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Thread: No screen without monitor plugged in (VNC, TeamViewer)

  1. #1

    Default No screen without monitor plugged in (VNC, TeamViewer)

    Hello,

    I have a specific problem I am unable to solve on my own, so I ask for your help. I have LEAP 42.1 installed on a DELL PC with Intel integrated GPU. Installation was fine but when I was preparing my PC I found out one big issue. I need to access my PC remotely via VNC, occasionally with TeamViewer.. It works great as long as I have a monitor plugged in. At the very moment I unplug it, my VNC or TW screen goes black and that's it. When I plug the monitor back in, the screen will reappear.

    Using KDE with Plasma 5.
    Integrated GPU.
    Using X11VNC.

    Another problem that goes with this is when I boot the PC without monitor plugged. The PC goes up, and when I plug the monitor cable into the PC, I still have no screen. The monitor won't receive signal from PC. I have to restart the computer and then it works.

    I don't have any of these problems on Windows. Only here on SUSE 42.1. Anybody got ideas how to set this up ? That means if I start the PC without monitor attached, the screen will go up as usual ? And when I unplug the monitor from a running PC the remote screen won't go black ?

    Thank you very much

  2. #2
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    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    Quote Originally Posted by CruiserCZ View Post
    Using X11VNC.
    Per their website, X11VNC allows VNC connections to real X11 displays and that's the problem. You can't use a real X11 display because it doesn't exist without a real login session with a monitor etc. What you want is more like a virtual session. I would suggest looking into tightvncserver. This will create new a session that are not tied to a real session and can be used with a headless configuration. XRDP may also be an option but it can be a pain in the rear to set up.
    Do what you can, with with you have, where you are.
    --Theodore Rooselvelt

  3. #3
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    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    It's almost certain that you did not install VNC using YAST > Remote Administration.

    When you use the YAST tool, it installs xserver which provides among other things headless support (ie no monitor connected).

    The openSUSE community docs are pretty good on this subject, including how to configure different VNC session configurations.
    https://doc.opensuse.org/documentati...e/cha.vnc.html

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  4. #4

    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    SDDM (which is used by default on a KDE installation) doesn't support VNC though, so Remote Administration in YaST won't work, i.e. you won't be able to connect to the host via VNC (unless you run x11vnc in a running session).
    And also SDDM doesn't show a login screen without a display connected, see https://github.com/sddm/sddm/issues/598.

    I would therefore suggest to switch to a different displaymanager/login screen if you want to use VNC or boot without a display connected, e.g. lightdm or kdm.
    Install it and set DISPLAYMANAGER="xxx" in /etc/sysconfig/displaymanager accordingly.

  5. #5
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    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    Quote Originally Posted by wolfi323 View Post
    SDDM (which is used by default on a KDE installation) doesn't support VNC though, so Remote Administration in YaST won't work, i.e. you won't be able to connect to the host via VNC (unless you run x11vnc in a running session).
    And also SDDM doesn't show a login screen without a display connected, see https://github.com/sddm/sddm/issues/598.

    I would therefore suggest to switch to a different displaymanager/login screen if you want to use VNC or boot without a display connected, e.g. lightdm or kdm.
    Install it and set DISPLAYMANAGER="xxx" in /etc/sysconfig/displaymanager accordingly.
    That's a few things now that I know do not work with SDDM. I am meaning no criticism here, just asking if you know why SDDM was chosen for LEAP with these problems? This is a genuine "I would like to know ..." question, nothing else.
    -Gerry Makaro
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    Solving Tech Mysteries since the Olden Days!
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  6. #6

    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    Quote Originally Posted by Fraser_Bell View Post
    That's a few things now that I know do not work with SDDM. I am meaning no criticism here, just asking if you know why SDDM was chosen for LEAP with these problems? This is a genuine "I would like to know ..." question, nothing else.
    Mainly because it was chosen by the upstream KDE developers as recommended display manager for Plasma5 when they decided to drop KDM (lightdm was the other option, but they thought they might have more influence on SDDM's development IIRC).
    Therefore it is also the only one that has some "official" integration with Plasma5, e.g. KDE provides a theme for it based on the default Plasma theme and a config module in systemsettings5.

    And it is Qt5 based.

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    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    Quote Originally Posted by wolfi323 View Post
    Mainly because it was chosen by the upstream KDE developers as recommended display manager for Plasma5 when they decided to drop KDM (lightdm was the other option, but they thought they might have more influence on SDDM's development IIRC).
    Therefore it is also the only one that has some "official" integration with Plasma5, e.g. KDE provides a theme for it based on the default Plasma theme and a config module in systemsettings5.

    And it is Qt5 based.
    Thank you, I appreciate the information and will file it away for future knowledge.
    -Gerry Makaro
    Fraser-Bell Info Tech
    Solving Tech Mysteries since the Olden Days!
    ~~
    If I helped you, consider clicking the Star at the bottom left of my post.

  8. #8

    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    Okay I tried to use LightDM but it won't let me log in. When I enter the password the login screen just refreshes itself but nothing happens. Also VNC is not working. Am I supposed to configure lightdm somehow ?

  9. #9
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    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    Quote Originally Posted by CruiserCZ View Post
    Okay I tried to use LightDM but it won't let me log in. When I enter the password the login screen just refreshes itself but nothing happens. Also VNC is not working. Am I supposed to configure lightdm somehow ?
    No configuration is possible AFAIK,
    But I've noticed what you're describing with my recent experimentation with other DM (Yours is the first time I've heard that Lightdm caused this problem).

    The only way I've found to fix your problem is to boot to a LiveCD and modify the DM setting manually.

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  10. #10

    Default Re: No screen without monitor plugged in (VNC, TeamViewer)

    Quote Originally Posted by CruiserCZ View Post
    Okay I tried to use LightDM but it won't let me log in. When I enter the password the login screen just refreshes itself but nothing happens.
    Strange.
    Does it work if you choose a different desktop session at the login screen?

    Also VNC is not working. Am I supposed to configure lightdm somehow ?
    Did you enable "Remote Administration" in YaST?
    Is the vnc service active in YaST->Network->Network Services (Xinetd)?
    Is the corresponding port open in the firewall? Try to disable the firewall completely as a test.

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