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I am running "Ubuntu 16.04.4 LTS" on a desktop. Sometimes after running for a while the screen goes black and I can no longer access the computer locally. This includes alt-F1 etc.to get to a terminal screen. Without the screen I can't tell if mouse or keyboard input is being processed.

I can however log in remotely and see that some other things (e.g. web servers) are apparently running as normal.

What can I do to diagnose the problem? Is there some command I can execute from my remote login (I have root of course) to get the 'screen driver' to 'restart'?

I'm not even sure how to tell which display manager process should be running. A few years back I could recover a crashed wm using something like metacity --replace or compiz --replace. I'm not so sure now.

I am using "gnome classic" (I think).

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2 Answers 2

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Start by seeing which display manager you're using: 

service --status-all |& grep -E 'gdm|lightdm'

On my Ubuntu 16.04.4 LTS, it happens to be lightdm, YMMV.

Follow this with

service lightdm status

and other diagnostic techniques, then,

sudo service lightdm restart

See This link on Ask Ubuntu - one of its many answers may help you.

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  • Its neither in my case. That would restart the display manager not the window manager. I could identify the window manager using wmctl -m but all I got was "can't open display".
    – Bruce Adams
    Jun 7, 2018 at 3:12
  • It would by systemctl restart lightdm under systemd.
    – Bruce Adams
    Jun 11, 2018 at 8:23
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Not quite at an answer yet. In my case the display manager seems to be sddm. At least:

systemctl sddm restart

gets the display to reappear. I still lose my windows though. I confirmed with wmctrl -m that my window manager is gnome-shell. Next time it happens I'll try gnome-shell --replace &.

The cause is still unknown to me. https://unix.stackexchange.com/questions/447999/identify-and-restart-gnome-classic-window-manager-on-rhel7

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