Screen Blanking not working for XFCE / LightDM

[cytek-jy]

I am unable to get screen blanking to work. I am using Ubuntu that I set up with XFCE and LightDM with Nouveau drivers for an Nvidia GPU.

I am using the free NoMachine product. Is screen blanking supported with this product?

If it is supported are there any recommended debug steps? I have tried looking in the server logs, reinstalling nomachine, toggling the screen blanking setting, restarting the server, I have tried disabling compositing on XFCE as well. No luck with any of these.

Thanks – Jack

[cytek-jy]

I also tried to enable screen blanking on a fresh standard installation of Ubuntu 24.04 LTS and it also did not work, so I don’t think the problem is unique to XFCE / LightDM. This 24.04 LTS is using Gnome and Wayland.

[Britgirl]

Screen blanking is supported in all products. We are not aware of screen blanking issues when connecting to a physical desktop on XFCE. Does it also not blank screen from the !M icon of the system tray? (Desktop shared > Blank physical screen). Can you send the us the logs of the server host? Reproduce the issue again, then on the server host, go to the Server settings > Security > scroll down and click Take logs). You can attach them here or if you prefer send direct to forum[at]nomachine[dot]com. Thanks.

[cytek-jy]

I have verified that the in !M tray item’s menus “Blank physical screen” is checked.

I was unable to upload the logs here so I have sent them in an email.

Given that I was able to replicate this on a fresh install of ubuntu (from ubuntu-24.04.3-desktop-amd64.iso) it may be that this problem is not specific to XFCE/LightDM.

Is there any other information I can provide? Thanks.

[Britgirl]

Can you open a terminal and run the ‘xrandr --verbose‘ command on the XFCE host? Please send us this output.

Can you also send us the logs where reproduce the same issue on Ubuntu 24.04 and Wayland? That way we can compare. Send them to forum@ email address like last time. Thanks!

[cytek-jy]

Here is the output on the XFCE machine.

$ xrandr --verbose
Screen 0: minimum 320 x 200, current 3840 x 2160, maximum 4096 x 4096
None-1 connected 3840x2160+0+0 (0x41) normal (normal left inverted right x axis y axis) 0mm x 0mm
Identifier: 0x3f
Timestamp: 30411
Subpixel: unknown
Gamma: -9.2e-09:-9.2e-09:-9.2e-09
Brightness: 0.23
Clones:
CRTC: 0
CRTCs: 0
Transform: 1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000
filter:
link-status: Good
supported: Good, Bad
CONNECTOR_ID: 37
supported: 37
non-desktop: 0
range: (0, 1)
3840x2160 (0x41) 497.664MHz *current +preferred
h: width 3840 start 3840 end 3840 total 3840 skew 0 clock 129.60KHz
v: height 2160 start 2160 end 2160 total 2160 clock 60.00Hz

I will share logs from the Ubuntu 24.04 wayland sessions tomorrow. Thanks!

[Britgirl]

Hi, we’ll wait for your logs. In the meantime, can you tell us if the xrandr --verbose output was captured with screenblanking enabled and during an active connection? If it was, please also submit xrandr --verbose when blanking is disabled (or when nomachine is not connected). Sorry for not specifying this earlier.

[cytek-jy]

I’ve sent the Ubuntu Wayland logs.

I believe that XFCE xrandr output was taken on an active session with screen blanking enabled.

To be sure I reran while disconnected and got this:

$ xrandr --verbose 
Screen 0: minimum 320 x 200, current 3840 x 2160, maximum 4096 x 4096
None-1 connected 3840x2160+0+0 (0x41) normal (normal left inverted right x axis y axis) 0mm x 0mm
	Identifier: 0x3f
	Timestamp:  30411
	Subpixel:   unknown
	Gamma:      1.0:1.0:1.0
	Brightness: 1.0
	Clones:    
	CRTC:       0
	CRTCs:      0
	Transform:  1.000000 0.000000 0.000000
	            0.000000 1.000000 0.000000
	            0.000000 0.000000 1.000000
	           filter: 
	link-status: Good 
		supported: Good, Bad
	CONNECTOR_ID: 37 
		supported: 37
	non-desktop: 0 
		range: (0, 1)
  3840x2160 (0x41) 497.664MHz *current +preferred
        h: width  3840 start 3840 end 3840 total 3840 skew    0 clock 129.60KHz
        v: height 2160 start 2160 end 2160 total 2160           clock  60.00Hz

And reran while connected with nomachine with screen blanking enabled and got this:

$ xrandr --verbose 
Screen 0: minimum 320 x 200, current 3840 x 2160, maximum 4096 x 4096
None-1 connected 3840x2160+0+0 (0x41) normal (normal left inverted right x axis y axis) 0mm x 0mm
	Identifier: 0x3f
	Timestamp:  30411
	Subpixel:   unknown
	Gamma:      8.3e-08:8.3e-08:8.3e-08
	Brightness: 0.25
	Clones:    
	CRTC:       0
	CRTCs:      0
	Transform:  1.000000 0.000000 0.000000
	            0.000000 1.000000 0.000000
	            0.000000 0.000000 1.000000
	           filter: 
	link-status: Good 
		supported: Good, Bad
	CONNECTOR_ID: 37 
		supported: 37
	non-desktop: 0 
		range: (0, 1)
  3840x2160 (0x41) 497.664MHz *current +preferred
        h: width  3840 start 3840 end 3840 total 3840 skew    0 clock 129.60KHz
        v: height 2160 start 2160 end 2160 total 2160           clock  60.00Hz

Hope this helps.

[Britgirl]

The logs don’t reveal any errors. Can you tell us details of:

– graphics card
– driver version
– monitor model

for both the computers running Xfce and Gnome/Wayland?

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