The pam_cracklib.so module checks the strength of passwords. It performs checks such as making sure a password is not a dictionary word, it is a certain length, contains a mix of characters (e.g. alphabet, numeric, other) and more. The following are definitions of the pam_cracklib.so options. try_first_pass - retrieve the password from a previous stacked PAM module. If not available, then prompt the user for a password. retry=3 - Allow 3 tries before sending back a failure. minlen=14 - password must be 14 characters or more dcredit=-1 - provide at least one digit ucredit=-1 - provide at least one uppercase character ocredit=-1 - provide at least one special character lcredit=-1 - provide at least one lowercase character The settings shown above are one possible policy. Alter these values to conform to your own organization's password policies. Strong passwords protect systems from being hacked through brute force methods.
Edit the /etc/pam.d/common-password file to include the appropriate options for pam_cracklib.so and to conform to site policy: password requisite pam_cracklib.so try_first_pass retry=3 minlen=14 dcredit=-1 ucredit=-1 ocredit=-1 lcredit=-1