How to make Xvfb display visible?

问题:

I am running selenium through Xvfb on display number :99 like this:

/usr/bin/Xvfb :99 -ac -screen 0 1024x768x8 & export DISPLAY=":99" && java -jar /usr/lib/selenium/selenium-server-standalone-2.24.1.jar -port 4444

However display with number other than :0 is not visible by default. How do I make it visible to actually see what selenium is doing in the browser?

回答1:

It's virtual. From the man page Xvfb(1):

Xvfb is an X server that can run on machines with no display hardware and no physical input devices. It emulates a dumb framebuffer using virtual memory.

Also in the man page:

Xvfb -pixdepths 3 27 -fbdir /var/tmp The server will listen for connections as server number 0, will have the default screen configuration (one screen, 1280x1024x8), will also support pixmap depths of 3 and 27, and will use memory mapped files in /var/tmp for the framebuffer.

xwud -in /var/tmp/Xvfb_screen0 Displays screen 0 of the server started by the preceding example.

回答2:

You can get a live view by running a VNC server against the Xvfb display, like this:

x11vnc -display :99 -localhost &
vncviewer :0

回答3:

All you need is to install x11vnc via:

sudo apt-get install x11vnc xvfb fluxbox

^{Optionally install fluxbox to have simple window manager.}

---

Then to setup access to Xvfb for remote control, you can use X11 over SSH or VNC over SSH, e.g.

export DISPLAY=:1
Xvfb $DISPLAY -screen 0 1024x768x16 &
fluxbox &
x11vnc -display $DISPLAY -bg -forever -nopw -quiet -listen localhost -xkb

Here is script friendly version:

export DISPLAY=${DISPLAY:-:0} # Select screen 0 by default.
xdpyinfo
if which x11vnc &>/dev/null; then
  ! pgrep -a x11vnc && x11vnc -bg -forever -nopw -quiet -display WAIT$DISPLAY &
fi
! pgrep -a Xvfb && Xvfb $DISPLAY -screen 0 1024x768x16 &
sleep 1
if which fluxbox &>/dev/null; then
  ! pgrep -a fluxbox && fluxbox 2>/dev/null &
fi
echo "IP: $(hostname -I) ($(hostname))"

^{Note: I'm using it in the following Docker project (check .funcs.cmds.inc.sh).}

If your Xvfb listen on localhost only, you can setup tunneling to localhost, so a vncviewer can then connect to localhost to get remote control over the server. E.g.

ssh -N -T -L 5900:localhost:5900 user@remotehost &
vncviewer -encodings 'copyrect tight zrle hextile' localhost:5900

Or to listen on all addresses with password, use:

x11vnc -display :0.0 -usepw

^{To setup password, run: x11vnc -storepasswd.}

See: Remote control over SSH at Xvfb Wikipedia page

---

Or you can use the following one-liner:

$ x11vnc -create -env FD_PROG=/usr/bin/fluxbox \
    -env X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 \
        -env X11VNC_CREATE_GEOM=${1:-1024x768x16} \
        -gone 'killall Xvfb' \
        -bg -nopw

• -create makes it start Xvfb
• X11VNC_FINDDISPLAY_ALWAYS_FAILS=1 makes it goto the created Xvfb session (Display :1 rather than :0 which will be normal desktop)
• FD_PROG=/usr/bin/fluxbox makes it fire up Fluxbox (Ubuntu's one, should have background Ubuntu logo)
• X11VNC_CREATE_GEOM=${1:-1024x768x16} sets screen to 16bit colour 1024x768
• -gone cleans up when it exits as otherwise Xvfb is left behind (killing xvfb also kills fluxbox)

Check also:

• Using VNCserver + GUI application + Virtual Display in Docker container
• Ubuntu Fluxbox GUI with x11vnc and Xvfb

回答4:

A simple solution is also to constantly take screenshots of the program like this:

while /bin/true; do
    DISPLAY=:99 import -window root ~/Pictures/xvfb_screenshot.png
    sleep 0.1
done &
PID=$!
feh --reload 0.1 ~/Pictures/xvfb_screenshot.png 2>/dev/null
kill $PID

Note: requires to install imagemagick and feh