title: Docker not found when building docker image using Docker Jenkins container pipeline
body: <p>I have a Jenkins running as a docker container, now I want to build a Docker image using pipeline, but Jenkins container always tells Docker not found.</p>
  
  <pre><code>[simple-tdd-pipeline] Running shell script
  + docker build -t simple-tdd .
  /var/jenkins_home/workspace/simple-tdd-pipeline@tmp/durable-
  ebc35179/script.sh: 2: /var/jenkins_home/workspace/simple-tdd-
  pipeline@tmp/durable-ebc35179/script.sh: docker: not found
  </code></pre>
  
  <p>Here is how I run my Jenkins image:</p>
  
  <pre><code>docker run --name myjenkins -p 8080:8080 -p 50000:50000 -v 
  /var/jenkins_home -v /var/run/docker.sock:/var/run/docker.sock 
  jenkins
  </code></pre>
  
  <p>And the DockerFile of Jenkins image is:
  <a href="https://github.com/jenkinsci/docker/blob/9f29488b77c2005bbbc5c936d47e697689f8ef6e/Dockerfile" rel="noreferrer">https://github.com/jenkinsci/docker/blob/9f29488b77c2005bbbc5c936d47e697689f8ef6e/Dockerfile</a></p>