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Introduction to UNIX for Web Developers
Logging In  
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.

Forgetting your 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:

[LOGIN PROMPT]

Note:
In the image above, I used COMNET, a Windows- based Telnet client, to log into a UNIX server named 163.18.14.41. Notice that the server identifies itself as using Red Hat Linux, a variant of UNIX and prompts me to type in my login name.

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 shareware.com

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.

[PASSWORD PROMPT]

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.

Warning:
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 two.

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 access.

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:

Note:
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.

[PROMPT]

Logging Out
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.

[Exit Command]

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