I do not believe that Ubuntu packages a FCoE target. So, what you're doing with the above commands is trying the 'create' or start FCoE, as an initiator, on eth2. The fcoe-utils package, at least upstream (i.e. on Open-FCoE.org), does not support a target mode.
So, you're barking up the wrong tree, but how do you get a working FCoE target?
The biggest problem with answering this question is that there are multiple FCoE targets floating around of varying age (i.e. bit rot) and stability. The most current and well tested FCoE target, to my knowledge, is the TCM based FCoE target that was recently posted upstream. See this patch: http://open-fcoe.org/patchwork/patch/1859/. It has not been accepted yet, but it is targeted for the 2.6.40 merge window. Aside from this patch to enable kernel support the fcoe-utils suite will need code changes for fcoeadm/fcoemon to support target mode. There are currently a few outstanding issues regarding the user's selection of running in initiator or target mode and I'm not aware of any existing code for fcoe-utils and target mode.
On top of that upstream work these changes will need to make their way into distros, Ubuntu in this case.
So, I guess I don't have a great answer for you other than to say FCoE target is coming soon, but until then you'll probably need to do some source level patching. Check the email@example.com mailing list archives as you can probably find other threads about how to get a FCoE target working from source.
One other thing to point out is that configuring the TCM based FCoE target requires you to use the lio-utils package to get the TCM managemt applications.
I hope this helps, //Rob