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My engineering team has four special shared computers running a mix of Ubuntu Desktop 16.04 and 18.04 that are in a lab that's a 5-minute walk from our cubes. We need remote desktop access for these machines (we have graphical test tools that can't be run in a SSH session, for example), and we want to be able to use separate user accounts on these systems so we can have separate shares/user directories, etc.

I've tried both Vino and x11vnc. Both of these solutions work fine for a single Ubuntu user account only, but the moment a logged-in VNC user tries to switch to their personal Ubuntu account (when the Ubuntu user selection screen appears), the VNC screen goes black and no keyboard/mouse controls have any effect on the remote system. If I go up to the lab and manually switch back to the original user account on the physical PC, then the VNC session becomes usable again.

Things I have tried:

• Tried Ubuntu 16 vs 18, and x11vnc vs. Vino. Results the same across the board- the moment the connected user tries to switch accounts (vs. logging off, etc), the moment the user selection screen appears on the physical desktop, the VNC client screen goes blank and unusable.


• 
  Followed these instructions to configure x11vnc to start at boot (unlike the default Vino setup which only starts after a user with Vino configured logs on). I can log into any ubuntu user account over VNC when I do this, but once I'm logged in, any attempt to switch to another ubuntu account results in the black screen problem for the VNC client. So basically VNC is good for a single user-specific session and then it requires either manual intervention in the lab or a reboot to reset X11vnc to a usable state.


• Configured Vino to use unique ports for each user instance, then manually logged in to all local user accounts (starting their Vino server instances). This was interesting because only one VNC session was usable at a time (only one could interact with the computer, others either had a black or frozen screen). But the moment I tried to switch accounts, again, all VNC clients became unusable. If I manually switched to one of the other logged in accounts, that user's VNC session would become interactive/usable.

My questions:

• Is it possible to change this behavior where the user selection screen breaks VNC clients?


• Is there a different Ubuntu 16/18-compatible remote desktop client that would allow graphical remote desktop in a multi-user environment? (I think TeamCity might work, however that's unfortunately a banned tool in our environment.)

Thanks!

I had the same problem with Ubuntu 18.04 and x11vnc. I solved it by using lightdm instead of gdm3. Make sure to configure your x11vnc service accordingly.

Likely due GUI session controls locks, I had update .vnc/xstartup to unset session variables before starting a window manager, and that did the trick to get multiple user sessions working on 18.04.

unset SESSION_MANAGER
unset DBUS_SESSION_BUS_ADDRESS

Follow more helpful/complete instruction at
https://wiki.archlinux.org/index.php/TigerVNC#Running_vncserver_for_virtual_(headless)_sessions