further x notes

experiment/production/Misc-Notes.md

@@ -153,6 +153,15 @@ root      3354  0.0  0.0   3872   788 tty1     S+   Jan30   0:00 xinit /home/bus
 root     27449  0.0  0.0   7348   524 pts/1    S+   05:48   0:00 grep xserver
 ```
 
+---
+
+From [an SO answer](https://unix.stackexchange.com/questions/209746/how-to-resolve-no-protocol-specified-for-su-user), need to load the 'magic cookie' for
+X communication:
+
+```
+su - <otheruser> -c "unset XAUTHORITY; xauth add $(xauth list)"
+```
+
 ### Packages
 
 ```