title: How to make ffmpeg available inside my Docker container?
body: <p>I'm currently trying to run a <code>ffmpeg</code> Docker image inside my own container with <code>docker-compose</code> using the <code>depends_on</code> clause. But when I try to reach <code>ffmpeg</code> inside my code, it seems like it's not available system-wide and I get an error. I believe I'm misconfiguring Docker.</p>
  
  <p>My current <code>Dockerfile</code> is as follows:</p>
  
  <pre><code>FROM node:9
  
  WORKDIR /usr/app
  
  COPY package*.json ./
  
  RUN npm install --quiet
  
  COPY . .
  </code></pre>
  
  <p>And my <code>docker-compose.yml</code>:</p>
  
  <pre><code>version: '3'
  services:
    app:
      build: .
      command: npm run dev
      volumes:
      - .:/usr/app/
      - /usr/app/node_modules
      ports:
        - "3000:3000"
      depends_on:
        - ffmpeg
    ffmpeg:
      image: jrottenberg/ffmpeg:3.3
  </code></pre>
  
  <p>When I run <code>docker-compose up</code> I can see that the <code>ffmpeg</code> is actually working, but then my application proceeds to start and it seems that <code>ffmpeg</code> ceases to work.</p>