title: Jenkins pipeline issue with Docker
body: <p>When I was trying to run a Jenkins pipeline project, it failed giving this message under the "docker pull node:6-alpine": </p>
  
  <pre><code>&lt;.jenkins/workspace/simple-node-js-react-npm-app@tmp/durable-431710c5/script.sh: line 2: docker: command not found
  
  script returned exit code 127&gt;
  </code></pre>
  
  <p>I have no idea what's going on here, and I couldn't access the directory mentioned in the error. I am pretty new to Jenkins.</p>