I am running a Natty Beta 2 LiveCD and I realized that by default I booted right into one of the Unity desktop environments. I then looked into the additional drivers app to find that I am not running the usual ATI proprietary graphics driver ubuntu needs to run at full capacity. Based on that I would assume that I am running 2d but I don't know, how do I find that out for myself?
Unity 2D is not a default in 11.04 - it will be in 11.10. Until then, the 11.04 live CD will come with two choices - Unity 3D or Gnome 2. If you see the "launcher-bar" on the left hand side of the screen, you are running Unity using the open-source ATI driver.
You can switch between the two types by logging out and choosing the "Session" type at the bottom of the screen.
If you wish to try Unity 2D look here.
I just run this command in a terminal window:
I see "unity-2d-launcher" in the list of running processes.
Not sure how you'd tell what you're running at a given moment. The login screen allows you to select which environment to use for a session.
If you just want to know if the unity 2D package is installed, you could try this at a terminal:
If the packages listed have a "i" on the far left next to them, that means Unity 2D is installed. If instead there is a "p" or "c", then it's not and therefore you are using the full Unity.