I sometimes experiment with many different desktop environments, some of which can be unstable. I have had a few times where I needed to drop into root shell, disable auto login, then log into my regular desktop, and re-enable the auto-login again.
If I run a desktop from LightDM and it crashes in general, or on logout, Auto login logs me into the last used desktop environment. In trying out questions I want to load a different environment for only one session.
Does LightDM have an option for "This session only" on desktop environments, If not does another login manager have that functionality?
Update: I tried looking into setting up a default login, as explained in this question, How do I change the default session for when using auto-logins? to try and setup a persistent default login,
but as stated here, http://www.tuxgarage.com/2011/09/setting-lightdm-to-auto-login-oneiric.html , "LightDM takes into account the last chosen session, and, thus, overrides any other settings for both 'user-session' and 'autologin-session', set up in the '/etc/lightdm/lightdm.conf'; just make sure your system is updated!" So no go, as it will still login into the last chosen session.
Also from that link I tried setting up an "autologin-user-timeout" hoping that I could do a keypress if there is a delay in the autologin, but this option does not work for reasons stated on the link.