another try

docker/Dockerfile

@@ -78,7 +78,7 @@ RUN python3 -m pip install ipython
 RUN apt-get install -y tk # for dawn
 
 # add jupyter packages for UC2 on top so they don't need to be installed every time
-RUN python3 -m pip install jupyterlab jupyterhub==3.1.1 batchspawner
+RUN python3 -m pip install jupyterlab jupyterhub==4.1.5 batchspawner
 RUN ln -s /usr/bin/python3 /usr/bin/python
 
 
@@ -98,19 +98,29 @@ RUN cd  /root/minicalosim && git checkout $COMMIT && \
     cp minicalo* ../bind/G4Calo.py /usr/local/lib/python3.8/dist-packages/
 
 
-CMD ["start-notebook.py"]
 
 RUN cp /root/minicalosim/docker/start-notebook.py /usr/local/bin/
 RUN cp /root/minicalosim/docker/start-notebook.sh /usr/local/bin/
 RUN cp /root/minicalosim/docker/start-singleuser.py /usr/local/bin/
 RUN cp /root/minicalosim/docker/start-singleuser.sh /usr/local/bin/
+RUN cp /root/minicalosim/docker/fix-permissions /usr/local/bin/
 
-#USER root
-##RUN fix-permissions /etc/jupyter/
+ARG NB_USER="jovyan"
+ARG NB_UID="1000"
+ARG NB_GID="100"
+
+USER root
+
+#RUN groupadd -g ${NB_GID} ${NB_USER} && \
+RUN    useradd -m -s /bin/bash -N -u ${NB_UID} -g ${NB_GID} ${NB_USER}
+
+RUN mkdir /etc/jupyter
+RUN fix-permissions /etc/jupyter/
 
 
 # clean up
 RUN rm -rf /root/minicalosim
 
-#USER ${NB_UID}
+USER ${NB_UID}
+CMD ["start-notebook.sh"]