How do I rotate the login screen?

So I am trying out the 14.04 and I keep both of my monitors in portrait mode. But the login splash is in landscape. But I can't seem to figure out how to rotate my login splash or where the config is for it? It is no longer in /etc/lightdm/lightdm.conf

Can anyone help?

Solution 1:

DBX12's answer is good. Let me add 2 details that I had to figure out in 18.10:

• Instead of [SeatDefaults] current versions expect [Seat:*]
• More importantly: I had to experiment a little with the above script using logger and then xmessage to conclude, that it does get called, it does set things right, but then its effect is unfortunately undone by unity-greeter.

I tried other greeters, and they all honor the solution and start up nicely rotated, except the default unity-greeter. I ended up using slick-greeter.