Well, I do have the GUACAMOLE_HOME variable set in /etc/environment. There's a single line in that file: "GUACAMOLE_HOME=/etc/guacamole" that ensures that environment variable is set at boot and I can verify with the "env" command. And I can assure you that both the mysql & Duo extension .jar files are in the same directory "/etc/guacamole/extensions"...
AAAAND I'm an idiot... I forgot to extract the downloaded extension file for Duo, leaving it as a .tar.gz Once I extracted the .jar file, restarted Jetty, everything worked! Thank you, Mike, for getting me to do some simple troubleshooting that I should have done myself :D -- Sent from: http://apache-guacamole-general-user-mailing-list.2363388.n4.nabble.com/