New answers tagged gdm
I had the same problem on Ubuntu 14. I used Ctrl+Alt+f2, then logged in. When I inspected the file "/etc/profile", I found that I had inserted an illegal character while setting up the path. After correcting that, I logged off and restarted and my GDM was working perfectly. I would advise you to inspect the file for illegal characters.
I'm not sure exactly what I did to get lightdm to successfully start a session for me except maybe allowing anyone (not just consoles) to connect to the xserver. The gnome-shell desktop still doesn't appear when I login through lightdm while it does when using startx.
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