After update my system to 15.04, I have an error message at the boot: 'starting build 219'.
The bug is known, its recommend to go to console mode and enter this command:
sudo systemctl enable sddm.service -f
But when I enter this command I get an error message:
Error getting authority: Error initializing authority: Could not connect: No such file or directory (g-io-error-quark, 1)
You may get such an error if your display manager is not sddm.
Running the following can show which display manager you are using :
For example, if your display manager is /usr/sbin/gdm, running the following may help :