If you’re on ubuntu 14.04, you’re mostly on kernel 3.13.x. Maybe even 3.14.x. But, the problem with these is, you can not have a setup like this :
What I mean is, you can not have two monitors connected and all three screens working in harmony, in extended mode. This problem is called a DP MST Problem. DisplayPort Multi-Stream (DP MST) isn’t working, because it does not exist in that kernel version. For the record, I am using a Dell Latitude E7250, and have connected it to a DockStation or Dell E-port, whatever you wanna call it. One external monitor is connected using DVI cable, and other using VGA. You would think this should work, but it doesn’t. Both the external monitors get recognized as just one monitor and they mirror/duplicate each other.
So, to solve this problem, there are two approaches here –
- Upgrade to ubuntu 15.04 or higher (have out of the box support for DP MST)
- Upgrade your kernel and intel drivers (I’m assuming you’re having a simple machine having integrated drivers. If you have a graphic card, you MIGHT need to install its drivers too.)
I did not want to update my ubuntu because of LTS version, and knowing that most of my peers are also on 14.04, it was a better choice right now. So, I went ahead with the second method.