[SOLVED] Docker VNC grey screen (only with ubuntu 22.04 image)

General
1

Im running Docker container built on ubuntu 20.04 image.
Image is configured to run XFCE desktop + (tiger)VNC server.

That works fine. However, if I try to build such image with ubuntu 22.04 image, im getting gray screen after connecting via VNC to docker container.

Im running on (other) physical host xubuntu 22.04 with tigetvnc server and there is no such issue.
Anybody knows why it is happening or what is wrong?

Screenshot_2024-02-29_14-36-03
Screenshot_2024-02-29_14-36-03764×623 12.3 KB

Here is my Dockerfile:

FROM ubuntu:20.04

# prevent interactive prompts
ENV DEBIAN_FRONTEND=noninteractive

# update dependencies
RUN apt update
RUN apt upgrade -y

# install xfce desktop
RUN apt install -y xfce4 xfce4-goodies

# install tigervncserver
RUN apt-get install -y tigervnc-standalone-server tigervnc-xorg-extension tigervnc-viewer
RUN touch ~/.Xauthority

Configuration of xstartup:
root@05170e03ea23:/# cat /root/.vnc/xstartup

#!/bin/sh 
xrdb /root/.Xresources 
xsetroot -solid grey 
export XKL_XMODMAP_DISABLE=1 
/etc/X11/Xsession 
startxfce4 &

To start vncserver:

vncserver -depth 16 -geometry 1024x768 -localhost no

2

Here is the Work Around / root cause.

Apparently docker container based on ubuntu:22.04 (in order to start VNC server) must be started with following flag:
--security-opt seccomp=unconfined

Eg:
docker run --rm -ti -d --security-opt seccomp=unconfined --device /dev/snd -p 5901:5901 image_name

1 Like