root@dan-vbox:/var/log/lightdm# cat unity-system-compositor.log 
[1446058204.783922] mirplatform: Found graphics driver: mesa-kms
[1446058204.783968] mirplatform: Found graphics driver: mesa-x11
[1446058204.786629] mirserver: Starting
[1446058204.788688] mircommon: Loading modules from: /usr/lib/x86_64-linux-gnu/mir/server-platform
[1446058204.788752] mircommon: Loading module: /usr/lib/x86_64-linux-gnu/mir/server-platform/graphics-mesa-kms.so.6
[1446058204.788778] mircommon: Loading module: /usr/lib/x86_64-linux-gnu/mir/server-platform/server-mesa-x11.so.6
[1446058204.789497] mirplatform: Found graphics driver: mesa-kms
[1446058204.789520] mirplatform: Found graphics driver: mesa-x11
[1446058204.789557] mirserver: Selected driver: mesa-kms (version 0.17.0)
ERROR: /build/mir-n3hlNX/mir-0.17.0+15.10.20151008.2/src/platforms/mesa/server/common/display_helpers.cpp(256): Throw in function int mir::graphics::mesa::helpers::DRMHelper::open_drm_device(const std::shared_ptr<mir::udev::Context>&)
Dynamic exception type: boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::runtime_error> >
std::exception::what: Error opening DRM device
123, "No medium found"