I have no idea how to start debugging this. My laptop is a Dell XPS 13, model 9333. The behaviour started when I upgraded to 15.04 (from 14.10), and to Gnome 3.16 (from 3.14). Unfortunately I'm not sure which upgrade caused it, because I did them both at the same time.
What happens is pretty straight forward. I hit shutdown, the shutdown process does its thing until the screen goes blank, but the laptop remains powered on (the little light at the front of the laptop, and the keyboard backlight, stay powered on).
When this happens my laptop does disconnect from Wi-Fi. Nothing appears to happen when I try to switch to other TTY (ctrl alt F1,2,3,4...) - perhaps something is happening and I'm not seeing it because the screen is off, I don't know. The machine DOES appear to disable it's wi-fi when I use the fn+wifi toggle button (because on my next boot the laptop is in "airplane mode").
The only way to power my laptop down when this happens is to hold the power button. After powering down like this I have sometimes (not always) had the next boot run a filesystem check and then dump me into an emergency console, where reviewing the logs in
journalctl -xb tell me I need to run
sda9 before I can boot - so I do that
e2fsck /dev/sda9 -y and then reboot, and everything works fine.
Does anybody have any ideas how to start debugging this issue? Are there any logs I can check, and anything in particular to look for to identify why the laptop is not powering off?
Any help would be greatly appreciated.
(edit) Looks like this must be a gnome 3.16 problem. Shutting down after logging into Unity works fine, but shutting down from the Gnome lock screen or from logging in to Gnome consistently fails. Any idea how to debug this further?
(edit 2) More info. Running
sudo shutdown -h now fails when ran via a terminal window in Gnome. Running
sudo shutdown -h now via tty1 (when logged in to gnome or when the gnome lock screen is open, on tty7 (i think)) results in a successful shutdown. Running
sudo shutdown -h now via unity results in a successful shutdown. The problem is clearly confined to Gnome 3.16 then. :\