title: How to install ffmpeg for ubuntu using command line?
body: <p>A lit background...
  This is a piece of code in my Dockerfile. I want to deploy my app to google app engine. Somehow I couldn't install ffmpeg. </p>
  
  <pre><code>ENV VIRTUAL_ENV /env
  ENV PATH /env/bin:$PATH
  RUN apt-get install ffmpeg
  </code></pre>
  
  <p>This is error log:</p>
  
  <pre><code>E: Unable to locate package ffmpeg
  The command '/bin/sh -c apt-get install ffmpeg' returned a non-zero code: 100
  ERROR
  ERROR: build step "gcr.io/cloud-builders/docker@sha256:ef2e6744a171cfb0e8a0ef27f9b9a34970341bfc0c3d401afdeedca72292cf73" failed: exit status 100
  </code></pre>
  
  <p>I found this but it didn't work for me. It complained about <strong>add-apt-repository</strong> is not valid command.
  <a href="https://askubuntu.com/questions/691109/how-do-i-install-ffmpeg-and-codecs">https://askubuntu.com/questions/691109/how-do-i-install-ffmpeg-and-codecs</a></p>
  
  <p>Anyone can help me with this? Thanks!!!</p>