Using an Ubuntu 12.04 or a Red Hat Enterprise Linux Desktop 6 for Desktop, how can we force the users to change their LUKS passwords at every 90 days? 
How to force the change of the LUKS password in every 90 days?
luks
There's not much point in doing this. Ordinarily, the point of changing passwords regularly is that if someone else has learned your password, you limit how long they can use it. But a LUKS password is used to decrypt the LUKS volume's master key, the one that's actually used to encrypt the data, so if someone learns your password, they can use it to get that master key. Changing your password doesn't change the master key  remember, it's the key used to actually encrypt the data; changing it would require re-encrypting the entire drive  so you're not depriving the attacker of access to the drive.(Note, this assumes a technically-sophisticated attacker, someone able to find or write a program for unlocking a LUKS volume using the master key directly rather than a keyslot passphrase. Changing passwords might help against someone who only knows how to interact with the normal LUKS password prompt  but against someone like that, you probably don't need disk encryption at all.)