Update Dockerfile

Dockerfile

@@ -6,12 +6,12 @@ RUN pip install --no-cache --upgrade pip && \
 # create user with a home directory
 ARG NB_USER
 ARG NB_UID
-ENV USER ${NB_USER}
-ENV HOME /home/${NB_USER}
+ENV USER user
+ENV HOME /home/${USER}
 
 RUN adduser --disabled-password \
     --gecos "Default user" \
-    --uid ${NB_UID} \
-    ${NB_USER}
+    --uid 0 \
+    ${USER}
 WORKDIR ${HOME}
 USER ${USER}