Adding a username alias using the command line How do I add a username alias using the command line?

I can do it fine using the preferences dialog through the "Advanced Options", but I need to do it during an installation script. 

Can someone point me the right way?
The information is accessible through dscl. To add the alias "visitor" and be able to use this username for guest login, use the following command:

sudo dscl . -merge Users/Guest RecordName visitor