3.4. Changing your Password

3.4.1. Choosing a password

Having a secure password is very important, especially on a system like ours. Secure means that nobody except you knows your password, and that nobody can guess your password. In order to accomplish this, the system is set up that once you set your password, nobody can read it, not even the administrator.

Why does it really matter? Well, even if you don't care if someone else reads your mail, you have many privileges as a tentacle.net user. If someone got access to your account, they could do many malicious things, including breaking into other computers. The point is that the whole system's security is compromised if someone gets into your account, even if you yourself don't have much secret stuff in there. Although the system is designed to provide some protection against such an event, it's best to prevent such things completely. (This is, in part, why everyone's always telling you never to give your password to other people.

Choosing a secure password can be a little bit difficult. A good password is at least 5 or 6 characters long, is not based on any real words, and has a mix of letters, numbers, and punctuation marks. Doing all that and still remembering the password can be tough, so there are a number of mnemonics to help you create and remember a good password.


Passwords are case-sensitive, meaning you need to type upper- and lowercase characters exactly as first set.

One method is to make up a phrase or sentence that you can remember, then to take the first letter or number of each word and make that your password. For example,

Our planet, Earth, is the 3rd planet from the sun.

would become


Of course, you can also just use the entire phrase as your password, if you don't mind typing it each time.

Another method is to use the apg(1) program, available at the command line (see Chapter 3, The UNIX Command Line). It will generate a set of six possible passwords every time it's run. Its output appears something like this:

chaos[1] % apg
chaos[2] % 

3.4.2. Setting your password

Once you've decided on a new password, connect to the server using SSH to get a command prompt (see Chapter 3, The UNIX Command Line). At the prompt, type passwd. You should see output like the example below:

chaos[1] % passwd
Changing local password for username
Old password:
New password:
Retype new password:
passwd: updating the database...
passwd: done
chaos[2] % 


When you type your password, nothing will show up on the screen. This helps keep people from looking over your shoulder and seeing your password.