unity8 black screen

Attaching more logs

Any chance you're seeing bug #1525285 ? Please run an X11 session once (to get the gst registry regenerated) and then log in to unity8 again.

Thank you for letting me know. I am aware of bug #1525285 and I tried to run gst-inspect-1.0 in my old unity7/Xorg session. The command ran successfully and produced a lot of output; yet the Mir session still won't start.

Oh, finally resolved this: while starring at the blank screen, waiting for unity8 to start, I pressed CTRL+ALT+F8 and voila - the screen suddenly shown the unity8 :-) Thank you.

Sorry, back to "can't run unity8": after the computer boots up, no matter how much I press CTRL+ALT+F1-F12, nothing happens, the screen stays completely blank.

unity8.log.2.gz from comment #2 shows Unity8 is crashing. Seemingly because something in the Unity8 process is pulling in the old (non-lite) libprotobuf.so.9 that conflicts with Mir's libprotobuf-lite.so.9:

[2016-03-23 22:25:19.703080] <ERROR> MirSurfaceAPI: Caught exception at client l
ibrary boundary (in mir_surface_release): /build/mir-ZgPdOQ/mir-0.20.2+16.04.201
60307/src/client/rpc/stream_socket_transport.cpp(168): Throw in function virtual
 void mir::client::rpc::StreamSocketTransport::send_message(const std::vector<un
signed char>&, const std::vector<mir::Fd>&)
Dynamic exception type: boost::exception_detail::clone_impl<boost::exception_det
ail::error_info_injector<mir::socket_disconnected_error> >
std::exception::what: Failed to send message to server: Broken pipe
32, "Broken pipe"
*** Error in `unity8': free(): invalid pointer: 0x00007f9eb00e6ef0 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x778bf)[0x7f9edfd118bf]
/lib/x86_64-linux-gnu/libc.so.6(+0x8010a)[0x7f9edfd1a10a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f9edfd1dc5c]
/usr/lib/x86_64-linux-gnu/libprotobuf.so.9(_ZN6google8protobuf8internal28DestroyDefaultRepeatedFieldsEv+0x71)[0x7f9ea311f901]
/usr/lib/x86_64-linux-gnu/libprotobuf-lite.so.9(_ZN6google8protobuf23ShutdownProtobufLibraryEv+0x8b)[0x7f9ed638472b]
/usr/lib/x86_64-linux-gnu/libmirprotobuf.so.3(+0x20359)[0x7f9ed6bde359]
/lib64/ld-linux-x86-64.so.2(+0x10bb7)[0x7f9ee21d0bb7]
/lib/x86_64-linux-gnu/libc.so.6(+0x3a088)[0x7f9edfcd4088]
/lib/x86_64-linux-gnu/libc.so.6(+0x3a0d5)[0x7f9edfcd40d5]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf8)[0x7f9edfcba848]
unity8(_start+0x29)[0x406a29]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1535297, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.