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x11vnc

README.md

RENKU-VNC

1 Jupyter Server Proxy, NoVNC, Websockify, x11vnc, Xvfb or Xdummy

1.1 Usage

  • Build the image in this folder: docker build -t renku-vnc .

  • Start the docker container: docker run --rm -it -p 8888:8888 renku-vnc jupyter lab --ip=0.0.0.0

  • Open the jupyter lab page at the URL provided in the output, or copy the token http://127.0.0.1:8888/?token=...

  • Open the HTML vnc viewer on localhost:8888/vnc

1.2 Implementation details

  • Install X virtual frame buffer (Xvfb), the VNC server (x11vnc), and net-tools (netstat)
apt-get update
apt-get install -y --no-install-recommends xterm xvfb x11vnc net-tools
  • Install the window manager, and X utilities (xrandr, xset). We use fluxbox, but other choices such as openbox, xfce4 are also possible.
apt-get update
apt-get install -y fluxbox x11-xserver-utils

Note that we are only aiming for a functional windows or desktop environment that can be used for testing purpose. Therefore this install lacks the obvious bells and whistles customizations. See the documentation on the available windows manager or full fledge desktop managers for more information.

  • Install novnc and its sister project websockify from github
mkdir -p /usr/share/novnc
git clone https://github.com/novnc/noVNC /tmp/novnc
mv /tmp/novnc/{app,utils,core,vendor,package.json} /tmp/novnc/*.html /usr/share/novnc
mkdir -p /usr/share/novnc/utils/websockify
git clone https://github.com/novnc/websockify /tmp/ws
mv /tmp/ws/{websockify,run,websockify.py} /usr/share/novnc/utils/websockify
chmod a+rX -R /usr/share/novnc
  • Set the path for NoVNC's websockify.
sed -i -e "s,'websockify',document.location.pathname.slice(1),g" /usr/share/novnc/app/ui.js
sed -i -e "s,'websockify',document.location.pathname.slice(1),g" /usr/share/novnc/vnc_lite.html
  • Copy and soft-link vnc_renku.html to index.html so that we land on it from the jupyter lab's VNC launcher
COPY --chown=root:root vnc_renku.html /usr/share/novnc/
RUN ln -s /usr/share/novnc/vnc.html /usr/share/novnc/index.html

This file is a modified version of vnc_lite.html, with support for renku - (1) it automatically set the path to NoVNC's websockify, (2) it shows the URL of the project's interactive environment in the status bar, and (3) it has support for full screen mode.

conda install jupyter-server-proxy -c conda-forge
jupyter labextension install @jupyterlab/server-proxy
  • Copy the startup scripts into /starvnc to start xvfb, x11vnc and novnc:
(x11vnc -env FD_OPTS="-nolisten tcp -c r" \
            -env FD_GEOM="1024x768x24" \
            -env FD_PROG="/usr/bin/startfluxbox" \
            -display WAIT:cmd=FINDCREATEDISPLAY-Xvfb \
            -no6 \
            -noipv6 -noxdamage -noxfixes -noxrecord \
            -rfbport ${vncport} \
            -ping 5 \
            -repeat \
            -forever -nevershared -nopw -o /tmp/x11vnc.log & ) &
(/usr/share/novnc/utils/launch.sh --vnc localhost:${vncport} --listen ${wsport} > /tmp/novnc.log 2>&1 & ) &

The x11vnc server will automatically look for an available display, and start Xvfb to create one if none exists (-display argument). The environment variables FD_OPTS and FD_GEOM can be used to pass additional arguments to the Xvfb process.

Modify FD_PROG to start the window manager of your choice.

X11vnc is configured to work in an endless loop (-forever) and allow a single client at the time (-nevershared), disconnecting existing clients when a new client (websockify proxy) connects. All communications between the jupyter lab proxy and Xvfb are unencrypted and password-less (-nopw) since they all happen inside the user's container and are protected to the jupyter lab proxy endpoint.

See the Xvfb and x11vnc documentation for other tuning parameters.

Keep in mind however that we don't have root/sudo priviledges in containers started by renkulab. Our startup script must work as a powerless $NB_USER userid.

  • Configure the jupyter lab server proxy extension to automatically invoke the /startvnc script when accessing the vnc/ path on the jupyter lab's URL.

In ~/.jupyter/jupyter_notebook_config.py copy paste the lines:

c.ServerProxy.servers = {
     'vnc': {
         'command': ['/startvnc', '{port}'],
         'timeout' : 10,
         'absolute_url': False,
         'new_browser_tab': True,
         'launcher_entry' :  {
            'enabled': True,
            'title': 'VNC'
     }
}

Jupyter proxy server will specify the {port} number. This is the port on which the VNC server or novnc's websockify proxy must listen to.

It is possible to also specify an icon for the VNC launcher in launcher_entry. See the Jupyter server proxy documentation for details.