Clean up package caches and such

docker/gui/fedora-30/Dockerfile

@@ -16,6 +16,7 @@ RUN echo "mate-session &"> ~/.vnc/xstartup
 # RUN echo "startlxde &"> ~/.vnc/xstartup
 
 RUN sudo dnf -y remove *screensaver*
+RUN sudo dnf clean all 
 
 RUN chmod u+x ~/.vnc/xstartup
 RUN echo "password" | vncpasswd -f >> ~/.vnc/passwd

docker/gui/ubuntu-18.04/Dockerfile

@@ -12,6 +12,7 @@ RUN apt-get install -y \
 #        ubuntu-mate-desktop
 
 RUN apt-get remove -y "*screensaver*"
+RUN apt-get clean
 
 USER ${USER}:${USER}
 RUN touch ~/.Xauthority; \