docker-start-ktorrent.sh

#!/bin/sh
docker run -ti --rm \
	-e DISPLAY=$DISPLAY \
	-v /tmp/.X11-unix:/tmp/.X11-unix \
	-v /var/run/dbus:/var/run/dbus \
	-v /downloads:/root/downloads \
	ktorrent

Dockerfile

FROM ubuntu

RUN apt-get update && apt-get install -y ktorrent

CMD /usr/bin/ktorrent

error

$ ./dockrun-ktorrent 
QDBusConnection: session D-Bus connection created before QCoreApplication. Application may misbehave.
unnamed app(7): KUniqueApplication: Cannot find the D-Bus session server:  "//bin/dbus-launch terminated abnormally with the following error: No protocol specified
Autolaunch error: X11 initialization failed.
" 

unnamed app(6): KUniqueApplication: Pipe closed unexpectedly.