Change encrypted swap passphrase ?

Hi.
I’ve chosen to encrypt my swap partition while I was installing opensuse 11.3 on my PC.
I want to know how I can change its password(passphrase)?

Thank you

Using google often will give you a solution way faster than asking in a forum. Just a hint.

How to Change a LUKS Password | eHow.com

Instead of ‘sudo’ I recommend becoming root the regular way (‘su -’) before proceeding.

I tried this guide,but it show the following message :
device-mapper: remove ioctl failed: Device or resource busy

what should I have to do?