I use the "chage -d user " to force the user change their password , however , there are some restriction for the new password eg. can't a dictionary word , can't too simple , can't used previously ( it should be the RH default rules ) but some users reported that it is too many restrictions, how can I disable these rules so that the users can use any password ? thx.

If you're running any system that needs integrity, I'd recommend sticking to the rules. Yes, it's annoying at first, but users soon get used to it. They are there for your benefit, after all. Instead of removing them, you should print up a list of examples and distribute them to your users. In most cases, just adding a number or underscore in a "normal" password will solve their problem. There is an option to disable it, but you should consult whoever's responsible for the system--or the company owner, before disabling it. Make sure you get permission in writing too, or this will blow up in your face.

You can simply disable the password timeouts as well, but I'm a little hesitant to make this easy. After all, passwords are there for a reason. Your 'info' files should contain the appropriate information. Sorry.

Your users might not like the password terms you've placed on your system but that just ensures the security of the machine. You should educate your users that strong passwords and forcing this upon them only ensures the better security of the server itself.
Your users can complain but you should make it aware also to them that its not their choice. Your job is to secure your network and machines, and that is what your doing.

Changing passwords is a major pain.
The stupid windows setup I have to use at work forces us to change our passwords every 2 weeks.
I have 46 (at last count) passwords/door entry codes and whatnot to remember. Now it is new passwords to remember every 2 weeks as well.
So what do we all do?
Choose stupid passwords: January ... February... One... two...
This isn't secure, it's driving the users insane.

Solution: Let the users choose a password, make sure it is an awkward one, AND THEN LET THEM KEEP IT.

Rant OFF.

thx replies, but as I know there is a function of "pam" , that can control the password restriction , and also similiar function in webmin , could suggest how to set it ? thx.