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
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