[CentOS] How to create user with period (.)

hi guys,
 how can i create a username with period ? Like for example
 username: linux.spartacus 
 
 tia
 
		
---------------------------------
Relax. Yahoo! Mail virus scanning helps detect nasty viruses!
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.centos.org/pipermail/centos/attachments/20060301/21bda2b6/attachment.html>