
        Note that in this example you must be in the local directory of the file plaster to send this file

                %scp plaster powert@gibbs.utmb.edu:/home/people/powert
  (transferring a file called plaster to gibbs in /home/people/powert, and logging in as powert)

                %scp pl* powert@gibbs.utmb.edu:~home
(transfer all file beginning with pl to gibbs in /home/people/powert, and log in as powert while doing this)

                %scp powert@gibbs.utmb.edu:~home/APE1/results/min09_B.pdb .
(transferring a remote file min09_B.pdb from gibbs belonging to user powert in $home/APE1/results to the current local directory)
Note that you MUST know the location and the EXACT spelling of the file you would like to transfer in advance, the wild type '*' does not work when transferring files from a remote host to a local host.

Also, you must have write permissions of a directory you are transferring to in order for this to be a successful transfer.

     Using Window OS (XP)
                If you are using window XP and would like to work on a unix server you can do so via using XP based ssh                   and scp software. Some of those are free and can be downloaded from the internet. Below I list two                       free client ssh and sftp software for you to download if your PC does not have them.

    Download sites

                  1) Putty - for ssh (good and easy to use) http://www.chiark.greenend.org.uk/~sgtatham/putty/
                  2) WinSCP (good and easy to use) http://www.download.com/3000-2160-10256215.html