title: How to persist 'ln' in Docker with Ubuntu
body: <p>I have a Docker machine that I'm installing OpenCV 2.4.11</p>
  
  <p>However, there is an error happening that I indeed found a solution, but it's temporary.</p>
  
  <p>When I run my Python script that uses <code>cv2</code>, throws this error message:</p>
  
  <p><code>Error: libdc1394 error: Failed to initialize libdc1394</code></p>
  
  <p>I saw that this is the only thread that fixed my problem, but temporarily:
  <a href="https://stackoverflow.com/questions/12689304/ctypes-error-libdc1394-error-failed-to-initialize-libdc1394">ctypes error: libdc1394 error: Failed to initialize libdc1394</a></p>
  
  <p>I added the following line to my <code>Dockerfile</code>, but that didn't affected my VM. </p>
  
  <p><code>RUN ln /dev/null /dev/raw1394</code></p>
  
  <p>However, if I enter that command while the VM is running (<code>docker run -it ...</code>), it indeed makes things work! However, that doesn't solves my problem, because I need it to be ok on startup, and if I re-enter the VM, the problem comes back.</p>
  
  <hr>
  
  <p>My Dockerfile:</p>
  
  <pre><code># Pull base image.
  FROM library/ubuntu
  
  MAINTAINER Ivan Seidel &lt;ivanseidel@gmail.com&gt;
  
  RUN apt-get update
  
  #
  # Python
  #
  RUN apt-get install -y python python-dev python-pip python-virtualenv
  
  #
  # Node.js and NPM
  #
  RUN apt-get install -y nodejs nodejs-legacy npm git --no-install-recommends
  
  #
  # Install OpenCV
  #
  RUN apt-get install -y python-opencv --no-install-recommends
  RUN ln /dev/null /dev/raw1394
  
  #
  # Clear cache
  #
  RUN rm -rf /var/lib/apt/lists/*
  
  #
  # Specific data
  # 
  EXPOSE 80
  COPY . /data
  WORKDIR /data
  RUN npm install --production
  
  CMD ["bash"]
  </code></pre>