So typically I would not recommend auto login setting be set for your system but there are some exceptions. For example, when that system is a Virtual Machine running on your desktop.
I've been playing around a lot with my Ubuntu configuration on a virtual machine running under VMWare Fusion. I got tired of having to log into the machine every time I booted it when I was already logged onto my desktop of the host machine. So for the first time, I found myself trying to figure out how to auto login my Linux desktop. In my typical “learn the hard way” fashion, I over thought the problem and approach several times before discovering how simple it was. A couple of clicks to be exact.
Step 1: Fire up a terminal screen and type “ sudo gdmsetup ”
Step 2: This should bring up the “Login Window Preferences” dialog box. Click on the security tab, click the check box for “Enable Automatic Login”, select the user you want to Auto Login as and click close.
That's it, couldn't be simpler.