title: Unable to run cygwin in Windows Docker Container
body: <p>I've been working with Docker for Windows, attempting to create a Windows Container that can run cygwin as the shell within the container itself. I haven't had any luck getting this going yet. Here's the Dockerfile that I've been messing with.</p>
  
  <pre><code># escape=`
  FROM microsoft/windowsservercore
  
  SHELL ["powershell", "-command"]
  
  RUN Invoke-WebRequest https://chocolatey.org/install.ps1 -UseBasicParsing | Invoke-Expression
  RUN choco install cygwin -y
  RUN refreshenv
  RUN [Environment]::SetEnvironmentVariable('Path', $env:Path + ';C:\tools\cygwin\bin', [EnvironmentVariableTarget]::Machine)
  </code></pre>
  
  <p>I've tried setting the ENTRYPOINT and CMD to try and get into cygwin, but neither seems to do anything. I've also attached to the container with <code>docker run -it</code> and fired off the cygwin command to get into the shell, but it doesn't appear to do anything. I don't get an error, it just returns to the command prompt as if nothing happened.</p>
  
  <p>Is it possible to run another shell in the Windows Container, or am I just doing something incorrectly?</p>
  
  <p>Thanks!</p>