Remember the following two principles
Protect your password.
Don’t write down your password - memorize it. In particular, don’t write it down and leave it anywhere, and don’t place it in an unen-
crypted file! Use unrelated passwords for systems controlled by different organizations. Don’t give or share your password, in partic-
ular to someone claiming to be from computer support or a vendor. Don’t let anyone watch you enter your password. Don’t enter your
password to a computer you don’t trust or if things "look funny"; someone may be trying to hijack your password. Use the password for a
limited time and change it periodically.
Choose a hard-to-guess password.
passwd through the calls to the pam_cracklib PAM module will try to prevent you from choosing a really bad password, but it isn’t fool-
proof; create your password wisely. Don’t use something you’d find in a dictionary (in any language or jargon). Don’t use a name
(including that of a spouse, parent, child, pet, fantasy character, famous person, and location) or any variation of your personal or
account name. Don’t use accessible information about you (such as your phone number, license plate, or social security number) or your
environment. Don’t use a birthday or a simple pattern (such as "qwerty", "abc", or "aaa"). Don’t use any of those backwards, followed
by a digit, or preceded by a digit. Instead, use a mixture of upper and lower case letters, as well as digits or punctuation. When
choosing a new password, make sure it’s unrelated to any previous password. Use long passwords (say at least 8 characters long). You
might use a word pair with punctuation inserted, a passphrase (an understandable sequence of words), or the first letter of each word in
a passphrase.
These principles are partially enforced by the system, but only partly so. Vigilence on your part will make the system much more secure.