When this happens you should actually be able to press Esc to recover the greeter. You can also press Ctrl+Alt+F1 and log in there, following by "sudo service lightdm restart", that will restart the display manager.
That said, can you please clear /var/log/lightdm and ~/.cache/upstart/, try logging in to the unity8 session and collect the logs from both directories and attach here? ** Changed in: unity8 (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to unity8 in Ubuntu. https://bugs.launchpad.net/bugs/1549455 Title: Unity 8/Mir doesn't load Status in Mir: New Status in unity8 package in Ubuntu: Incomplete Bug description: This bug Makes the pc UNUSABLE when I try to launch Unity 8 and Mir, after writing the password on the login (in the image attached) the bar to enter the password disappears and my computer screen stays stuck without them let me do anything. the connection begins to separate and reattach alone and I can only move the cursor. it makes the computer unusable and I am forced to restart forced to then enter into Unity 7. represented in the screenshot is the lock status after entering the password. Version: unity8.11+16.04.201602.16.1 Version of Mir : 0.20 To manage notifications about this bug go to: https://bugs.launchpad.net/mir/+bug/1549455/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp