title: Read-only file system when attempting mkdir /data/db on Mac
body: <p>I am trying to create a new folder in the main directory </p>
  
  <p>Tried all kinds of examples</p>
  
  <p><code>sudo mkdir /data/db</code> </p>
  
  <p><code>sudo mkdir -p /data/db</code> </p>
  
  <p>I keep getting </p>
  
  <blockquote>
    <p>mkdir: /data: Read-only file system</p>
  </blockquote>