[xubuntu-users] restarting window server or possibly usb service remotely

[Dan Hitt]

Ah Victor thanks a million!

Turning off the monitor turns out to be key.

If i turn off the HDMI monitor, lightdm (or whatever the underlying
service is) seems to take that as a signal to never return.

So that means that there is a work around.  First, do ctrl-alt-f1 to
get into a virtual monitor.  Then turn off the monitor.

And coming back, just do the reverse: turn on the monitor, then do
ctrl-alt-f7 to get back xwindows.

This is possibly related to another problem that i have, where i
cannot listen to headphones plugged into my hdmi monitor.  (Under
ubuntu 15.10 i could do this, so i know it is not a hardware problem.)

Now, unfortunately, i'm far too ignorant to have any ideas about your
question "with modern lcd monitors is there any difference between
sleep and a software shut off?"

But i think it would be useful to know in order to construct some sort
of model of how hdmi works (what states can a monitor be in, and what
transitions are possible under what conditions between the states).

Anyhow, thanks again for your help!  (And thanks everybody else also.
I've learned something from every suggestion.)

dan


On Sun, May 8, 2016 at 11:32 AM, Victor Forberger
<vforberger at fastmail.fm> wrote:
> On 05/08/2016 11:52 AM, Dan Hitt wrote:
>> On Sun, May 8, 2016 at 5:07 AM, Petter Adsen <petter at synth.no> wrote:
>>> On Sat, 7 May 2016 20:32:03 -0700
>>> Dan Hitt <dan.hitt at gmail.com> wrote:
>> .....
>>>> Occasionally after i lock the screen and come back after a few hours i
>>>> cannot get it to respond.
>>>>
>>>> The machine is alive, and i can ssh into from another host.
>>>>
>>>> But wiggling the mouse and pressing keys leaves the monitor pitch
>>>> black.
>> .....
>>>
>>> If you don't mind restarting your entire X session, you can try 'sudo
>>> systemctl restart lightdm.service'. You could also try to kill the
>>> screen locker process, I think Xfce uses light locker by default.
>>>
>>
>> Thanks Petter!
>>
>> So the problem came up again after i last wrote (i had to go do some
>> chores, and when i came back keyboarding and mousing did not bring
>> back the display).
>>
>> So i tried your suggestion of restarting lightdm.
>>
>> And it worked, so thanks!
>>
>> I did lose my X state, but i don't think any other state.
>>
>> This seems to indicate that lightdm is going into too deep a sleep, or
>> perhaps taking something to sleep with it that should stay awake.
>>
>> If anybody has any advice about how to approach this kind of lightdm
>> problem, i'm all ears --- although i know next-to-nothing about
>> lightdm.
>>
>> Thanks again everybody for all the suggestions.  They were all helpful.
>>
>> dan
>>
> I had a similar problem a ways back. I'm sorry if I can't pull up
> specific info from my past problem-solving (I searched through various
> logs in /var/log for log entries that identified what the problem was).
>
> But, I do recall the problem was actually related to the monitor being
> shut off (as opposed to just dimmed). When unlocking the computer for
> use after a long delay, the process for turning the monitor back on was
> not working. I fixed the problem by changing power manager settings so
> that the display was never turned off, only put to sleep. Once that
> setting was changed, lightlocker could activate the monitor again once
> the session was unlocked.
>
> Restarting lightdm certainly will also do the trick. But, it is a
> radical solution, especially if the problem is just related to getting
> the monitor to connect to the xfce window manager (note that xfce runs
> on top of lightdm -- i.e., lightdm provides the login screen when the
> computer is turned on; xfce is the actual desktop environment for
> getting work done after a successful login).
>
> And, one question here: with modern lcd monitors is there any difference
> between sleep and a software shut off?
>
> - Victor
>
> --
> Victor Forberger
> vforberger at fastmail.fm
> blog: http://linuxatty.wordpress.com
>
>
>
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