title: Cannot run ruby commands while running Docker
body: <p>I have an image I have built with Ruby in it. I am able to run Ruby commands, <code>irb</code> and <code>install gems</code> in the image while running by:</p>
  
  <pre><code>docker run -it jikkujose/apple
  </code></pre>
  
  <p>I can also do this to list the files in the container:</p>
  
  <pre><code>docker run -it jikkujose/apple ls
  </code></pre>
  
  <p>But when I try to run Ruby commands, it fails:</p>
  
  <pre><code>docker run -it jikkujose/apple ruby -e "puts 'Hello'"
  </code></pre>
  
  <p>Error: </p>
  
  <pre><code>Error response from daemon: Cannot start container c888aa8d2c7510a672608744a69f00c5feda4509742d54ea2896b7ebce76c16d: [8] System error: exec: "ruby": executable file not found in $PATH
  </code></pre>