I am facing the same issue. I have upgraded from Xubuntu 14.04 to Xubuntu 16.04 and I was greeted with a black screen just after my first reboot.
I use a Radeon HD 5430 card with two monitors. Incidentally, I had to switch off one of them so that the Live USB from which I installed the upgrade would work. The problem, though, started with the reboot. This is the output of my uname -a: Linux tiramisu 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux There are three ways in which I can "start" my computer: * Normal boot, which ends in a black screen. * Recovery mode, which, after selecting "continue boot", generates errors such as "*ERROR* no UMS support in radeon module!" above, defaults to VESA module (and poor resolution), and cannot manage two screens. I enclose the Xorg.1.log file for this method. * Recovery method and deleting the nomodesetting kernel option. After selecting "continue boot", I get a perfectly working environment: radeon module works, etc. I enclose the Xorg.0.log file for this method. ** Attachment added: "Corresponds to a "clean" boot" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1568211/+attachment/4645367/+files/Xorg.0.log -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1568211 Title: no UMS support in radeon module To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1568211/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
