title: Docker RUN ls shows cached files
body: <p>I am trying to setup a docker container and am using <code>RUN ls</code> to help debug. However, when I run <code>RUN ls</code>, docker prints out the following:</p>
  
  <pre><code> ---&gt; Using cache
   ---&gt; 96223b1b0748
  </code></pre>
  
  <p>I am expecting it to log out files in the folder. Does anyone know what might be happening?</p>
  
  <p>Here is my full Dockerfile:</p>
  
  <pre><code>FROM node:latest 
  
  WORKDIR /app
  
  COPY app .
  
  RUN ls
  </code></pre>
  
  <p>Thanks in advance!</p>