To ensure that new passwords are strong, configure Linux to run cracking tests on new passwords and allow only strong passwords to be use. This is done by adding the following lines to /etc/pam.d/passwd:
* password required pam_cracklib.so retry=3 minlength=10
pam_cracklib.so is a file. You may need to give the full address of the file, such as /lib/security/pam_cracklib.so (the location on Mandrake 9.0). The "retry=3" means the user is allowed three attemtpts to create a qualified password. "minlength=10" sets the minimum length of the password to 10 charactes. You can adjust the retries and minlength as needed.
* password required pam_unix.so use_authtok md5
This directs the system to use MD5 password hashes instead of the default DES hashes. Again, you may need to provided the full address to the file, such as /lib/security/pam_unix.so on Mandrake 9.0.