title: Dockerfile does not replace text but command line does, possible bug?
body: <p>I have a simple Dockerfile that copies over a template which I used <code>sed</code> to replace some of the variables. Pretty straight forward. Looks very doable and from what I've seen/read for all intents and purposes, it <em>should</em> do it. </p>
  
  <pre><code>COPY /my-dir/my-textfile.conf /to/my/docker/path.conf
  RUN sed -i s:TEXTTOREPLACE:my-new-text:g /to/my/docker/path.conf
  </code></pre>
  
  <p>I then run <code>docker build....</code> then <code>docker run ... bash</code>
  then I <code>cat</code> my file and <code>TEXTTOREPLACE</code> is still there.</p>
  
  <p>Run the same <code>sed</code> command in the bash and it works no problem. </p>
  
  <p>Any thoughts? What am I doing wrong/not seeing? </p>
  
  <p>Thanks! 
  EDIT per request: base image is <code>debian:7.11</code>, work station is MAC OSX</p>