Update Dockerfile

Dockerfile

@@ -10,7 +10,7 @@ WORKDIR /tmp/napalm-onyx
 RUN /opt/netbox/venv/bin/pip3 install pip==20.0.2 && \
     /opt/netbox/venv/bin/pip3 install . && \
     rm -rf /tmp/napalm-onyx
-RUN useradd -k -g netbox -u 1000 netbox
+RUN adduser -k --uid 1000 netbox
 USER netbox
 RUN SECRET_KEY="dummy" /opt/netbox/venv/bin/python /opt/netbox/netbox/manage.py collectstatic --no-input