How to assign user name and password in Live CD create by Relinux

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http://askubuntu.com – I am preparing a live cd for Koha Open Source Library managment system. I installed Ubuntu 12.04 and login name is koha and password is koha123. My plan is to make live cd with the help of Relinux. Can Relinux can retain the user name and password I created in final Live CD. Same like Remastersys bakcup mode. But I dont want to save other files in Live CD. I expect a wise advise on this matter (HowTos)