Remove the ubuntu user from the base image.

docker/Dockerfile

@@ -11,7 +11,8 @@ RUN apt update -y && \
 
 # Set up user.
 # Touch file in home directory so we don't get bothered first call to sudo
-RUN useradd -m -G sudo -s /bin/bash -u 1000 j7s && \
+RUN userdel -r ubuntu && \
+    useradd -m -G sudo -s /bin/bash -u 1000 j7s && \
     bash -c 'echo "%sudo  ALL=(ALL)       NOPASSWD: ALL" >> /etc/sudoers.d/container' && \
     chmod 0440 /etc/sudoers.d/container && \
     touch /home/j7s/.sudo_as_admin_successful