II've been trying to auto login, Kubuntu 14.10 KDE 5 plasma. I had this working by adding sddm.conf file in the etc dir containing:
[Autologin] User=$USERNAME Session=plasma.desktop
Substitute your user name for
$USERNAME. Well, this "was"working fine. I've been doing regular:
sudo apt-get update sudo apt-get upgrade sudo apt-get dist-upgrade
While keeping an eye on sddm.conf file... It's still there, content unchanged, however, no more auto login!