title: Pip install actually IN a docker container (Airflow)
body: <p>I am really new with docker. I have it run now for airflow. For one of the airflow DAGs, I perform <code>python jobs.&lt;job_name&gt;.run</code> which is located on the server + within the docker. However, this python code needs packages to run and I am having trouble installing those.</p>
  
  <p>If I put in the Dockerfile a <code>RUN pip install ...</code> it doesn't seem to work. If I go 'in' the docker container by <code>docker exec -ti &lt;name_of_worker&gt; bash</code> and I perform <code>pip freeze</code>, no packages show up.</p>
  
  <p>However, if I perform the pip install command while I am in the worker, the airflow DAG will run successfully. However, I  shouldn't have to perform this task every time I rebuild my containers. Can anyone help me?</p>