title: Error: can't chdir to 'app' when using docker start container
body: <p>I have build a simple Flask app and I am trying to run it on Docker but I get this error when starting the container: <code>Error: can't chdir to 'app'</code></p>
  <p>The app runs fine when i start it from cmd but when I try to start the docker container for the image i created it gives the above error.</p>
  <p>Here is the Docker file:</p>
  <pre><code>FROM python:3.6.12-alpine
  COPY requirements.txt /
  RUN pip3 install -r /requirements.txt
  
  COPY . /app
  WORKDIR /app
  RUN chmod 777 /app
  
  ENTRYPOINT [&quot;./gunicorn.sh&quot;]
  </code></pre>
  <p>I am trying to run it with gunicorn web server. In my requirements file i have flask and gunicorn and for the python app I have just one file and here is the code:</p>
  <pre><code>from flask import Flask
  app = Flask(__name__)
  
  @app.route('/')
  def hello_world():
  return 'Hello, World!'
  </code></pre>
  <p>I am doing the following steps to build the image and container:</p>
  <ol>
  <li>docker build -t flask .</li>
  <li>docker run -d -p 80:80 flask</li>
  <li>docker start -ai (id of the container)</li>
  <li>I get the error that I mentioned -&gt; Error: can't chdir to 'app'</li>
  </ol>
  <p>Can someone give me an ideea why the container is not starting and it is giving me this error? Thanks</p>