To maintain session accross xyz.com and www.xyz.com

I have a rails website on www.xyz.com. After I log in to www.xyz.com, if if move to xyz.com, I need to log in aga开发者_如何学编程in, ie the session is not maintained. How to make www.xyz.com and xyz.com use the same session.

I'd recommend sticking with one or the other. It's better for SEO and much easier to deal with.