As we said, UNIX is a multi-user
environment. Thus, in order for UNIX to provide you with your
own private environment, you must identify who you are.
To do so, you must provide a "login" name
and a "password" when you want to log into a UNIX machine. The "login" name identifies which of the many
users you are and the password assures that you really are who you
say you are.
password is something like locking your keys in the car. You are
pretty much stuck. You will have to have the systems administrator
assign you a new one.
Thus, all UNIX sessions begin with a login
prompt. This prompt will most often simply query you for a login
name such as in the following case:
In the image above, I used COMNET, a Windows-
based Telnet client, to log into a UNIX server named
188.8.131.52. Notice that the server identifies itself as using
Red Hat Linux, a variant of UNIX and prompts me to type in my
There are many ways to use a computer
running UNIX. You can login directly by turning the UNIX machine
on and using its keyboard, or you can login remotely (from another
computer networked with the computer running UNIX) using a
networking program like telnet, ftp, rlogin, etc.
For the most part, web technicians will
use Telnet to login to a remote UNIX web server, possibly provided
by an Internet Service provider. Likewise, they will use ftp
to transfer files from their local machine to the UNIX machine.
You can easily pick up
a shareware or freeware Telnet or ftp program for whatever type of
computer you use by pointing your web browser to
When you see the login prompt, you should
simply type in your login name (which you should have gotten
when you got your account to the UNIX machine). When you do so, a password
prompt will appear. As you see in the image below. Simply type
in your password.
Notice that whereas the characters you type
for the login name will echo to your monitor, the characters you
type in for the password will be invisible. This is to prevent
people from getting your password by looking over your shoulder.
It is crucial to remember that though login names are common
knowledge, passwords should be kept confidential.
It is crucial that you
take care to choose a good password and to take care to protect that
password. If someone gets a hold of your password, they can use
it to masquerade as you. As you, they can do anything from being
annoying to committing crimes as you.
The directions for the care
and feeding of good passwords can be found in many books and websites
but at very least, you should choose a password that does not
exist in any dictionary and which incorporates both capital and
lower case letters, numbers and perhaps a punctuation mark or
Also, keep in mind that UNIX is a case-sensitive
OS which means that a capital "A" is considered different from a lower-case
"a". Thus the loggin "Selena" is a different account from "selena". Similarly,
if your password is "PASSWORD" and you type in "password", you will not be granted
If you have entered a correct login id and
password, you will be given access to the system. Typically, you
will be presented with a shell prompt through which you can issue
commands such as in the following case:
Each shell has several available prompts. So if you do not see the
dollar sign prompt ($) as shown in the image below, you might
see a "%", "!$", "#?", or ">" . Don't be surprised if your
command line looks a little different than the example. They all
work the same.
We are going to talk a great deal more about
what you can do once you are logged in. However, before we move on,
you should know how to log out when you are done.
Logging out is achieved by typing "exit"
at the command line and hitting return.
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