updates to BBB docs re autostart

Author: Dave Conway-Jones

docs/hardware/beagleboneblack.md

@@ -21,6 +21,14 @@ To start Node-RED
 
     sudo service node-red start
 
+To set Node-RED to auto-run on every boot
+
+    sudo systemctl enable node-red.service
+
+and likewise to stop it auto-running on boot
+
+    sudo systemctl disable node-red.service
+
 
 The 2GB console version suitable for flashing to older eMMC versions of the BBB will need to be manually installed as per below.
 
@@ -42,6 +50,18 @@ both Node.js and Node-RED in different locations and will conflict with and brea
 
 ---
 
+#### Configuring
+
+The Beaglebone is configured by default to run Node-RED as root. Therefore the configuration files are located in the
+`/root/.node-red` directory and you will need root privileges (sudo) to edit them. This is where you need to edit your
+`settings.js` file for example.
+
+Beaglebone also has a systemd service, `/lib/systemd/system/node-red.socket`, that automatically starts Node-RED
+when is sees an attempt to connect. By default this is port 1880 - but if you want change that you need to change it
+here as well as in the `settings.js` file.
+
+---
+
 ### Manual installation
 
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