I spent a couple of evenings on this, and it's getting a bit frustrating since I managed to had it working on my previous Ubuntu (MANY years ago).

I'd like to have an vnc server running on my server at any time (including login screen) to remotely connect and login. Not a different session: share the same session I would see on the physical display of my server and log on to it remotely via VNC in a private network (aka home).

I understand it's a combination of XDMCP, GDM3, initd and VNC configurations, but I don't have enough experience to tune the various howtos I found online to work for ubuntu 18.04.

These seems promising links: https://lists.debian.org/debian-user/2017/04/msg00529.html https://codeghar.wordpress.com/2009/06/11/remote-login-with-gdm-and-vnc-on-fedora-11/ https://wiki.openindiana.org/oi/4.7+Remote+Graphical+Login:+Using+Xvnc+and+gdm+for+One-Shot+sessions

Right now (in case anyone else is going crazy like me), I installed nomachine and it took the grand total of 2 minutes to setup and it works as I wanted (including iOS clients!): https://www.nomachine.com/ ---bittersweet ¯_(ツ)_/¯

  • Need to bind x11vnc to screen instead of session. – Seb Jun 6 '18 at 8:51
  • 2
    Thank you for the NoMachine rec. After a weekend of installing x11vnc, tightvnc, tigervnc, vnc4server and more and nothing working with 18.04 and gdm3, I finally gave up and used NoMachine, worked perfectly. Pretty disappointed in 18.04 LTS right now though. – jb510 Aug 12 '18 at 18:09
  • I went the same path: frustrating evenings trying to get various vnc solutions working but to no avail. Installed nomachine and it works (though not in 2 minutes due to: nomachine.com/AR03P00973). Anyway: now that I see the solution below (switching to lightdm), I wonder: did you try it? Is it worth switching from nomachine to this more open source solution? – Christoph Feb 3 '19 at 23:30
  • I tested @seb solution with Debian 10 with Mate and it worked. – S.V. Aug 23 at 2:08

Ubuntu 18.04 switched from LightDM to GDM3. Connecting to the login screen with VNC while using GDM3 is currently not possible. The easiest way to get this VNC functionality back is to simply switch back from GDM3 to LightDM.

LightDM is still being actively developed and used by many Linux distributions including some other flavors of Ubuntu. So no worries there.

Install LightDM

apt install lightdm

Should you for some reason come to regret switching to LightDM:

dpkg-reconfigure gdm3

Once you have LightDM installed and configured as your default greeter..

Install x11vnc from packages

apt install x11vnc

Create the file /etc/systemd/system/x11vnc.service

# Description: Custom Service Unit file
# File: /etc/systemd/system/x11vnc.service

ExecStart=/usr/bin/x11vnc -loop -nopw -xkb -repeat -noxrecord -noxfixes -noxdamage -forever -rfbport 5900 -display :0 -auth guess
ExecStop=/usr/bin/killall x11vnc


Enable the x11vnc service

 systemctl enable x11vnc.service

This assumes screen :0 represents your monitor and binds x11vnc to that monitor instead of a session. If you do not have a monitor (headless) I believe it is possible to install a fake monitor driver and bind x11vnc to that.

Side notes

  1. Incase you are using virt-manager (which also enables VNC on you may want to bind x11vnc to your LAN IP (-listen
  2. The parameters used to start x11vnc tell it not to ask for an additional password (-nopw)
| improve this answer | |
  • 1
    To start vnc session x11vnc -display :0 It can only connect to one session, once your session is expired or closed, you will have to start again with x11vnc -display :0 – ashish Aug 30 '18 at 5:58
  • "Restart-sec" should be "RestartSec" – eakst7 Dec 31 '18 at 13:15
  • 1
    When you say "fake monitor" for headless, do you mean xserver-xorg-video-dummy? – Christoph Feb 3 '19 at 23:34
  • As a note: never create your own config files in /lib, use /etc: /etc/systemd/system – Lapshin Dmitry Mar 13 at 11:40
  • Modified to include suggested changes from comments. – Seb Apr 23 at 14:48

I have not yet found a nicer way, but if you really want to login it looks like it is possible.

GDM starts one Xsession for the login screen owned by the root user. As far as I can tell it will perform logins approximately this way:

Login, find existing session and switch vt to it or find a new vt and run an Xorg/gnome-session for it.

The first has display :0 and its authority file (gdm user id 121) /run/user/121/gdm/Xauthority. So you can first run a x11vnc (root rights) if you are not logged in for the DM itself and login (your x11vnc will turn black due to the vt switch). You can either start a new x11vnc manually for your new display :1 (no root rights) or start one automatically with your session as any other logon script.

~$ ps -a | grep Xorg
1471 /usr/lib/xorg/Xorg vt1 -displayfd 3 -auth /run/user/121/gdm/Xauthority -background none -noreset -keeptty -verbose 3
5337 /usr/lib/xorg/Xorg vt3 -displayfd 3 -auth /run/user/1000/gdm/Xauthority -background none -noreset -keeptty -verbose 3
/1000/gdm/Xauthority -background none -noreset -keeptty -verbose 

This has been decided at some point (other DMs might do the same in the future)

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Another way of making this work on 100% headless setup (system running inside container and doesn't have any GPU at all) is "On demand multi-user mode" part of TigerVNC article in ArchWiki.

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After testing many many solutions/scripts for vnc, this xtartup file works well for me on ubuntu 18.04 Lts with tiger vnc :

[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
vncconfig -iconic &
dbus-launch --exit-with-session gnome-session &

And this launch command :

vncserver -localhost no -geometry 1024x768 -depth 24

Taken from this tutorial :

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I am on Ubuntu Server 18.04.4, with ubuntu-desktop installed from tasksel, so i don't really know if this will work with regular out-of-the-box Ubuntu Desktop or if this is a 'going-to-be-obsolete' option.

After trying some 3rd party VNC servers, i ended up with the built in vino-server (Screen Sharing). To run it you need to do~$ /usr/lib/vino/vino-server which then will listen on port 5900, and as this is not enabled by default on/as system service, you may want to create your own systemd entry for enabling it every start-up

Some of the settings can be configured through Settings >> Sharing >> Screen Sharing the rest is through ~$ gsettings set org.gnome.Vino ANY_EXISTING_KEY NEW_VALUE

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  • For any readers that stumbled upon this comment : the weird thing is, there's no (as far as i can search, up until this comment is posted) any recent documentation regarding /usr/lib/vino/vino-server for current(~18.04) or recently-previous Ubuntu versions – Tommy Aria Pradana Jul 17 at 21:58

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