docker-vnc-xfce4

Description

How to run a GUI application inside a docker container, and to access the application within a browser.
The easiest combo is to run

• Xvfb a virtual X server that can run on machines with no display hardware and no physical input devices. It emulates a dumb framebuffer using virtual memory
• a VNC server to be able to access from everywhere
• noVNC + websockify that allow to do VNC through a browser
• pulseaudio to share audio device
• a Window manager (see just below)

into an Ubuntu base image.

It is possible to choose any windows manager, but some are lighter than others. Below, there will be two simple examples with light ones:

• ratpoison
• Xfce

The final image size is 1.7Go.

Build the docker image

When building the image it is possible to specify a personal timezone

docker build .                \
  --file Dockerfile           \
  --tag docker-vnc-xfce4      \
  --build-arg TZ=Europe/Paris

It takes few minutes to make it.

Usage

The built image expose standard ports:

• 22 for ssh connections
• 5900 for VNC access (here are VNC clients)
• 6080 for noVNC website

So that for browser access the full address is http://localhost:6080/vnc.html.
Applications starts with a simple user context: user (with password user01), and this user has sudo priviledges. User, password and uid/gid can be customized at startup with variables (see configuration below).

Start docker+vnc+xfce4

The most simple startup command is

docker run --rm                    \
  --interactive                    \
  --tty                            \
  --publish 6080:6080              \
  --publish ${VNC_PORT:-5900}:5900 \
  --publish ${SSH_PORT:-22}:22     \
  --name desktop                   \
  --env LANG=fr_FR.UTF-8           \
  --env USR_UID=$(id -u)           \
  --env USR_GID=$(id -g)           \
  docker-vnc-xfce4

Configuration

Some variables can be passed to the docker run command to modify image behavior.

Name	Description
DESKTOP_ADDITIONAL_PROGRAMS	Automatically starts a program (ratpoison only)
DESKTOP_BACKGROUND_IMAGE	Default background image (can be an url)
DESKTOP_ENV	Choose desktop environment (between ratpoison and xfce4)
DESKTOP_KEYBOARD_LAYOUT	Specify default keyboard layout (format: layout/variant)
DESKTOP_SIZE	Define the screen size (default 1280x1024)
DESKTOP_THEME	Set the default Xfce4 theme
DESKTOP_VNC_PASSWORD	Set a VNC password (default is none)
USR	The username that runs the VNC server (default is user)
USR_GID	The gid (group id) of the user USR (default is 6000)
USR_PASS	The password of the default user (default is user01)
USR_UID	The uid (user id) of the user USR (default is 6000)

Example: run Xfce4 in french, with desktop personal settings and sound

docker run --rm                                                                                               \
  --interactive                                                                                               \
  --tty                                                                                                       \
  --volume /run/user/$(id -u)/pulse/native:/run/user/1000/pulse/native                                        \
  --privileged                                                                                                \
  --publish 6080:6080                                                                                         \
  --publish ${VNC_PORT:-5900}:5900                                                                            \
  --publish ${SSH_PORT:-22}:22                                                                                \
  --name desktop                                                                                              \
  --env DESKTOP_ENV=xfce4                                                                                     \
  --env LANG=fr_FR.UTF-8                                                                                      \
  --env DESKTOP_KEYBOARD_LAYOUT="fr/azerty"                                                                   \
  --env DESKTOP_SIZE="1920x1080"                                                                              \
  --env DESKTOP_THEME="Greybird-dark"                                                                         \
  --env DESKTOP_BACKGROUND_IMAGE="https://upload.wikimedia.org/wikipedia/commons/9/96/Alberi_AlpediSiusi.JPG" \
  --env USR_UID=$(id -u)                                                                                      \
  --env USR_GID=$(id -g)                                                                                      \
  docker-vnc-xfce4 /bin/bash

In the ratpoison example a firefox browser is started in the image.

To use another application it is necessary to

• first install it, either
  • in Dockerfile at line 96: RUN apt-get install ... notepadqq (here we add notepadqq)
  • by setting variable INSTALL_ADDITIONAL_PROGRAMS at run
• then run it, by setting it in variable DESKTOP_ADDITIONAL_PROGRAMS

Example: run ratpoison with spider cards games in an interactive container

docker run --rm                                                             \
  --interactive                                                             \
  --tty                                                                     \
  --privileged                                                              \
  --publish 6080:6080                                                       \
  --publish ${VNC_PORT:-5900}:5900                                          \
  --publish ${SSH_PORT:-22}:22                                              \
  --name desktop                                                            \
  --env LANG=fr_FR.UTF-8                                                    \
  --env DESKTOP_ENV=ratpoison                                               \
  --env DESKTOP_SIZE="1024x800"                                             \
  --env INSTALL_ADDITIONAL_PROGRAMS=aisleriot                               \
  --env DESKTOP_ADDITIONAL_PROGRAMS="/bin/sh -c '/usr/games/sol -v spider'" \
  --env USR_UID=$(id -u)                                                    \
  --env USR_GID=$(id -g)                                                    \
  docker-vnc-xfce4 /bin/bash

For more informations on ratpoison desktop manager see general use page.

SSL specifics

This image is designed to accept private CA certificates. Just mount them in /usr/local/share/ca-certificates directory, and they will be loaded at startup.

Startup alternatives

It is possible to customize image statup by mounting scripts into the container:

• /prestartup.sh: if present this script is executed at very begining of the entrypoint script before anything else (even before user creation)
• /poststartup.sh: if present this script is executed at the end of the entrypoint script just before waiting for connections
• /startup.sh: if present this script is executed at the end of the entrypoint script to wait for connections

Examples