Minimum Password Length of 6 characters

Hi Linux gurus, can anyone tell me how to set a minimum password length of 6
characters in Linux? 

Gilbert

****************************************************************************
*******************************************
Express yourself in real time with Vodafone's MMS

Send and receive colour pictures from your MMS mobile phone. With Vodafone's
MMS your can combine images, audio clips and text in one single message and
send them to any other MMS phone or email address.  For MMS activation and
further details contact 247 or visit any Vodafone Retail Outlet.

As a special introductory offer Vodafone's MMS service is FREE to all
Vodafone customers.

Visit www.vodafone.com.mt & have fun with Web2MMS!

****************************************************************************
*******************************************