Trick Linux Mint Cinnamon in headless mode to think a monitor is connected?

Question

Here is what I have so far:

• Headless server running Linux Mint with Cinnamon as the desktop
• x11vnc installed
• No monitor is connected to the server

The problem I'm running into is that x11vnc is terribly slow even with a GigE connection between the server above and the client machine.

I noticed that when the monitor was connected to the server via a VGA cable but not powered on(the monitor that is) that x11vnc became dramatically better.

Some digging around led me to the a github issue for x11vnc mentioning that if you turn off compositing in Ubuntu, that can help [0]. I tried turning off "Effects" and setting vsync to None in Cinnamon but no luck.

I then dug into /var/log/syslog and noticed that xrandr detected the monitor when I connected the VGA cable (again even though it was unpowered). This also dramatically improved the vnc performance.

Is there some way to trick Linux Mint into thinking that monitor is there?

[0] - https://github.com/LibVNC/x11vnc/issues/102

Answer 1

The accepted answer, which recommends a dummy HDMI plug, would give users several choices of video resolution. I may do that, since the default resolution of 800x600 is a bit chunky, and does not allow for a lot of working space.

However this post gives a good-enough solution to the speed problem. Simply add the string nomodeset to this Grub variable in /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"

Then just run update-grub as root and reboot. I now have sub-second VNC redraw times over my LAN!

Answer 2

I just set up a headless build running Mint Cinnamon and hit the same problem. VNC is lightning fast with a monitor attached, but once you remove it and reboot it moves slower than molasses.

This is definitely a workaround but you can purchase dummy HDMI plug online for a few bucks. They come in a variety of common resolutions and trick the device into thinking a display is attached.

This isn't the most elegant solution but it's definitely the least painful one for me.

Answer 3

I have never done this myself but xorg offers a dummy video driver and there is also the xdummy package for Ubuntu that helps get this up and running here is the link to the package. http://manpages.ubuntu.com/manpages/focal/man8/Xdummy.8.html