/etc/init.d/xvfb service script

xvfb

#! /bin/sh

### BEGIN INIT INFO
# Provides:          Xvfb
# Required-Start:    $local_fs $remote_fs
# Required-Stop:
# X-Start-Before:    
# Default-Start:     2 3 4 5
# Default-Stop:
### END INIT INFO

XVFB=/usr/bin/Xvfb
XVFB_ARGS=":1 -ac -screen 1 1600x1200x24"
XVFB_LOG=/var/log/xvfb

case "$1" in
  start)
    echo -n "Starting Xvfb: "
    $XVFB $XVFB_ARGS 1>&2 2> $XVFB_LOG &
    echo "OK"
    ;;
  stop)
    echo -n "Stopping Xvfb: "
    killall Xvfb
    echo "OK"
    ;;
  restart)
    $0 stop
    $0 start
    ;;
  *)
    echo "Usage: /etc/init.d/xvfb {start|stop|restart}"
    exit 1
    ;;
esac

exit 0

On ubuntu 14.04 you'll have to first:

apt-get install xvfb psmisc