title: How unique is /dev/serial/by-id
body: <p>So, the question is, is the content of <code>/dev/serial/by-id</code> unique?</p>
  
  <p>Essentially the issue is I want to connect several (two or more) arduinos (potentially of different types, but they may all end up being leonardos) to the Raspberry Pi for the purposes of an automation system.</p>
  
  <p>I'll be using the serial interfaces to communicate between the Raspberry Pi in Python and the Arduinos. I've run this on one of the leonardos (at present I only have one):</p>
  
  <pre><code>udevadm info -a -n /dev/ttyACM0| grep serial  
  0000:00:1d.0
  </code></pre>
  
  <p>Is this a unique serial for my serial connection to the Pi? Can I rely on this to create a UDEV rule to assign a particular mount point, or does a unique and reliable mount point get already created in <code>/dev/serial/by-id/</code>, which I can use instead of hacked-udev rules?</p>