Finding Your Way Around a Unix system

This section serves as an introduction to using the Unix operating system. The commands covered are pretty much standard in most flavours of Unix. Therefore these notes are appropriate for when you login to a University system and your own Linux machine at home.

Unix is a command driven¹² system. That is, you type a command to make the system perform a task. Those familiar with the MSDOS system will recognise some Unix commands. A lot of MSDOS commands, as well as the directory structure, were derived from Unix.

login

A Unix computer system can be shared by many users simultaneously. As a result of this, you must login to your own private account before you can use the computer. When you connect to a Unix system, probably by using your telnet program, you should see something that looks like:

Trying 129.180.11.17...
Connected to turing.une.edu.au.
Escape character is '^]'.

Red Hat Linux release 7.2 (Enigma)
Kernel 2.4.9-13enterprise on a 4-processor i686
login:

See Section 4 on how to get to this login prompt. See also Section 2 for how to get a username and password on UNE systems.

If you type the correct username and password, you will be logged onto the computer:

Red Hat Linux release 7.2 (Enigma)
Kernel 2.4.9-13enterprise on a 4-processor i686
login: fflintst
Password:
Last login: Wed Nov 17 20:49:46 from digimodem-1.une.edu.au
turing %

The string turing % is called the shell command prompt. When you see this, the system is ready to accept commands. The command prompt can be configured to contain almost anything and so may vary in appearance from system to system.

passwd

One of the first things you might want to do after you initially login, is to change your password to something you can remember. The command to do this is passwd. In the same way as when you logged into the computer, your password will not show up on the screen.

To use the passwd command, type passwd and then enter your old and new passwords at the appropriate prompts.

turing %  passwd
Changing password for fflintst.
Old password:
New password:
Retype new password:

Choosing a good password is important. Even if you think your files are not important, a poor password will allow your account to be used as a base to get to other accounts. Good passwords have the following properties:

• Five to eight characters in length.
• Not a dictionary word or proper noun.
• Not an anagram of your name or login name.
• Contain at least one numeric or punctuation character.
• Have a mixture of upper and lowercase letters.

The passwd program tries to check for some of these conditions when you enter a password and so may reject your new password. If this happens you will need to think of a new password.

logout

To complete a login session, type logout. The computer may print a fortune, a few statistics and then exit from your telnet program or go back to wherever you came from.

turing % logout

Computers are not intelligent.  They only think they are.

Connection closed by foreign host.