A password is a sequence of characters that is secret and only known to the owner. On most systems this is the only level of security the user has since usernames are very often used for other services such as email.

Passwords should be memorable but not guessable by others. Passwords should be a mixture of characters and numbers, called alphanumeric. However, Unix systems also allow punctuation characters to also be included in passwords.

Your Password

Your password is your only level of security for your account- PLEASE DO NOT:

  • Give your password to anyone else, or write it down.
  • Use a password that could be easily guessed by someone else (e.g. your surname plus a number)

You are provided with a password when you register with a Unix administrator. This password is expired, or out-of-date, so that a new password has to be entered the first time you log on to your Unix system.

However, on some systems your new password will expire every, say, three months and you will have to change it again. It is good practice to change your password regularly.

Passwords are changed using the passwd command as follows:

Type: passwd
Press: <Return>
Response: Old password:
Type: your_old_password
Press: <Return>
Response: New password:
Type: your_new_password
Press: <Return>
Response: Re-enter new password:
Type: your_new_password again
Press: <Return>


New Passwords

On Unix systems new passwords must be at least six alphanumeric characters in length and contain at least two alphabetic characters and at least one numerical character within the first eight characters (special characters can be used).

NOTE: Passwords are case-sensitive so Merlin4 and merlin4 are two different passwords.

If an illegal password is typed one of the following responses may appear:

    For a password not containing correct number of alphanumeric characters:

        Password must contain at least two alphabetic characters and at least one numerical or special character

    For a password that does not contain at least 6 characters:

        Password is too short - must be at least 6 digits