title: Understanding docker diff
body: <p>I do not understand the output of 'docker diff'. See below for details.
  This is my Docker version:</p>
  
  <pre><code>$ docker version
  Client version: 1.7.1
  Client API version: 1.19
  Go version (client): go1.4.2
  Git commit (client): 786b29d
  OS/Arch (client): linux/amd64
  Server version: 1.7.1
  Server API version: 1.19
  Go version (server): go1.4.2
  Git commit (server): 786b29d
  OS/Arch (server): linux/amd64
  </code></pre>
  
  <p>I have a Jenkins image with the following content in /var/jenkins_home:</p>
  
  <pre><code>$ docker run -it --rm jenkins ls /var/jenkins_home
  init.groovy.d
  </code></pre>
  
  <p>I then start Jenkins to populate Jenkins data dir:</p>
  
  <pre><code>$ docker run --name app -d jenkins
  </code></pre>
  
  <p>After Jenkins is started I call into the container to list the files:</p>
  
  <pre><code>$ docker exec app ls /var/jenkins_home
  Download metadata.log
  hudson.model.UpdateCenter.xml
  identity.key.enc
  init.groovy.d
  jobs
  nodeMonitors.xml
  nodes
  plugins
  secret.key
  secret.key.not-so-secret
  secrets
  updates
  userContent
  </code></pre>
  
  <p>Ok! Lots of new files. Now I want to ask Docker what files are changed or created:</p>
  
  <pre><code>$ docker diff app
  C /tmp
  A /tmp/hsperfdata_jenkins
  A /tmp/hsperfdata_jenkins/1
  A /tmp/jetty-0.0.0.0-8080-war--any-
  A /tmp/jffi6440203232202129886.tmp
  A /tmp/jna--1712433994
  A /tmp/winstone874928832634242220.jar
  C /var
  C /var/log
  C /var/log/copy_reference_file.log
  </code></pre>
  
  <p>So why is it that 'docker diff' isn't showing me the new files in '/var/jenkins_home'?
  What am I doing wrong?</p>
  
  <p>Best regards,
  - Morten Green Hermansen, Fanitas</p>